Download SQA CfE Higher Human Biology Unit 3

SCHOLAR Study Guide
SQA CfE Higher Human Biology
Unit
3:
Neurobiology
and
Communication
Authored by:
Eoin McIntyre
Reviewed by:
Sheena Haddow
Previously authored by:
Mike Cheung
Eileen Humphrey
Eoin McIntyre
Jim McIntyre
Heriot-Watt University
Edinburgh EH14 4AS, United Kingdom.
First published 2014 by Heriot-Watt University.
This edition published in 2014 by Heriot-Watt University SCHOLAR.
Copyright © 2014 Heriot-Watt University.
Members of the SCHOLAR Forum may reproduce this publication in whole or in part for
educational purposes within their establishment providing that no profit accrues at any stage,
Any other use of the materials is governed by the general copyright statement that follows.
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system
or transmitted in any form or by any means, without written permission from the publisher.
Heriot-Watt University accepts no responsibility or liability whatsoever with regard to the
information contained in this study guide.
Distributed by Heriot-Watt University.
SCHOLAR Study Guide Unit 3: SQA CfE Higher Human Biology
1. SQA CfE Higher Human Biology
ISBN 978-1-909633-18-6
Printed and bound in Great Britain by Graphic and Printing Services, Heriot-Watt University,
Edinburgh.
Acknowledgements
Thanks are due to the members of Heriot-Watt University's SCHOLAR team who planned and
created these materials, and to the many colleagues who reviewed the content.
We would like to acknowledge the assistance of the education authorities, colleges, teachers
and students who contributed to the SCHOLAR programme and who evaluated these materials.
Grateful acknowledgement is made for permission to use the following material in the
SCHOLAR programme:
The Scottish Qualifications Authority for permission to use Past Papers assessments.
The Scottish Government for financial support.
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only and are trademarks, registered trademarks or service marks of their respective holders.
i
Contents
1 The structure of the nervous system
1.1 Introduction . . . . . . . . . . . . .
1.2 Divisions of the nervous system . .
1.3 Parts of the brain . . . . . . . . . .
1.4 Learning points . . . . . . . . . . .
1.5 Extended response question . . .
1.6 End of topic test . . . . . . . . . .
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2 Perception and memory
2.1 Perception . . . . . . . . . . .
2.2 Memory . . . . . . . . . . . .
2.3 A note about techniques . . .
2.4 Learning points . . . . . . . .
2.5 Extended response question
2.6 End of topic test . . . . . . .
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3 Neurons, neurotransmitters and neural pathways
3.1 Neurons . . . . . . . . . . . . . . . . . . . . . .
3.2 Glial cells and myelination . . . . . . . . . . . .
3.3 Neurotransmitters . . . . . . . . . . . . . . . .
3.4 Neural pathways . . . . . . . . . . . . . . . . .
3.5 Learning points . . . . . . . . . . . . . . . . . .
3.6 Extended response question . . . . . . . . . .
3.7 End of topic test . . . . . . . . . . . . . . . . .
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4 Neurotransmitters, mood and behaviour
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . .
4.2 Dopamine and the reward pathway . . . . . . . . . . .
4.3 Endorphins . . . . . . . . . . . . . . . . . . . . . . . .
4.4 Neurotransmitter-related disorders and their treatment
4.5 Mode of action of recreational drugs . . . . . . . . . .
4.6 Drug addiction, sensitisation and tolerance . . . . . .
4.7 Learning points . . . . . . . . . . . . . . . . . . . . . .
4.8 Extended response question . . . . . . . . . . . . . .
4.9 End of topic test . . . . . . . . . . . . . . . . . . . . .
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5 Infant attachment and the effect of communication
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2 Forms of infant attachment . . . . . . . . . . . . . . . . . . . . . . . . .
5.3 Long period of dependency . . . . . . . . . . . . . . . . . . . . . . . . .
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ii
CONTENTS
5.4
5.5
5.6
5.7
5.8
5.9
The effect of communication .
Non-verbal communication .
Verbal communication . . . .
Learning points . . . . . . . .
Extended response question
End of topic test . . . . . . .
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6 The effect of experience and social influences
6.1 Introduction . . . . . . . . . . . . . . . . . .
6.2 The effect of practice on motor skills . . . .
6.3 Imitation . . . . . . . . . . . . . . . . . . . .
6.4 Trial and error learning . . . . . . . . . . . .
6.5 Generalisation and discrimination . . . . . .
6.6 Social facilitation and deindividuation . . . .
6.7 Influences that change beliefs . . . . . . . .
6.8 Learning points . . . . . . . . . . . . . . . .
6.9 Extended response question . . . . . . . .
6.10 End of topic test . . . . . . . . . . . . . . .
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7 End of unit test
145
Glossary
149
Answers to questions and activities
1
The structure of the nervous system . . . . . . . .
2
Perception and memory . . . . . . . . . . . . . . .
3
Neurons, neurotransmitters and neural pathways .
4
Neurotransmitters, mood and behaviour . . . . . .
5
Infant attachment and the effect of communication
6
The effect of experience and social influences . .
7
End of unit test . . . . . . . . . . . . . . . . . . . .
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© H ERIOT-WATT U NIVERSITY
1
Topic 1
The structure of the nervous
system
Contents
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 Divisions of the nervous system . . . . . . . . . . . . . . . . . . . . . . . . . . .
2
4
1.2.1 Central and peripheral nervous systems . . . . . . . . . . . . . . . . . .
5
1.2.2 Autonomic nervous system . . . . . . . . . . . . . . . . . . . . . . . . .
1.3 Parts of the brain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8
10
1.3.1 The central core . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3.2 The limbic system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11
13
1.3.3 The cerebral cortex . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4 Learning points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14
21
1.5 Extended response question . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.6 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23
24
Learning Objectives
By the end of this topic, you should be able to:
• explain the general functions of the nervous system;
• describe the different divisions of the nervous system and their specific functions;
• describe the basic structure of the brain;
• state the functions of the central core, the limbic system and the cerebral cortex.
2
TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM
1.1
Introduction
Learning Objective
By the end of this section, you should be able to:
• state that the nervous system contains three types of neuron: sensory, motor
and interneurons;
• state that sensory neurons connect sense receptors with the central nervous
system;
• state that motor neurons connect the central nervous system to muscles or
glands;
• state that interneurons may connect with sensory, motor or other interneurons;
• state that the nervous system analyses sensory information from both the
external and internal environment;
• explain that the body stores some of this information which it uses to make
decisions about appropriate responses and behaviours;
• state that motor responses may be made by initiating muscular contractions or
glandular secretions.
Animals show two basic types of symmetry: radial symmetry, where there is an upper
and lower side, but no front or back, e.g. jellyfish; and bilateral symmetry, where there
are not only upper and lower surfaces, but a front and back as well, e.g. worms and
vertebrates. In the latter types of animal, there is usually a distinct 'head', or part of the
body which meets the world first, on which most external sense organs are clustered.
Sense organs are structures that contain receptors which respond to stimuli. These
stimuli can be changes in the external environment, which are detected as different
types of energy (e.g. light, sound, chemical, kinetic and heat), or changes in the internal
environment, e.g. changes in core temperature or the carbon dioxide level in the blood.
To be of any use, this information must be assessed and appropriate action taken in
response. This is done by neurons, of which there are three broad classes:
• sensory neurons, which connect sense receptors to the central nervous system;
• motor neurons, which connect the central nervous system to the muscles and
glands;
• interneurons (also known as relay, association or connector neurons), which are
found in the central nervous system and connect with sensory, motor, and other
interneurons.
When stimulated, neurons pass along their length a temporary reversal of the electrical
potential on their plasma membrane. These are called impulses and travel at velocities
between 1 and 100 m.s -1 . By locating many sense organs in the head and developing
the processing area of the central nervous system close to them, rates of reaction to
incoming stimuli can be maximised. The grouping of interneurons in the same area,
to form a brain, allows more interconnections and more complex processing, such as
© H ERIOT-WATT U NIVERSITY
TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM
learning and memory.
The extent to which learning plays an important part in animal behaviour depends very
much on the type of animal involved. Insects, which live for only a short period, may
never see their parents and only interact with others of their own species to mate.
Consequently, they rely almost entirely on inherited, innate patterns of behaviour to
identify food, escape predators, and find mates and places to lay eggs. There is no time
for insects to learn these things which means that the environment will weed out the less
successful life strategies by natural selection.
Long-lived animals, such as Primates (including humans), are social creatures with a
long dependent period, which means that there is ample opportunity for them to develop
responses which are based on their own experience and on the observation of others
(although it would be a mistake to think that innate responses play no role in Primate
behaviour).
Interestingly, the same type of behaviour may be innate in one group but learned in
others, e.g. mothering behaviour: a crocodile reared in isolation will still show the careful
attention to her young which is typical of the species, whereas chimpanzees (normally
the most attentive of mothers) when reared in isolation are most likely to reject their
offspring.
In summary, the nervous system provides animals with the means to collect, analyse
and respond appropriately to sensory information. These motor responses may take the
form of muscular contractions (e.g. reflexes such as knee-jerks or blinks) or secretions
from glands (e.g. adrenal or salivary glands).
Introduction to the structure of the nervous system: Questions
Q1: Sensory neurons connect sense organs to
a) the central nervous system
b) motor neurons
c) sensory neurons
..........................................
Q2: Motor neurons connect the central nervous system to
a) interneurons
b) muscles and glands
c) sense organs
..........................................
Q3: Interneurons are located in
a) the central nervous system
b) muscles
c) sense organs
..........................................
© H ERIOT-WATT U NIVERSITY
3
4
TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM
Q4:
Secretions by the adrenal gland are stimulated by
a) interneurons
b) motor neurons
c) sensory neurons
..........................................
Q5:
Storage of information is carried out by
a) interneurons
b) motor neurons
c) sensory neurons
..........................................
..........................................
1.2
Divisions of the nervous system
Learning Objective
By the end of this section, you should be able to:
• state that the nervous system is divided into the central and peripheral nervous
systems;
• state that the central nervous system comprises the brain and spinal cord;
• state that the peripheral nervous system is divided into the somatic and
autonomic nervous systems;
• state that the autonomic nervous system is further subdivided into the
sympathetic and the parasympathetic nervous systems.
The nervous system is sub-divided according to its structures and their functions.
© H ERIOT-WATT U NIVERSITY
TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM
5
Divisions of the nervous system: Question
Q6: Complete the labelling of the diagram using the words from the list.
Word list: autonomic, central, parasympathetic, peripheral, spinal cord.
..........................................
1.2.1
Central and peripheral nervous systems
Learning Objective
By the end of this section, you should be able to:
• state that the central nervous system consists of the spinal cord and the brain,
including the retinas of the eyes and the optic nerves;
• state that the peripheral nervous system comprises all sensory and motor
neurons outside the central nervous system;
• state that the peripheral nervous system comprises the somatic and autonomic
nervous systems;
• state that the somatic nervous system controls the voluntary movement of
skeletal muscles;
• explain that this control involves sensory neurons (e.g. connected to stretch
receptors in striped/striated muscle in leg) and motor neurons;
• state that the autonomic nervous system is responsible for involuntary
homeostatic control of many body functions;
• explain that this control involves sensory neurons (e.g. connected to stretch
receptors in smooth muscle of artery walls) and motor neurons;
• state that the motor neurons of the autonomic nervous system may connect to
smooth muscle (e.g. in the wall of the gut), cardiac muscle (e.g. pacemaker) or
glands (e.g. adrenal gland).
Scientists distinguish between the central nervous system (CNS) and the peripheral
nervous system (PNS). The CNS comprises the brain, including the retinas of the eyes
and optic nerves, and spinal cord, whereas the PNS consists of all the other parts, such
as the sensory and motor neurons. This is a purely structural division.
© H ERIOT-WATT U NIVERSITY
6
TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM
Central and peripheral nervous systems
The PNS is further divided functionally into the somatic and autonomic nervous
systems.
Somatic nerves control voluntary movement by controlling skeletal muscles. They
include sensory neurons and motor neurons. Sensory neurons send messages to
the CNS from the sensory receptors, mainly in the skin, whereas motor neurons take
messages to the muscles or glands causing them to function.
The autonomic system tends to control our basic activities, the ones that do not tend to
require conscious thought. You do not have to command,
"O heart, beat faster! I see my teacher yonder."
The autonomic system controls heart rate without conscious thought.
Nor do you need to decide to breathe faster when your homework is late. Heart rate,
breathing, peristalsis, and other similar functions are under the control of the autonomic
nervous system. Muscles under voluntary control have a striped (striated) appearance
like the fibres of a steak, whereas muscles under autonomic control are un-striped and
referred to as 'smooth muscle'. Cardiac muscle, which must never tire, appears like a
cross between striated muscle and the smooth muscle of the alimentary canal and
blood vessels.
© H ERIOT-WATT U NIVERSITY
TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM
7
The autonomic nervous system also controls endocrine glands which regulate growth
and the activities of other tissues. These include the pituitary, thyroid, pancreas and
adrenal glands.
Endocrine glands
5 min
Pituitary gland: sometimes called the master gland, the pituitary secretes many
hormones, e.g. growth hormone and ADH.
It also secretes hormones which control the activity of the other endocrine glands, e.g.
thyroid stimulationg hormone (TSH) stimulates the thyroid gland.
Thyroid gland: When stimulated by TSH from the pituitary, the thyroid gland secretes
the hormone thyroxine which regulates an individual's metabolic rate.
Parathyroid glands: these secrete parathyroid hormone, which regulates the level of
calcium in the blood.
Adrenal glands: the adrenal glands are situated on the upper surface of each kidney (ad
= at, renal = kidney).
They secrete many hormones the most well-known probably being adrenalin.
This hormone is involved in the 'fight or flight' mechanism which is triggered in response
to danger.
Ovary: found in females, ovaries produce the hormones oestrogen and progesterone
when stimulated by hormones from the pituitary gland.
© H ERIOT-WATT U NIVERSITY
8
TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM
The interplay between these hormones controls the menstrual cycle, including the
maturation and release of an ovum and the build up and break down of the lining of
the uterus.
Oestrogen also has a role in the development and maintenance of the female secondary
sexual characteristics.
Testis: found in males, testes produce hormones such as testosterone when stimulated
by hormones form the pituitary gland.
Testosterone is involved in the production of sperm and development and maintenance
of male secondary sexual characteristics.
..........................................
1.2.2
Autonomic nervous system
Learning Objective
By the end of this section, you should be able to:
• state that the autonomic nervous system (ANS) comprises the sympathetic and
parasympathetic nervous systems;
• state that the sympathetic and parasympathetic nervous systems act
antagonistically;
• state that the sympathetic nervous system prepares the body for action: 'fight
or flight';
• state that the parasympathetic nervous system returns the body to a relaxed,
standby condition: 'rest and digest';
• state that the sympathetic nervous system causes increases in heart and
breathing rates, and decreases in peristalsis and intestinal secretions;
• state that the parasympathetic system causes decreases in heart and breathing
rates, and increases in peristalsis and intestinal secretions.
The two branches of the autonomic nervous system, the sympathetic and the
parasympathetic, can be thought of as alert, 'fight or flight', and standby, 'rest and
digest', modes respectively. The former prepares the body for action and the latter
returns the organism to an energy-conserving state. Thus, the sympathetic and
parasympathetic nervous systems are described as antagonistic in action. This enables
the ANS to exert homeostatic control over many of the body's functions. This is
clearly observed in their effects on heart rate, breathing rate, peristalsis and intestinal
secretions.
© H ERIOT-WATT U NIVERSITY
TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM
Function
Sympathetic nerves
speed up - prepare for action
Parasympathetic nerves
calm down - conserve resources
Rate and force of contraction of
cardiac muscle increases.
Result: more blood to muscles.
Rate and force of contraction of
cardiac muscle decreases.
Result: less blood to muscles,
normal levels restored.
Breathing
rate
Muscles in bronchioles become
relaxed. Rate of contraction of
diaphragm and intercostal muscles
increases.
Result: increased gas exchange.
Muscles in bronchioles become
contracted. Rate of contraction of
diaphragm and intercostal
muscles decreases.
Result: reduced gas exchange.
Digestion
Rate of contraction of smooth
muscle in wall of digestive tract
decreases. Rate of blood flow to
digestive tract decreases.
Result: reduced digestion.
Rate of contraction of smooth
muscle in wall of digestive tract
increases. Rate of blood flow to
digestive tract increases.
Result: normal digestion.
Heart
rate
Adrenal
gland
9
Adrenal gland stimulated.
Result: secretion of hormone
adrenaline.
Summary of the influences of the Sympathetic and Parasympathetic Nervous Systems
Sympathetic and parasympathetic effects
5 min
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Autonomic nervous system: Question
Q7:
Enter either 'Increased' or 'Decreased' at the correct places in the table.
10 min
Sympathetic
Parasympathetic
Heart rate
Stroke volume
Breathing rate
Depth of breathing
Contractions of smooth
muscle of gut wall
Intestinal secretions
..........................................
1.3
Parts of the brain
Learning Objective
By the end of this section, you should be able to:
• state that the brain consists of three major regions: medulla, cerebellum and
cerebrum;
• state that the cerebrum comprises two interconnected hemispheres.
The vertebrate brain is the enlarged fore-end of the spinal cord, adapted to manage
the mass of sensory information coming in from the sense organs and the animal's
responses to it. In humans, this adaptation is taken to an incredibly complex level, but
the 'primitive' areas which run the body's machinery at a subconscious level are still
present (and, of course, essential). As the accompanying activity shows, the brain is
divided into three main areas: the medulla, the cerebellum and the cerebrum (which
consists of two interconnected cerebral hemispheres).
The human organism consists of several organ systems which function in a
coordinated way to respond to stimuli in the environment. Each organ system consists
of organs which, in turn, comprise groups of tissues. Tissues are assemblies of cells
with common functions. Every freshly-produced cell contains a nucleus which has all
the instructions to allow it to perform all cellular functions. However, to ensure that
chaos does not ensue, each nucleus only activates the genes necessary for it to
perform the functions of that tissue of which the cell is part.
Just as the nucleus controls cellular function, the nervous system coordinates organ
systems. It works in tandem with the endocrine system, so that immediate responses
can be effected by nerves, whilst longer term responses and functions are managed by
hormones. Sensations are also mediated by nerves.
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While the major parts of the brain are interconnected, each can also be subdivided into
a great many areas dependent either on their cellular structure or their function. The
basic layers with which we are concerned here are the central core, the limbic system
and the cerebral cortex.
Parts of the brain: Question
Q8: Complete the labelling of the diagram using the words provided.
5 min
..........................................
1.3.1
The central core
Learning Objective
By the end of this section, you should be able to:
• state that the central core comprises the medulla and the cerebellum;
• state that the medulla regulates breathing rate, heart rate, arousal and sleep;
• state that the cerebellum controls balance, muscular co-ordination, posture and
movement.
The central core, consisting of the medulla and the cerebellum, is an ancient part of
the brain in that it does much the same in humans as it does in other mammals. It
takes care of much of the housekeeping in the body that would be dangerous to leave
a human in charge of. The medulla and the cerebellum are, however, very different in
both structure and function.
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Medulla
The medulla, like the spinal cord, has the grey matter in the centre and the fatty
white matter on the outside. It is a key part of the autonomic nervous system and,
through the sympathetic and parasympathetic neurons, it controls the heart rate set by
the pacemaker, or sino-atrial node (SAN). It also regulates breathing, in response to
impulses from the receptors that detect blood carbon dioxide concentrations, and blood
pressure, in response to the degree of stretch detected by receptors in the artery walls.
Simple reflexes such as coughing, sneezing, swallowing and vomiting are controlled by
the medulla, as are alertness (arousal) and consciousness (sleep).
Cerebellum
The cerebellum, like the cerebrum, has the grey matter on its convoluted outer surface,
while the white matter is contained internally. However, the way in which the neurons
interact is totally different - deep thought is the last thing that is required of the
cerebellum. Although consisting of only about one eighth of the total brain mass, it
contains as many neurons as the whole of the rest of the brain.
It is the cerebrum which initiates movement, but the cerebellum is responsible for
its accurate timing, precision, and co-ordination. This is achieved by matching the
contraction of the antagonistic muscles involved; body posture is controlled in the same
way.
Maintaining balance is another of the cerebellum's responsibilities; think of the range of
sensory information and muscular control that is needed to perform well on a skateboard
and you will begin to understand what a sophisticated computer the cerebellum must be.
The central core: Question
Q9:
Complete the table by putting the processes into their correct column.
Medulla
Cerebellum
Processes: arousal, balance, breathing, movement, muscular coordination, posture,
sleep, heart rate.
..........................................
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TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM
1.3.2
The limbic system
13
Learning Objective
By the end of this section, you should be able to:
• state that the limbic system is concerned with the formation of memories,
influencing emotional and motivational states;
• state that the limbic system contains many parts, one of which is the
hypothalamus which influences the pituitary by means of the secretion of
hormones;
• state that other parts of the limbic system regulate homeostasis by means of
the autonomic nervous system, e.g. blood pressure by contraction/relaxation of
smooth muscle in artery walls;
• state that the limbic system also regulates body temperature by means of the
autonomic nervous system;
• state that the limbic system is also involved in the control of water balance by
the secretion of ADH.
The limbic system forms the inner border of the cerebrum and is not a single entity but
a group of brain structures with quite diverse functions. Two in particular are mentioned
below: the hippocampus and the hypothalamus. Overall, it is involved in the following
areas and exerts its effect by influencing the endocrine system and the autonomic
nervous system.
a) Determines states of emotion and motivation. These are inter-related and actually
quite difficult states of mind to define.
• Emotion - is associated with mood, temperament and personality, e.g. anger,
desire, envy.
• Motivation - determines which behaviour will take place, how strongly it will
be expressed, and for how long.
b) Involved in the formation of long-term memories (in the hippocampus
particularly).
c) Influences the production of hormones by the pituitary gland, by itself releasing
hormones from the hypothalamus which stimulate or inhibit pituitary activity.
d) Homeostatic regulation of:
• body core temperature around the set point of 37 ◦ C, e.g. by causing
vasodilation and vasoconstriction by relaxing and contracting the smooth
muscle in the walls of smaller arteries and arterioles serving the skin, plus
a wide range of other mechanisms;
• blood pressure, by controlling the contraction/relaxation of the smooth muscle
of arterial walls in response to impulses from their stretch receptors;
• water balance, through the production of antidiuretic hormone (ADH) in the
hypothalamus, which is stored and released from the pituitary gland.
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TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM
1.3.3
The cerebral cortex
Learning Objective
By the end of this section, you should be able to:
• state that the cerebral cortex is the centre of conscious thought;
• state that the cerebral cortex receives sensory information, coordinates
voluntary movement, makes decisions, recalls memories and alters behaviour
in the light of experience;
• explain that functions are localised in the cerebral cortex into sensory areas,
motor areas, and association areas;
• state that the association areas deal with thought processes, language,
imagination and intelligence;
• state that the left cerebral hemisphere deals with information from the right
visual field and the right side of the body, and vice versa;
• state that the cerebral hemispheres are connected by the corpus callosum,
which allows transfer of information;
• state that the brain operates as an integrated whole.
The cerebral cortex is the thin outer layer of the cerebrum. Being intensely folded
(convoluted), its large surface area maximises the number of interconnections possible
between neurons. It is 2-4mm thick and consists of grey matter which comprises the
cell bodies of neurons and unmyelinated neurons (which lack a fatty myelin sheath).
The inner layers of the cerebrum consist of white matter which is largely composed of
myelinated axons connecting different parts of the cerebral cortex with each other and
with other parts of the nervous system. This arrangement is the same in the cerebellum,
but is reversed in the medulla and the spinal cord.
Broadly, the cortex can be said to comprise three parts: the sensory, motor, and
association areas. These reflect the evolutionary history of the cerebrum as the part
of the brain which receives incoming information from the sense organs, appraises it,
and sends out signals to the appropriate organs to make a response.
The modern human cerebral cortex is also the centre of conscious thought. Not only
does it receive sensory information, it coordinates voluntary movement (as opposed to
reflexes), makes decisions, recalls memories and uses experience to modify behaviour
(learning).
Sensory areas
The senses of vision, hearing, and touch are served by the visual cortex, auditory cortex
and somatosensory cortex. On each hemisphere, the visual cortex is located at the
back, the somatosensory cortex on either side, just to the rear of the midline, and the
auditory cortex immediately below it. Other senses, such as taste and smell, also have
localised areas which deal with them (and may include other parts of the brain).
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TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM
Motor areas
The motor areas of each hemisphere are also located down the midline, immediately in
front of the somatosensory areas. Both the somatosensory and motor cortices can be
subdivided according to the parts of the body to which they relate, the size of each area
reflecting the sensitivity and degree of fine motor control involved.
Until recently, knowledge of the functions of different parts of the brain was based on
the observed results of brain damage. A wide range of modern techniques, such as
electroencephalographs and brain scans, have allowed much more detailed analysis.
Electroencephalographs
Electroencephalographs (EEGs) show electrical activity in the brain.
Electroencephalographs of brain electrical activity
CAT scans
It is useful to compare patterns of activity using EEGs, especially when comparing
normal and abnormal brainwaves. However, these do not give good evidence of
localisation of function.
A different brain scan called a CAT scan (Computer Assisted Tomography), shows
metabolic activity, providing better evidence for localisation of function. For example,
while listening, metabolic activity in the areas of the brain involved in hearing can be
traced.
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TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM
CAT scans and brain activity
10 min
The areas of brain activity when a subject is performing the following activities are
summarised in the following diagram:
1. hearing;
2. seeing;
3. speaking;
4. areas associated with particular activities.
..........................................
Unfortunately, CAT Scans and Electroencephalographs tell us little on their own.
Observation of people who have suffered brain injuries and subsequent dissection of
their brain tissue after death have provided much more evidence.
It seems that the brain has tissues allocated to receiving information from the senses
(the somatosensory area, or simply the sensory area) and tissues sending instructions
to the muscles (the motor area) localised in adjacent parts of the cortex. The brain, in
fact, allocates the size of each area of sensation and control according to the
importance of the functions carried out. The more sophisticated the senses received,
and the finer the control of the muscles, the more brain tissue is allocated.
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TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM
Localisation of function: Motor and sensory humunculi
A large part of the motor area is devoted to the hands and lips. This allows a fine
degree of motor control. For example, fingers can hold an egg without crushing it or
manoeuvre a coin from finger to finger. Remember that the left motor cortex controls
the right side of the body and vice versa.
..........................................
As shown in the activity above, there is a major organisation of tissues to enable easy
linkage of sensory messages from a specific area of the body with the motor impulses
required to control these organs and tissues. The homunculus is a visual way of
explaining this organisation. The somatosensory area receives information from cold,
heat, pain, touch and kinaesthetic receptors in the skin. Thus, an impulse coming in
from a leg is sensed by neurons in the somatosensory area adjacent to the neurons of
the motor area which direct the movement of that leg.
Large parts of the sensory area are devoted to the lips, fingers and sex organs, making
them very sensitive. This explains why we kiss with the lips and why infants explore
new toys with their lips. Similarly, large parts of the motor area are devoted to the
tongue and lips, allowing speech, and to the fingers, allowing fine manipulation.
The great apes also have fine control of lips and tongue, but, crucially, they lack a voice
box which we have evolved due to different selection pressures operating during our
evolution.
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TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM
Association areas
At the simplest level, the association areas integrate sensory information from different
sensory areas and relate it to past experience. A decision is then made and neuron
impulses sent to the motor areas to give responses.
However, the association areas are also where the individual person resides, as they are
the location of thought processes, personality, imagination, language and intelligence.
These are not easy concepts to define, and fortunately are not part of this syllabus. But
just to whet the appetite, here are some suggestions:
• thought: mental activity of which we are aware and undertake deliberately, that
generates ideas and underlies almost all human actions;
• personality: the sum of an individual's emotions, attitudes and behaviour;
• imagination: helps us to make sense of the world and learn, by allowing us to form
visual or sensory images without actually experiencing them at the same time;
• language: a system of signs, gestures or sounds which convey particular
meanings;
• intelligence: mental ability, either inborn or acquired, to pay attention, remember,
process language, solve problems and make decisions; this is a very controversial
topic.
Association areas for speaking
10 min
How different parts of the association area in the brain respond to written and spoken
words
..........................................
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Left and right hemispheres
The cerebrum is divided into the left and right hemispheres. These are not independent
structures; they are linked by the corpus callosum which allows the transfer of
information between the hemispheres.
Although the hemispheres appear to duplicate many functions, there are important
differences.
A treatment for severe epilepsy involves cutting all or part of the corpus callosum in
order to isolate the two cerebral hemispheres. The subsequent behaviour of such
split-brain patients, in whom the two hemispheres cannot communicate properly, shows
that tasks are not evenly divided between the two hemispheres. Images appear to be
processed by the left hemisphere in most people. Language and analytical skills are also
processed here. The right hemisphere controls visuospatial tasks, such as recognising
facial features and arranging objects or reading maps.
These findings have been corroborated by observation of subjects with trauma to
particular regions of the cerebrum.
Split-brain study
10 min
..........................................
Despite the apparent localisation of function in many areas of the brain, it is also the
case that a great many functions involve the activity not just of different areas of the
cerebral hemispheres, but also the other parts of the brain. The brain in fact operates as
an integrated whole, but one which shows remarkable powers of flexibility in response
to damage, e.g. as a result of a stroke.
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Limbic system and cerebral cortex: Question
Q10: Complete the table by putting words from the list below to correctly match the
statements about the limbic system and the cerebral cortex. Some items may be used
more than once.
Process
Area
Controls voluntary movement
Processes information for the formation of
memories
Transfers information between hemispheres
Influences the secretions of the pituitary
Recalls memories
Deals with language and imagination
Receives impulses from the skin
Centre of conscious thought
Controls the left side of the body
Acts as an integrated whole
Word list: association area, brain, cerebral cortex, corpus callosum, hypothalamus,
limbic system, motor area, right cerebral hemisphere, somatosensory area.
..........................................
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TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM
1.4
Learning points
Summary
Introduction
• The nervous system contains three types of neuron, namely sensory, motor
and interneurons.
• Sensory neurons connect sense receptors with the central nervous system.
• Motor neurons connect the central nervous system to muscles or glands.
• Interneurons may connect with sensory, motor or other interneurons.
• The nervous system analyses sensory information from both the external
and internal environment.
• The body stores some of this information and makes decisions about
appropriate responses and behaviours.
• Motor responses may be made by initiating muscular contractions or
glandular secretions.
Divisions of the nervous system
• The nervous system is divided into the central and peripheral nervous
systems.
• The central nervous system comprises the brain and spinal cord.
• The peripheral nervous system is divided into the somatic and autonomic
nervous systems.
• The autonomic nervous system is further subdivided into the sympathetic
and the parasympathetic nervous systems.
Central and peripheral nervous systems
• The central nervous system consists of the spinal cord and the brain,
including the retinas of the eyes and the optic nerve.
• The peripheral nervous system comprises all sensory and motor neurons
outside of the central nervous system.
• The peripheral nervous system comprises the somatic and autonomic
nervous systems.
• The somatic nervous system controls the voluntary movement of skeletal
muscles.
• This control involves sensory neurons (e.g. connected to stretch receptors
in striped/striated muscle in leg) and motor neurons.
• The autonomic nervous system is responsible for involuntary homeostatic
control of many body functions.
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Summary Continued
• This control also involves sensory neurons (e.g. connected to stretch
receptors in smooth muscle of artery walls) and motor neurons.
• The motor neurons of the autonomic nervous system may connect to
smooth muscle (e.g. in the wall of the gut), cardiac muscle (e.g. pacemaker)
or glands (e.g. adrenal gland).
Autonomic nervous system
• The autonomic nervous system
parasympathetic nervous systems.
• The sympathetic
antagonistically.
and
comprises
parasympathetic
the
sympathetic
nervous
systems
and
act
• The sympathetic nervous system prepares the body for action: 'fight or
flight'.
• The parasympathetic nervous system returns the body to a relaxed, standby
condition: 'rest and digest'.
• The sympathetic nervous system causes increases in heart and breathing
rates, and decreases in peristalsis and intestinal secretions.
• The parasympathetic nervous system causes decreases in heart and
breathing rates, and increases in peristalsis and intestinal secretions.
Parts of the brain
• The brain consists of three major regions:
cerebrum.
medulla, cerebellum and
• The cerebrum comprises two interconnected hemispheres.
The central core
• The central core comprises the medulla and the cerebellum.
• The medulla regulates breathing rate, heart rate, arousal and sleep.
• The cerebellum controls balance, muscular co-ordination, posture and
movement.
The limbic system
• The limbic system is concerned with the formation of memories, influencing
emotional and motivational states.
• The limbic system contains many parts, one of which is the hypothalamus
which influences the pituitary through the secretion of hormones.
• Other parts of the limbic system regulate homeostasis by means of the
autonomic nervous system, e.g. blood pressure by contraction/relaxation
of smooth muscle in artery walls.
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Summary Continued
• The limbic system also regulates body temperature by means of the
autonomic nervous system.
• The limbic system is also involved in the control of water balance by the
secretion of ADH.
The cerebral cortex
• The cerebral cortex is the centre of conscious thought.
• The cerebral cortex receives sensory information, coordinates voluntary
movement, makes decisions, recalls memories and alters behaviour in the
light of experience.
• Functions are localised in the cerebral cortex into sensory areas, motor
areas, and association areas.
• The association areas deal with thought processes, language, imagination
and intelligence.
• The left cerebral hemisphere deals with information from the right visual
field and the right side of the body, and vice versa.
• The cerebral hemispheres are connected by the corpus callosum, which
allows transfer of information.
• The brain operates as an integrated whole.
1.5
Extended response question
The activity which follows presents an extended response question similar to the style
that you will encounter in the examination.
You should have a good understanding of the nervous system before attempting the
question.
You should give your completed answer to your teacher or tutor for marking, or try to
mark it yourself using the suggested marking scheme.
Extended response question: Nervous system
Give an account of the nervous system under the headings:
15 min
A) divisions of the nervous system; (5 marks)
B) homeostatic control. (5 marks)
..........................................
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TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM
1.6
End of topic test
End of Topic 1 test
Q11: Complete the sentences by matching the parts on the left with the parts on the
right. (10 marks)
Types of neuron:
autonomic nervous
system.
Connect sense receptors to CNS:
somatic and autonomic.
Connect CNS to muscles and glands:
brain and spinal cord.
Connect to other neurons of all types:
central and peripheral.
Analysis of information:
sensory, motor,
interneuron.
Muscular contractions and glandular secretions:
sensory neurons.
Divisions of the nervous system:
motor neurons.
Central nervous system comprises:
central nervous system.
Divisions of the peripheral nervous system:
interneurons.
motor responses.
Sympathetic and parasympathetic:
..........................................
Q12: Complete the sentences by matching the parts on the left with the parts on the
right. (8 marks)
Controls the voluntary movement of skeletal muscles:
connect to smooth and
cardiac muscle.
Skeletal muscle control by sensory and motor
neurons is:
sensory and motor
neurons.
Responsible for involuntary homeostatic control:
sympathetic nervous
system.
Involuntary homeostatic control involves:
parasympathetic nervous
system.
Motor neurons of the autonomic nervous system:
autonomic nervous
system.
Action of the sympathetic and parasympathetic
nervous system:
voluntary.
Increases heart rate, decreases intestinal secretions:
somatic nervous system.
Decreases breathing rate, increases peristalsis:
antagonistic.
..........................................
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TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM
The diagram shows the main parts of the brain in vertical section.
Q13: Identify the part labelled X. (1 mark)
..........................................
Q14: Identify the part labelled Z. (1 mark)
..........................................
Q15: To which part of the nervous system does the brain belong? (1 mark)
..........................................
Q16: The part labelled Y is the corpus callosum. What is its function? (1 mark)
..........................................
Q17: Identify the medulla in the diagram. (1 mark)
..........................................
Q18: State two functions regulated by the medulla. (2 marks)
..........................................
Q19: Name the part of the brain responsible for balance. (1 mark)
..........................................
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TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM
The diagram shows the divisions of the nervous system.
Q20: Identify the part labelled A in the diagram. (1 mark)
..........................................
Q21: Identify the part labelled B in the diagram. (1 mark)
..........................................
Q22: Identify the part labelled C in the diagram. (1 mark)
..........................................
Q23: Identify the part labelled D in the diagram. (1 mark)
..........................................
Q24: Identify the part labelled E in the diagram. (1 mark)
..........................................
Q25: Homeostatic control is regulated by which structures within the autonomic nervous
system? (1 mark)
..........................................
Q26: To which structures are impulses sent during the process of homeostatic control?
(2 marks)
..........................................
Q27: State the effect of the parasympathetic nervous system on heart rate. (1 mark)
..........................................
Q28: State the effect of the parasympathetic nervous system on peristalsis. (1 mark)
..........................................
Q29: In which part of the brain is the hypothalamus located? (1 mark)
..........................................
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TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM
Q30: How does the hypothalamus regulate the function of the pituitary? (1 mark)
..........................................
Q31: State two homeostatic mechanisms regulated by the hypothalamus. (2 marks)
..........................................
Q32: Which part of the cerebrum is the centre of conscious thought? (1 mark)
..........................................
Q33: Apart from the association areas, what are the two localised functional areas of
the cerebrum? (1 mark)
..........................................
Q34: State three mental functions that are dealt with by the association areas. (3 marks)
..........................................
..........................................
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TOPIC 1. THE STRUCTURE OF THE NERVOUS SYSTEM
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Topic 2
Perception and memory
Contents
2.1 Perception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1.1 Segregation of objects . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30
31
2.1.2 Perception of distance . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.1.3 Recognition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
34
38
2.2 Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
40
2.2.1 Sensory Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.2 Short-Term Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
41
43
2.2.3 Long-Term Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2.4 Location of memory in the brain . . . . . . . . . . . . . . . . . . . . . .
46
48
2.3 A note about techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.4 Learning points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
50
51
2.5 Extended response question . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.6 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
54
54
Learning Objectives
By the end of this topic, you should be able to:
• define perception as the process by which sensory information is organised,
identified and interpreted by the brain so that we can make sense of it;
• describe how we segregate and recognise objects;
• describe the different methods by which distance is perceived;
• define memory as the storage, retention and retrieval of information;
• describe the nature of sensory, short-term and long-term memory, and their
relationship;
• describe the location of memory in the brain.
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TOPIC 2. PERCEPTION AND MEMORY
2.1
Perception
Learning Objective
By the end of this section, you should be able to:
• state that perception is the process by which the brain analyses and makes
sense of incoming sensory information;
• describe how perception allows us to segregate objects from one another and
from their background;
• describe how perception allows us to judge the distance of objects;
• describe how perception allows us to recognise objects.
We are aware of our surrounding environment as a result of the physical stimulation
of our sense organs. Thus, light is detected by the rods and cones of the retina,
sound waves by the organs of Corti in the cochlea of the ears, kinetic energy by
mechanoreceptors in the skin, and chemicals by chemoreceptors in the nose and
mouth. These energy signals must be converted into nerve impulses before they can be
processed by the nervous system, a process known as transduction.
In each eye we have some 7 million cones and 75-150 million rods connected to the
brain by a million nerve fibres in the optic nerve. If you look out of the window, you
take in the scene with all of its features, including perhaps trees, buildings, cars, people,
grass and birds, but that is not what your retina detects. Its photoreceptors fire off an
impulse in response to the light which they receive. It is the neurons in the retina, optic
nerve and the visual cortex of the cerebrum which create the image we 'see'. Not only
do they create a seamless picture for us from the individual nerve impulses (which are,
of course, no different to any other impulses), but they organise and interpret this 'data'
so that we do not see mere patches of brown, green, black and white, but objects such
as trees, roads, sheep and clouds.
This interpretation process depends on memory and an analysis of context; fluffy white
objects against a green background are likely to be sheep, but against a blue background
they are more likely to be clouds. Sometimes, this process can be tripped up; if you
have ever been given a cup of tea when you were expecting coffee, especially when
engrossed in some other activity, you may have experienced that moment of confusion
when you can almost hear the cogs turning in your brain. Your system first identifies
the liquid as very strange coffee, and then takes a noticeable time before it correctly
recognises it as tea.
It is necessary then to appreciate that what we consciously perceive is the product of
considerable mental processing, and not what is recorded by our sense organs.
Although the syllabus content is limited to the perception process related to vision, it
applies to all the senses. To you, the bass playing on a particular musical track may be
fantastic, but to your neighbour it may just be a loud noise because they do not have the
experience to separate the sound of the different instruments. Have you added too much
cumin to the curry? Unless they know their spices, nobody will notice. The word 'object'
can therefore be used in a general way to refer to the sound of a specific instrument or
a particular flavour.
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2.1.1
Segregation of objects
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Learning Objective
By the end of this section, you should be able to:
• explain that the brain organises sensory information into figures (objects) and
grounds (background) during perception;
• explain that, in order to make sense of our environment, the brain organises
sensory stimuli into coherent patterns during perception.
Figure and ground
All but the simplest of animals use the information from their sense organs to avoid
predators and to find the essentials of life, such as food, mates, shelter, and water. To
do this, they must distinguish the properties of these objects from amongst the mass of
incoming stimuli so there must be a reference memory against which the information can
be matched. Mammals gain much of this information by means of learning, especially
from the parents. Other types of animal, e.g. most fish and insects, never meet their
parents and so most of this information must be inherited genetically rather than passed
on by social contact or learned by trial and error.
In terms of the sense of sight, this process involves trying to identify known shapes
within what we are seeing. This involves identifying the shape against its surrounding
background which involves segregating the figure from the ground. The best known
example of this is Edgar Rubin's vase.
Rubin's figure-ground vase
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If we concentrate on the white area of the diagram so that the boundary from white
to black represents the edge of the object, then we see a white vase against a black
background. However, if the edge is visualised the other way, from black to white, then
we see two faces in silhouette looking at each other in front of a white background. This
is known 'edge-assignment' and is critical to shape perception.
The intention of disruptive camouflage is to make this process more difficult. Examples
of camouflage include:
• the British Multi-terrain Pattern on army combat clothing, in which some of the
colours match the surroundings and so break up the edge of the image of the
wearer;
• the colour patterns of animals such as the Bengal tiger, which has the same effect
against a background of tall grasses during the day and the shadows of a forest at
night.
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Coherent patterns
In the process of interpreting sensory information, the brain seeks to organise it into
coherent patterns or objects. According to one group of psychologists (Gestalt), this
is achieved by six categories of principles, namely Proximity, Similarity, Closure, Good
Continuation, Common Fate, and Good Form. As a knowledge of these principles is not
required by the syllabus, only two are given as examples. It should be noted that these
principles may not apply if other factors are involved.
Proximity principle
Perception tends to group objects that are close together into a single larger set, and
conversely, objects that are far apart into separate sets.
In line (a), the items are evenly spaced and interpreted as a single unit. In line (b), the
uneven spacing causes the items to be grouped as three units. In line (c), four groups
are induced by the uneven spacing.
Closure principle
Although the actual shape of the panda is not complete, the brain organises it into a
single shape by filling in the gaps by closure.
Segregation of objects: Questions
Q1: What is the purpose of disruptive camouflage patterns?
..........................................
Q2: How do the principles of Proximity and Closure contribute to perception?
..........................................
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2.1.2
Perception of distance
Learning Objective
By the end of this section, you should be able to:
• state that distance is judged in the field using visual cues such as relative size,
superimposition and relative height;
• state that binocular disparity is used to judge distance at close range;
• explain that binocular disparity results from the visual field of the left and right
eyes being different, which means seeing objects from a slightly different angle
where it overlaps;
• state that perceptual constancy means that as objects get closer and the viewing
angle changes, they are still perceived to be the same object.
The accurate estimation of distance does not matter to the same extent to all animals.
Prey species, for example hare or roe deer, have no problem gauging the distance to
their plant food as it does not run away. Their principal concern is to have as large a field
of view as possible in order to detect any movement in their surroundings which might
indicate the presence of a predator. Accordingly, their eyes are located on the side of
the head to maximise their visual field.
To a predatory animal, for example a peregrine falcon swooping at 100mph towards a
fleeing pigeon, or a lion leaping at the back of a galloping zebra, it is a matter of life or
death to both the predator and the prey that the former judges the relative position of
the latter accurately. As predators ourselves, we do not close at potentially lethal speed
with our prey, but the accurate judgment of the distance our arrows or spears had to
travel to strike their target, or the distance to a herd of deer or a hungry-looking bear,
certainly would have been of critical importance in the past. The eyes of predators are
therefore located on the front of the face. If, on a wilderness safari, you notice a large
animal contemplating you with a firm, two-eyed stare, it may be thinking about inviting
you to dinner...
In our modern human lives in the West, only recreational hunters and those involved in
conservation have to estimate range accurately to ensure a humane kill. Yet we all have
to judge distances, both short and long, in myriad different contexts in every day life, e.g.
to climb stairs, cross roads, thread needles or dodge snowballs.
We use a considerable battery of mechanisms to do this, a few of which are capable of
giving an accurate measurement, and most of which tell us about the relative position of
objects. The syllabus refers to two of these, namely visual cues and binocular disparity.
We also consider perceptual constancy which involves the brain breaking its own rules
about distance judging.
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2.1.2.1 Visual Clues
We use a wide variety of visual clues to judge distance. Here, we consider three of
them.
Relative size
Objects that possess similar dimensions can appear to have different sizes depending
on their distance from our eyes. This is known as relative size. In the illustration of a
road disappearing towards the horizon, which demonstrates linear perspective, the
smaller telephone poles are interpreted as being further away. In the photograph of
Glen Affric, the pines trees in the foreground, middle ground and in the distance are all
of the same height.
Linear perspective
Glen Affric
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Superimposition
When objects overlap, those which are partially obscured are perceived to be further
away. This is know as superimposition although it is also called interposition.
Relative height in field
In landscape painting and photography, the horizon is often portrayed somewhere
between 1 /3 and 2 /3 of the way up the image. Objects closest to the horizon appear
the furthest away and those nearest to the top and bottom appear as the closest
(relative height in field). In the photos of County Mayo and Glen Muick, the vegetation
at the bottom of the image appears closest, as do the clouds at the top.
County Mayo and Glen Muick
This makes sense in that, if we look down, the ground on which we are standing is the
closest to us, and if we look straight up, the clouds that we see are (usually) the ones
which are closest to us.
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Perception of distance: Question
Q3: Explain how visual clues give the impression of depth in the following image.
Jamaica Inn, Bodmin Moor, Cornwall
..........................................
2.1.2.2 Binocular disparity
'Binocular disparity' means that your two eyes do not have the same view of anything
at which you look.
The distance between the pupils of our eyes is typically 60-65mm. Therefore, each
eye views the world from a slightly different position, the effect of which is most marked
with objects close to us. If you hold your right hand up vertically in front of your face
with your thumb touching your nose and shut each eye in turn, you will appreciate this
to maximum effect. Your left eye sees your palm and your right eye sees the back of
your hand. If you then move your hand slowly away from your face, closing your eyes
alternately and comparing each view with what you see with both eyes open, very quickly
you will discover that with both eyes open you 'see' only one image, although the view
from each eye is noticeably different. Your visual cortex is merging the two-dimensional
images from each eye into a single, coherent three-dimensional picture. However, this
only applies around the point of focus of the eyes. If you hold your index fingers in front
of your face about 30cm apart and focus on one of your fingers, the other will appear
twice.
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Although with both eyes open we have a total visual field of about 200 ◦ , the portion of
this which is common to both eyes is only about 120 ◦ . As a result of the varying density
of distribution of rods and cones across the retina, over most of this area our vision
is not nearly as precise as it is in the centre, in the area on which we are focussed.
Consequently, our judgement of distance is also most accurate for objects on which we
are focussing.
Binocular disparity is important for judging distance at ranges of up to about 10m;
beyond that, the views from each of the eyes are not sufficiently different.
2.1.2.3 Perceptual constancy
We tend to perceive familiar objects as having a standard shape, size, colour and even
location, despite wide variations in the conditions under which we are observing them.
Thus, you would recognise that the little yellow dog on the other side of the field as a
Labrador and your perception would not change as the dog runs over towards you. In
fact, as it runs, it changes shape; as it passes under a tree, it changes colour (because
of the green light filtering through the leaves); and as it gets closer, it forms a much
larger image. Even if you were looking down on the scene from an upstairs window, with
a very different viewing angle, you would not be confused.
The value of perceptual constancy is that it allows us to recognise familiar objects under
a wide variety of conditions. This effect is reduced if exposure to the object has been
limited (e.g. you have never seen a Labrador before) or if the associated clues to its
identity are reduced (e.g. its colour has changed as a result of 'bog-snorkelling').
2.1.3
Recognition
Learning Objective
By the end of this section, you should be able to:
• state that shape is more important than detail in the recognition of objects;
• explain that we match observed shapes to shape descriptions stored in memory
during perception;
• explain that inference is used to match incomplete information against
memorised shape descriptions during perception;
• explain that the perception of a stimulus or object is influenced by a perceptual
set of past experience, context and expectation.
Every time we see a familiar object, be it a person, tree, beach, or street, the image
created on the retina is different, and yet we discern from that image that the object is
not only similar to one that we have seen before, but actually that it is the same one.
This process is complex, involving several different areas of the brain, yet it also takes
place in any animal that is capable of recognition, e.g. an adult butterfly can identify the
correct food plant for its caterpillar larvae from all of the species growing in a hedgerow.
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The role of shape in recognition
Processing of the visual image takes place in a series of increasingly complex steps
which are located in different areas of the cerebrum. At the simplest level, lines, colour
and orientation are distinguished. Boundaries and contours are filled in next, allowing
figure-ground segregation. Finally, all of the information is combined into the final
object. During this process, no new information is formed, but the existing data is reorganised to emphasise the most detailed information about the object. Overall, it is
shape rather than particular detail which is most important in recognition.
Stored memories
The highest level of processing in perception involves identifying an object by matching it
with a stored memory of that object. Once identified, the object can be assigned various
attributes, such as potential uses, whether we like it or not, or whether it constitutes a
threat to us. These properties have been linked with this object as a result of our past
experience of it.
The role of inference
The information provided by our sense organs is often incomplete, but our brain must
still try to make sense of it. This it does by making assumptions, e.g. about where
boundaries are, which leads to drawing conclusions, e.g. about what the rest of a
partially concealed object will be.
The influence of perceptual set
Given the extent to which assumptions and inferences are involved in perception,
we should not be surprised that the way in which we perceive objects is likely to
quite subjective, and dependent on our previous experience, the context in which we
encounter the stimulus, and what our expectations are. An obvious example would be
the reaction of opposing sets of supporters to a controversial refereeing decision in a
football match. Depending on past encounters with the other team, the reputations of the
referee and the players, the state of the game, and the position on the pitch, supporters
of each side are quite capable of genuinely perceiving the incident in very different ways.
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2.2
Memory
Learning Objective
By the end of this section, you should be able to:
• state that memory is the process of storage, retention and retrieval of
information;
• state that the information stored in memory includes past experiences,
knowledge and thoughts;
• explain that all information entering the brain passes first through Sensory
Memory and then enters Short-Term Memory;
• explain that information in Short-Term Memory is either passed into Long-Term
Memory or is discarded.
In the preceding section about recognition, reference was made to descriptions of
objects being stored in memory. To be able to confirm that we have seen,smelt or
heard something before, we must have been able to convert our initial perception into
a form that can be stored and later retrieved so that we can compare it with our new
percept. By the same token, any animal which can change its behaviour in the light of
experience, i.e. learn, must also be able to carry out this information storage, retention
and retrieval process. The information which we can store takes all forms; not only are
images, smells, tastes, textures, and sounds stored, but also our feelings about events
and the details of complex information such as equations or poems. Even our thoughts
are remembered, although these do not pass through the sense organs.
There are different stages in the process of memory. All incoming sensory information
is put into Sensory Memory before some of it is passed almost immediately to
Short-Term Memory (STM). As the name implies, information only remains in
Short-Term Memory for a brief period and is then either discarded or passed into
Long-Term Memory (LTM).
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2.2.1
Sensory Memory
41
Learning Objective
By the end of this section, you should be able to:
• state that Sensory Memory retains all input from the sense organs;
• state that information is retained in Sensory Memory for a few seconds.
Each of our sense organs continuously feeds impulses into the region of the cerebrum
which relates to that particular sense. Each form of sensory information is processed
separately:
• auditory - echoic memory - processed in the temporal lobe;
• visual - iconic memory - processed in the occipital lobe;
• tactile - haptic memory - processed in the postcentral gyrus of the parietal lobe.
The classic demonstration of visual Sensory Memory (iconic memory) is the drawing of
shapes with a sparkler on a dark night. As the light moves, we briefly 'see' the shape of
its track through the air.
The information in Sensory Memory is raw data, uninterpreted, and mostly of no
relevance to us. Of this vast quantity of information, only a few items pass into ShortTerm Memory; the rest is discarded after 1 /5 to 1 /2 second. Which information is so
transferred is determined by subconscious filtering through the mental process known
as attention. This causes selective concentration on one aspect of the environment to
the exclusion of all others. This is why you shouldn't speak into a mobile phone while
driving, or worse, send a text message!
Transfer into Short-Term Memory takes place in the hippocampus, where the
information from the various sensory areas of the cerebrum is assimilated into a single
experience.
The position of the hippocampus
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TOPIC 2. PERCEPTION AND MEMORY
Location of Sensory Memory: Question
Q4: Complete the diagram to show the location of the different types of Sensory
Memory.
..........................................
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2.2.2
Short-Term Memory
43
Learning Objective
By the end of this section, you should be able to:
• state that the memory span of Short-Term Memory (STM) is the number of items
that can be stored;
• state that the average memory span for digits is 7 (usual range 5-9);
• state that information may be retained in STM by rehearsal;
• state that information is lost from STM by displacement or decay;
• explain the serial position effect: items at the start of a list are recalled because
they have been rehearsed and passed to LTM; items at the end of a list are
recalled because they are still in STM; items in the middle of the list are not
recalled as they have been displaced from STM by later items and have not
been transferred to LTM;
• state that the memory span of STM can be increased by chunking;
• explain that chunking is the grouping of separate items of information so that
they pass into the memory as a single unit;
• state that Working Memory is an extension of STM;
• state that Working Memory is used to perform cognitive tasks (e.g. reasoning,
comprehension).
We often think of Short-Term Memory as information newly-received from the senses,
but it may include information recently retrieved from Long-Term Memory or recent
mental processing. We can call this extended form of Short-Term Memory 'Working
Memory'. Short-Term Memory has a limited facility to store information which is known
as the memory span. It makes sense that it is not cluttered with too much information.
"The Curious Incident of the Dog in the Night-time" by Mark Haddon is an insightful
fictional account of how an autistic boy has difficulty with an excess of information.
Current processing of information, or Short-Term Memory, has a capacity of seven
items, plus or minus two, for most people. Practice can improve this. For example,
'chunking' items to convert several pieces of information into one can increase this
capacity greatly. If you were given fifteen random letters to memorise, you could chunk
them in groups of three to make five nonsense words to remember. Phone numbers
are often recalled in chunks, the area code as one chunk and the rest put into little
groups depending on associations.
Short-Term Memory lasts only 15-30 seconds unless rehearsal or repetition is involved.
Rehearsal often involves repeating information, such as a telephone number, until it is
dialled, although speed-dialling and mobile phone contact lists have reduced the
practice of recalling numbers. Distractions greatly reduce this facility. This repetition is
referred to as acoustic coding and repetition may be aloud or 'in-your-head'.
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Given that memories only last for a few seconds normally, and that only around seven
items are remembered at any one time, Short-Term Memory decays, or is displaced,
rapidly.
Serial Position Effect
Storage of memory is greatly enhanced by rehearsal. You may become fed up with
your parents repeatedly recalling the good old days, but this is simply a way to keep
memories alive.
One way to demonstrate memory storage is to investigate the serial position effect.
Serial position effect 1
15 min
Collect at least twenty varied items. Present them briefly, one at a time, in a
predetermined sequence, to a friend. Hide them when they are not being shown.
Ask your friend to recall the items, using any descriptions, in any order.
Where did she do best? With the earlier items (the primacy effect) or the last (the
recency effect)?
..........................................
Even if assuming that someone was paying attention, twenty items are too many to recall
from Short-Term Memory. The subject initially tries to store the information in Long-Term
Memory by rehearsal, using mnemonics, or some other trick, such as associating the
items with a previously learned list.
Most people can only encode seven items in the Short-Term Memory and do not have
enough time to rehearse or repeat all of the items. Thus, the first few items might
have been stored in the Long-Term Memory and the last few remain in the Short-Term
Memory, but storage and, consequently, retrieval of the items mid-list will be haphazard.
Serial position effect 2
Look at the tables of data and then answer the questions which follow.
10 min
Twenty items were shown briefly to a fourth year student. The table below shows which
items were recalled. For example, the student recalled item 5, but not item 6.
Item
Number
Recalled?
Item
Number
Recalled?
1
2
3
4
5
√
√
√
√
√
11
12
13
14
15
6
8
9
10
√
16
√
Items shown to the student:
7
√
17
18
19
20
√
√
√
√
= item recalled
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Q5: Using your understanding of the serial position effect, explain the results.
..........................................
Q6: What is unusual about the Short-Term Memory of the subject?
..........................................
Q7: Sometimes an item is recalled regardless of its position. Why might his occur?
..........................................
Working Memory
The concepts of 'Short-Term Memory' and 'Working Memory' have been the subject of
much research since the development of a classical model of memory in the 1960s.
A simple interpretation is that while information is passed into Short-Term Memory
for storage (for a short period), the manipulation or organisation of this information
is carried out in Working Memory by means of the processes of reasoning and
comprehension.
Short-Term Memory: Questions
Q8: Complete the sentences by matching the parts on the left with the parts on the
right.
Memory span of STM is:
STM.
Items remain in STM for:
cognitive tasks.
Items are maintained in STM by:
displacement and decay.
Items are lost from STM by:
15-30 seconds.
STM memory span can be increased by:
7 (5-9) items.
Working Memory is an extension of:
rehearsal.
chunking.
Working Memory is used to perform:
..........................................
Q9: When shown a list of twenty items, people can recall a few items from the start of
the list and a few from the end, but not those in the middle.
i
Explain why the early numbers are recalled.
ii
Explain why the later numbers are recalled.
iii Explain why the middle numbers are not recalled.
..........................................
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2.2.3
Long-Term Memory
Learning Objective
By the end of this topic, you should be able to:
• state that encoding is the process by which information is converted into a form
which can be passed from STM to LTM;
• state that LTM can store unlimited information indefinitely;
• state that information can be transferred from STM to LTM by rehearsal,
organisation or elaboration of meaning;
• state that rehearsal involves repetition of the information to be memorised;
• state that organisation involves grouping the information with other similar items;
• state that elaboration involves linking the information with emotions, images and
other memories;
• state that repetition produces shallow encoding of information;
• state that organisation of information into groups with similar properties
produces relational encoding of information;
• state that elaboration by linking with previous memories produces elaborative
encoding of information;
• state that relational and elaborative encoding are more permanent than shallow
encoding;
• state that retrieval is the recall from LTM to the Working Memory of STM;
• state that retrieval is aided by the use of contextual clues which relate to the
conditions under which the memory was formed.
The process of converting information in the form of impulses that enters Sensory
Memory into a form which can be stored is known as encoding. Transfer from Sensory
Memory to Short-Term Memory is controlled by the mental process of attention over
which we have no conscious influence.
Transfer from STM to LTM
Transfer from STM to LTM can be achieved by three methods:
1. rehearsal (shallow encoding), which is repeating the information many times when applied to a list of random words, this repetition is a very inefficient method of
transferring such information to LTM; however, as anyone who plays an instrument
or any sport will know, frequent repetition is essential to the perfection of motor
skills, whether it be playing arpeggios in the scale of A minor or escaping from
bunkers;
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2. organisation (relational encoding) - by grouping an item of information with other
items of similar type is a form of deep encoding which links the new item with
others already in memory; the creation of mind maps or key-word diagrams of
information to be memorised for exams is a prime example of organisation, in
which individual items are located within a logical framework;
3. elaboration (elaborative encoding) - by linking information to existing memories,
or to other information such as emotions, scents, tastes or textures, memories can
be created by another form of deep encoding; thus, if a person's name can be
linked to their interesting choice of shoes/hairstyle/perfume, or the place where
you met, it is much more likely to be transferred into LTM.
Retrieval
For us to become conscious of items stored in memory, they must be recalled from LTM
to STM. This process is greatly aided by information which is linked to the conditions,
or context, under which the information was encoded. The reverse of this is also true.
You might only have ever seen the person who drives the school bus in that situation so
when you meet her in the supermarket you find it difficult to place her because some of
the key contextual clues are missing, e.g. the uniform and the bus. In the same way, the
taste of an ice-cream might remind you of a childhood day by the beach.
Long-Term Memory: Question
Q10: Complete the sentences by matching the parts on the left with the parts on the
right.
Process by which information is converted to a form
which can stored in memory:
organisation.
Transfer from STM to LTM by repetition:
retrieval.
Transfer from STM to LTM by grouping with similar
items:
rehearsal.
Transfer from STM to LTM by linking with existing
memories:
contextual.
Encoding produced by repetition:
elaboration.
Encoding produced by linking with emotions:
encoding.
Recall from LTM to STM:
elaborative.
Clues which aid recall:
shallow.
..........................................
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2.2.4
Location of memory in the brain
Learning Objective
By the end of this topic, you should be able to:
• state that LTM can be sub-divided according to the type of information stored;
• state that episodic memory stores events and experiences;
• state that semantic memory stores facts and concepts;
• state that procedural memory stores skills: both motor and cognitive;
• state that emotional memory stores emotional responses to past events;
• state that spatial memory stores information about the location of physical
objects in space;
• state that the different types of memory are located in different parts of the
cerebrum;
• state that episodic and semantic memory are located in the region of the
cerebral cortex where the sensory information was first encoded;
• state that procedural memories are linked to long-term changes in the motor
cortex;
• state that emotional memories involve links between the cortex and the limbic
system;
• state that spatial memory is located in the hippocampus of the limbic system.
Location of memory
The information which is stored in Long-Term Memory is located in different parts of the
cerebrum depending on the type of information. The types of memory, the information
stored and the location are summarised in the following table.
Type of
memory
Information stored
Location in cerebrum
Episodic
Events and experiences
Area of cerebral cortex where
sensory information is first encoded
Semantic
Facts and concepts
Area of cerebral cortex where
sensory information is first encoded
Procedural
Motor and cognitive skills
Motor cortex
Emotional
Emotional responses
Amygdala of the cortex and the
limbic system
Spatial
Location of a physical object
in space
Hippocampus of the limbic system
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Types of memory
The main types of memory are:
• episodic - the memory of events in our lives, including places, times, dates, how
we felt about it, and other people involved;
• semantic - the memory of the meaning of words, facts and concepts, but does not
concern specific events or experiences;
• declarative - episodic and semantic memory together make up one of the two
main types of memory, namely declarative memory. They involve memories, such
as facts and dates, that can be consciously recalled;
• procedural - the memory of how to carry out tasks, both mental and physical. This
covers a broad range of complex sets of procedures from putting on your socks to
solving equations and reading. Key points are that these skills can be carried out
without conscious thought, so do not involve the STM, and that the memories are
acquired as a result of frequent repetition.
There are two other forms of memory:
• spatial (or topographic) - the memory of the organisation of our environment and
how we are positioned within it - we store a cognitive map of our world, which
allows us to navigate; this consists of the general layout of places and key locations
within them;
• emotional - the memory of intense emotional responses, which are usually linked
with specific events, but may be stored separately - agood example is the feeling
of fear; we all know what it feels like to be afraid, but it is very helpful to our survival
that we should also remember situations which have made us afraid.
Location of memory in the brain: Questions
Q11: Complete the table with the types of memory from the list.
Type of memory
Information stored
Events and experiences
Facts and concepts
Motor and cognitive skills
Emotional responses
Location of physical objects in space
Types of memory: episodic, emotional, procedural, semantic, spatial.
© H ERIOT-WATT U NIVERSITY
50
TOPIC 2. PERCEPTION AND MEMORY
..........................................
Q12: Complete the sentences by matching the parts on the left with the parts on the
right.
Events and experiences; Facts
and concepts:
located in the motor cortex.
Motor and cognitive skills:
located in the hippocampus of the limbic
system.
Emotional responses:
area of cerebral cortex where sensory
information first encoded.
Location of physical objects in
located in the amygdala of the cortex and the
space:
limbic system.
..........................................
2.3
A note about techniques
Early research on human brain function was based on observing the effect of accidental
damage to particular parts of the brain and the accompanying changes in behaviour
and mental abilities. In the mid-20 th century, this was amplified by the study of
laboratory animals (particularly rats and monkeys) in which the brain had been
deliberately damaged. Later, this rather coarse approach was superceded by the
surgical implantation of micro-electrodes into the brain which allowed stimulation of very
specific areas and the observation of the associated behavioural effects.
In the later part of the 20 th century, the development of two techniques in particular
revolutionised our understanding of human brain activity:
• magnetic resonance imaging (MRI) - uses powerful electro-magnets to align some
atomic nuclei in the body (especially those of hydrogen atoms in water), and then
radio frequency fields to alter the direction of this alignment. The effect is to induce
rotating magnetic fields which can be detected by a scanner. In the study of brain
activity, Functional MRI (fMRI) is used to give an indication of changing blood flow
to different parts of the brain, and hence relative levels of neural activity. As it uses
magnetic fields and radio signals to detect activity, and not radioactive emissions,
MRI carries much less risk than PET;
• positron emission tomography (PET) - this is a form of nuclear imaging which
detects radiation emitted from biologically active molecules which have been
labelled with isotopes which typically have a half-life of 15mins or less (so after
an hour, only 6% is left). In the study of brain function, the most frequently
used molecule is a form of glucose labelled with fluorine-18. Scanners detect the
emitted radiation and high levels of emission indicate a high level of respiration,
and so an area of the brain which is very active. Because of the risks associated
with exposure to ionising radiation, PET is mainly restricted to the detection of
cancers. To maximise the acquisition of information, PET scans are now usually
combined with MRI scans.
© H ERIOT-WATT U NIVERSITY
TOPIC 2. PERCEPTION AND MEMORY
2.4
Learning points
Summary
Perception
• Perception is the process by which the brain analyses and makes sense of
incoming sensory information.
• Perception allows us to segregate objects from one another and from their
background.
• Perception allows us to judge the distance of objects.
• Perception allows us to recognise objects.
Segregation
• The brain organises sensory information into figures (objects) and grounds
(background) during perception.
• In order to make sense of our environment, the brain organises sensory
stimuli into coherent patterns during perception.
Perception of distance
• Distance is judged in the field, using visual clues such as relative size,
superimposition, and relative height.
• Binocular disparity is used to judge distance at close range.
• Binocular disparity results from the visual field of the left and right eyes
being different and, where it overlaps, seeing objects from a slightly different
angle.
• Perceptual constancy means that as objects get closer and the viewing
angle changes, they are still perceived to be the same object.
Recognition
• Shape is more important than detail in the recognition of objects.
• We match observed shapes to shape descriptions stored in memory during
perception.
• Inference is used to match incomplete information against memorised
shape descriptions during perception.
• The perception of a stimulus or object is influenced by a perceptual set of
past experience, context and expectation.
Memory
• Memory is the process of storage, retention and retrieval of information.
• The information stored in memory includes past experiences, knowledge
and thoughts.
© H ERIOT-WATT U NIVERSITY
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52
TOPIC 2. PERCEPTION AND MEMORY
Summary Continued
• All information entering the brain passes first through Sensory Memory and
then enters Short-Term Memory.
• Information in Short-Term Memory is either passed into Long-Term Memory
or is discarded.
Sensory Memory
• Sensory Memory retains all input from the sense organs.
• Information is retained in Sensory Memory for a few seconds.
Short-Term Memory
• The memory span of Short-Term Memory (STM) is the number of items that
can be stored.
• The average memory span for digits is 7 (usual range 5-9).
• Information may be retained in STM by rehearsal.
• Information is lost from STM by displacement or decay.
• The serial position effect is explained as follows:
– items at the start of a list are recalled because they have been
rehearsed and passed to LTM;
– items at the end of a list are recalled because they are still in STM;
– items in the middle of the list are not recalled as they have been
displaced from STM by later items and have not been transferred to
LTM.
• Memory span of STM can be increased by chunking.
• Chunking is the grouping of separate items of information so they pass into
memory as a single unit.
• Working Memory is an extension of STM.
• Working Memory is used to perform cognitive tasks (e.g.
comprehension).
reasoning,
Long-Term memory
• Encoding is the process by which information is converted into a form which
can be passed from STM to LTM.
• LTM can store unlimited information indefinitely.
• Information can be transferred from STM to LTM by rehearsal, organisation
or elaboration of meaning.
• Rehearsal involves repetition of the information to be memorised.
© H ERIOT-WATT U NIVERSITY
TOPIC 2. PERCEPTION AND MEMORY
Summary Continued
• Organisation involves grouping the information with other similar items.
• Elaboration involves linking the information with emotions, images and other
memories.
• Repetition produces shallow encoding of information.
• Organisation of information into groups with similar properties produces
relational encoding of information.
• Elaboration by linking with previous memories produces elaborative
encoding of information.
• Relational and elaborative encoding are more permanent than shallow
encoding.
• Retrieval is the recall from LTM to the Working Memory of STM.
• Retrieval is aided by the use of contextual cues which relate to the
conditions under which the memory was formed.
Location of memory
• LTM can be sub-divided according to the type of information stored.
• Episodic memory stores events and experiences.
• Semantic memory stores facts and concepts.
• Procedural memory stores skills, both motor and cognitive.
• Emotional memory stores emotional responses to past events.
• Spatial memory stores information about the location of physical objects in
space.
• The different types of memory are located in different parts of the cerebrum.
• Episodic and semantic memory are located in the region of the cerebral
cortex where the sensory information was first encoded.
• Procedural memories are linked to long-term changes in the motor cortex.
• Emotional memories involve links between the cortex and the limbic system.
• Spatial memory is located in the hippocampus of the limbic system.
© H ERIOT-WATT U NIVERSITY
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54
TOPIC 2. PERCEPTION AND MEMORY
2.5
Extended response question
The activity which follows presents an extended response question similar to the style
that you will encounter in the examination.
You should have a good understanding of Short-Term Memory before attempting the
question.
You should give your completed answer to your teacher or tutor for marking, or try to
mark it yourself using the suggested marking scheme.
Extended response question: Short-Term Memory
Give an account of Short-Term Memory under the headings:
15 min
A) increasing memory span; (3 marks)
B) serial position effect; (5 marks)
C) transfer from STM to LTM. (2 marks)
..........................................
2.6
End of topic test
End of Topic 2 test
Q13: Complete the paragraphs by selecting the correct words from the list, some of
which may be used more than once. (14 marks)
In the field, distance is judged by visual
height.
and
Relative
is used in
such as relative
refers to the apparent
of similar objects,
, and
height refers to
in the image.
At close range, binocular
viewpoint.
,
,
of objects
is also used. This uses the fact that each eye has a
We perceive familiar objects in the same way despite changing circumstances, such as
, because of perceptual
.
viewing
Word list: angle, constancy, clues, different, dimensions, disparity, overlap, position,
relative, size, superimposition.
© H ERIOT-WATT U NIVERSITY
TOPIC 2. PERCEPTION AND MEMORY
55
..........................................
Q14: Complete the sentences by matching the parts on the left with the parts on the
right. (8 marks)
Conversion of information into a form that can be passed into LTM:
contextual.
Repetition of information:
retrieval.
Grouping of items of information which are similar:
shallow.
Linking information with emotions and images:
organisation
and
elaboration.
Type of encoding produced by repetition:
rehearsal.
Forms more permanent memories than shallow encoding:
encoding.
Recall from LTM to Working Memory:
elaboration.
Cues which relate to the conditions under which a memory was
formed:
..........................................
organisation.
Q15: Complete the sentences by matching the parts on the left with the parts on the
right. (10 marks)
Memory of events and experiences:
procedural.
Memory of facts and concepts:
emotional.
Memory of motor and cognitive skills:
cerebrum.
Memory of how we felt about past events:
sensory regions of
cortex.
Memory of the location of objects:
cortex and limbic
system.
Part of the brain where all memory is located:
spatial.
Memories of events and facts are stored:
hippocampus.
Skills memories linked to long-term changes:
episodic.
Our feelings about past events involve links between them:
motor cortex.
Part of the limbic system:
semantic.
..........................................
© H ERIOT-WATT U NIVERSITY
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TOPIC 2. PERCEPTION AND MEMORY
Enter a word to complete each of the definitions.
Q16: The analysis and interpretation of sensory information is called (1 mark)
..........................................
Q17: The brain organises sensory information into objects called (1 mark)
..........................................
Q18: The background to these objects is called the (1 mark)
..........................................
Q19: The type of patterns of sensory information organised by the brain is (1 mark)
..........................................
Q20: The organisation of sensory information into object and background is called (1
mark)
..........................................
Select the correct words to match the statements.
Q21: Most important in the recognition of objects: (1 mark)
a) colour
b) shape
c) size
..........................................
Q22: Matching descriptions stored in memory: (1 mark)
a) expectation
b) perception
c) recognition
..........................................
Q23: Matching incomplete information against descriptions in memory: (1 mark)
a) expectation
b) experience
c) inference
..........................................
Q24: Not part of a perceptual set: (1 mark)
a) context
b) expectation
c) inference
..........................................
© H ERIOT-WATT U NIVERSITY
TOPIC 2. PERCEPTION AND MEMORY
Q25: What is meant by the term 'memory'? (1 mark)
..........................................
Q26: Through which aspect of memory does all information entering the brain first
pass? (1 mark)
..........................................
Q27: Which type of memory holds information for a few seconds but retains all visual
or auditory input? (1 mark)
..........................................
Q28: The number of items held in Working Memory is called the (1 mark)
..........................................
Q29: Information is retained in Short-Term Memory by the process of (1 mark)
..........................................
Q30: The process by which the storage of new memories causes the loss of other
memories is called (1 mark)
..........................................
Q31: Without repetition, information is lost from memory by the process of (1 mark)
..........................................
Q32: Short-Term Memory can be improved using the technique of (1 mark)
..........................................
Q33: Cognitive tasks involving information in Short-Term Memory are performed by the
(1 mark)
..........................................
Q34: Complete the sentences by matching the parts on the left with the parts on the
right.
..........................................
..........................................
© H ERIOT-WATT U NIVERSITY
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58
TOPIC 2. PERCEPTION AND MEMORY
© H ERIOT-WATT U NIVERSITY
59
Topic 3
Neurons, neurotransmitters and
neural pathways
Contents
3.1 Neurons . . . . . . . . . . . . . . . . . . . .
3.1.1 Introduction . . . . . . . . . . . . . .
3.1.2 Structure of neurons . . . . . . . . .
3.1.3 Function of the cell body . . . . . . .
3.1.4 Function of dendrites . . . . . . . .
3.1.5 Function of axons . . . . . . . . . .
3.2 Glial cells and myelination . . . . . . . . . .
3.2.1 Glial cells . . . . . . . . . . . . . . .
3.2.2 Myelination . . . . . . . . . . . . . .
3.3 Neurotransmitters . . . . . . . . . . . . . .
3.3.1 Chemical transmission at synapses
3.3.2 Neurotransmitters . . . . . . . . . .
3.3.3 Neurotransmitter threshold . . . . .
3.3.4 Removal of neurotransmitters . . . .
3.3.5 Excitatory and inhibitory transmitters
3.4 Neural pathways . . . . . . . . . . . . . . .
3.4.1 A converging pathway . . . . . . . .
3.4.2 A diverging pathway . . . . . . . . .
3.4.3 A reverberating pathway . . . . . . .
3.4.4 Plasticity of response . . . . . . . .
3.5 Learning points . . . . . . . . . . . . . . . .
3.6 Extended response question . . . . . . . .
3.7 End of topic test . . . . . . . . . . . . . . .
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60
60
61
65
66
67
69
69
70
72
73
74
74
74
76
77
79
79
79
80
83
85
86
Learning Objectives
By the end of this topic, you should be able to:
• describe the structure and function of the cells of the nervous system;
• explain the way in which information is passed on in the nervous system;
• describe the ways in which neurons are linked together in pathways and explain
the effect of such groupings.
60
TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS
3.1
Neurons
Nerve tissue comprises neurons, which transmit nerve impulses, and glial cells, which
provide support for neurons. This first section considers neurons.
3.1.1
Introduction
Any multi-cellular organism requires some method of passing information between cells
to enable coordinated activity to take place.
Cells mainly communicate with one another by means of chemicals, which travel
between them in a liquid medium. When this involves the secretion of the messenger
chemical into a blood stream, this is known as the endocrine system and the chemicals
are hormones. If carried in a double circulation system, such as that of a mammal or
a bird, this will deliver the chemical to all parts of the body in a matter of seconds. In a
higher plant, such as an oak tree, things take a little longer. Although efficient, endocrine
communication is not suited to dealing with a sudden emergency.
All cells have a very small electrical potential difference across the cell membrane.
Neurons create a temporary reversal of this potential difference to send a signal along
the cell (which can be very elongated) at between 1 and 100 m.s -1 . The junction between
neurons is called a synapse, at the centre of which is a gap called the synaptic cleft.
By reducing the distance between adjacent neurons to 20-40nm, the diffusion of the
chemical carrying the message between cells also takes place very quickly. Neurons
thus provide the fast transfer of information around the body that enables complex
animals to behave in the amazingly diverse and sophisticated ways that we observe.
© H ERIOT-WATT U NIVERSITY
TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS
3.1.2
Structure of neurons
61
Learning Objective
By the end of this section, you should be able to:
• describe that the nervous system consists of a range of different cells called
neurons;
• explain that neurons are grouped together to form the brain and spinal
cord of the central nervous system (CNS), and the nerves of the
peripheral nervous system;
• state that neurons receive and transmit impulses (a form of electrical signal);
• state that there are three main types of neuron:
motor neurons and interneurons;
sensory neurons,
• state that sensory neurons carry impulses into the CNS from sense organs;
• state that motor neurons carry impulses out from the CNS to effectors such as
muscles and glands;
• state that interneurons are found in the CNS where they connect with other
neurons;
• describe a neuron as consisting of a cell body with protruding fibres in the form
of one axon and many dendrites.
Neurons are the specialised cells which carry nervous impulses around the body,
allowing the senses to communicate with the brain and the brain to coordinate
responses. The human nervous system (NS) comprises some 10 12 of these cells which
are typically only a few micrometres in diameter.
There are many different types of neuron, of which we study three here:
• sensory neurons, which carry impulses into the Central Nervous System (CNS)
from sense organs;
• motor neurons, which carry impulses out from the CNS to effectors such as
muscles and glands;
• interneurons (also called relay or association neurons), which exist in many forms
and are found in the CNS where they connect with other neurons.
These neurons are grouped together to form the brain and spinal cord of the CNS, and
the nerves of the Peripheral Nervous System.
Each neuron consists of a cell body, much like the typical animal cell in structure, with
an axon extending from the cytoplasm. These can be up to a metre long in humans
although they are often much shorter; in the CNS they are very short. The axon is
wrapped in a sheath of lipoprotein called myelin. Impulses begin in the dendrites,
which are projections from the axon in sensory neurons, and from the cell body of motor
neurons. The impulses then travel towards the cell body and on to the axon terminals at
the end of the axon.
© H ERIOT-WATT U NIVERSITY
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TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS
The cell bodies of sensory neurons are located within the vertebrae, which surround
and protect the spinal cord. In motor neurons the cell body lies within the central grey
matter of the spinal cord, surrounded by the outer white matter, which is composed of
axons with their fatty myelin sheaths. The grey matter of the brain similarly consists
mainly of cell bodies and dendrites, whilst the white matter consists of axons.
The diagram shows how these cells are organised in a simple reflex.
A simple reflex
Neurons themselves are specialised according to function. To achieve this, they require
slight adaptations in structure.
Look at the different structures of sensory, motor and inter-neurons.
Sensory neurons are adapted to take messages from sensory receptors in the skin
and the specialised sense organs (the nose, tongue and ears) to the brain.
Sensory neuron
Note that the cell body sits part way along the axon and that there are no dendrites on
the cell body.
© H ERIOT-WATT U NIVERSITY
TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS
Motor neurons have many dendrites protruding from the cell body, which is end-on to
the axon.
Motor neuron
If a motor neuron that links the spinal cord with the foot was enlarged until the cell
body was the size of a tennis ball, its dendrites would fill your living room and the axon
would be 1.6km long, yet only 13mm in diameter. Axons vary between 0.2 and 300μm
(1 micrometre ≡ 1μm ≡ 1 x 10-6 m) in length. A human axon is typically 50μm in
diameter, excluding the myelin sheath. In a large mammal, a single motor neuron that
links the spinal cord with a digit might be 2 metres long, though the synapses between
one neuron and its neighbour are around 200 x 10 -9 metres in size.
Interneurons typically have a large number of dendrites and a very short axon, although
they have a wide variety of different structures based on this basic pattern.
Interneuron
Note that the axon is very short and lacks myelination.
© H ERIOT-WATT U NIVERSITY
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64
TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS
Structure of neurons: Question
Q1:
Complete the diagram using the labels provided.
15 min
..........................................
© H ERIOT-WATT U NIVERSITY
TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS
3.1.3
Function of the cell body
65
Learning Objective
By the end of this section, you should be able to:
• explain that the cell body contains the nucleus with its DNA which controls the
activity of the cell.
A neuron is a specialised cell, but it starts life as a normal animal cell. A generalised
animal/plant cell is shown below. Make sure you can label and describe all the parts of
an animal cell, espeically the nucleus, cytoplasm, ribosomes and mitochondria.
A generalised cell
Neurons, like muscle cells, develop long extensions to help them fulfil their functions. A
single neuron may be a metre long in a human.
© H ERIOT-WATT U NIVERSITY
66
TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS
Cell bodies
The cell body contains a nucleus and cytoplasm like a normal cell. It has many
ribosomes that make the proteins which act as neurotransmitters at the gaps, or
synapses, between one neuron and the next. These tiny gaps act like switches and
may allow or prevent signals passing from one neuron to the next. The messengers
which 'jump' between the gaps and pass the signals are called neurotransmitters. There
are also many mitochondria that provide the energy for active transport, which helps
maintain electrical potential and reabsorb neurotransmitters.
The nucleus controls the activity of the cell and carries the DNA coding for the formation
of all proteins in the cell, including those required in the axon terminals which may be
up to a metre distant from the cell body. There is, therefore, a rapid transport system of
microtubules to convey the proteins vital to the functioning the axon terminals.
3.1.4
Function of dendrites
Learning Objective
By the end of this section, you should be able to:
• state that dendrites are stimulated by sense organs or other neurons to carry
impulses towards the cell body.
The diagram below shows the general structure of a neuron. The dendrites are
projections from the cell body or, in some sensory neurons, from the forward extension
of the axon (sometimes called the dendron). Their function is to form synapses with the
axon terminals of other neurons or with cells in sense organs, and to convey impulses
towards the cell body.
General neuron structure showing dendrites
© H ERIOT-WATT U NIVERSITY
TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS
3.1.5
Function of axons
67
Learning Objective
By the end of this section, you should be able to:
• state that the axon ends in many divisions called axon terminals;
• state that the axon carries impulses in one direction from the dendrites to the
axon terminals;
• explain that myelin surrounds the axons, greatly increasing the speed of
conduction of impulses along the nerve fibres as impulses jump from node to
node in the myelin sheath.
Each neuron has only a single axon, which ultimately divides to form several axon
terminals. The axon carries the impulse away from the cell body towards the axon
terminals, which form synapses with the dendrites of the next neurons on the neural
pathway or with effectors such as glands and muscles (neuromuscular junctions).
General neuron structure showing the axon with its myelin sheath
Axons are bundled together to form the nerves that we commonly speak of.
© H ERIOT-WATT U NIVERSITY
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TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS
Nerve bundle with many axons
Electrical impulses transmit signals along these axons. Neurotransmitters take the
information from the dendrite of one cell across the synapse, or gap, to the dendrite of
the next axon. The axons must not leak out signals otherwise confusion would arise as
signals jump from the axon terminal of one neuron to the dendrite of the next neuron.
Additionally, if the signals leaked out, they would become weaker and weaker as they
travelled along the axons; this occurs in people who suffer from illnesses such as MS.
Consequently, they are insulated by layers of myelin sheath, which wraps around the
axon like a Swiss roll.
Neurons: Question
Q2: Complete the sentences by matching the parts on the left with the parts on the
right.
Neurons:
cell body, axon and dendrites.
Neurons receive and transmit:
dendrites.
Neurons comprise:
neuromuscular.
DNA in the cell body codes for:
type of nerve cell.
Carry impulses towards the cell
body:
synaptic cleft.
Axon terminals and dendrites form:
impulses.
The gap between an axon terminal
and a dendrite:
all cell proteins.
Junction between an axon and a
synapses.
muscle fibre:
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3.2
69
Glial cells and myelination
Learning Objective
By the end of this section, you should be able to:
• state that glial cells support and maintain neurons by:
– producing the myelin sheath;
– acting homeostatically to maintain a constant environment around the
neuron;
– removing debris by phagocytosis.
• state that myelination begins in the foetus and continues into adolescence;
• explain that incomplete myelination causes an infant's response to stimuli to be
slower and less co-ordinated than that of older children or adults;
• explain that certain diseases cause a loss of co-ordination by destroying the
myelin sheath, e.g. multiple sclerosis.
This section considers glial cells, the other important type of cell in nerve tissues.
3.2.1
Glial cells
Although they are not neurons, glial cells (also known as neuroglia) are an essential part
of the nervous system. Just as white blood cells are a diverse group of cells, neuroglia
are also a class of cells, each form of which carries out a different function.
One type is found in the central nervous system. If damage occurs to the neurons,
they multiply and remove debris by phagocytosis. Others constantly sample and
homeostatically regulate the chemical environment of the neurons, removing excess
ions and recycling neurotransmitters so that the neuron functions in very constant
conditions.
They are also a key element in the blood-brain barrier, which ensures that only small
molecules, such as O2 , CO2 , and hormones can pass freely between the blood and the
cerebrospinal fluid which bathes the brain. All other molecules, e.g. glucose, must be
actively transported if they are to enter the brain.
Other types of glial cells, including Schwann cells, are responsible for myelination.
These cells closely surround and give physical support to the axon.
Although the term 'nerve cell' is often used when referring to neurons, glial cells are also
important nerve cells and so an effort should be made to always use the correct term
for the neuron.
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Glial cells: Question
Q3:
15 min
Complete the paragraph about glial cells by using words from the list below.
The nervous system contains more than neurons. About 15% of the cells in the
cells which support and maintain the neurons in several ways.
cerebrum are
Some of them monitor the conditions surrounding the neurons and maintain a constant
. Others help repair damage by removing cell debris by
environment by
.
Another cell of this type, called the Schwann cell, wraps lipoprotein membrane around
sheath, the effect of which is to greatly
the
axons forming the
,
conduction of impulses. Starting well before birth, this process, known as
. This explains why an infant's responses to stimuli are less
continues until
than an adult's.
Word list: accelerate, adolescence, coordinated, glial, homeostasis, myelination, myelin,
phagocytosis.
..........................................
3.2.2
Myelination
The myelin is pinched into sausage-shaped pieces at short intervals. The constrictions
are called nodes (nodes of Ranvier). These have a very important function because
they speed up nervous transmission by a factor of 50. Rather than electrical impulses
travelling along axons at 2 metres per second, they move along much faster, jumping
from node to node. The myelin sheath stops sodium and potassium ions from crossing
the membrane so the impulse 'rushes' along to the tiny gap in the myelin where ion
exchange can occur. A myelinated fibre of diameter 18μm and with nodes at 1.5mm
apart will conduct at 100m/s. The larger the diameter, the faster the impulse travels.
Neurons fire on an 'all-or-nothing' basis. If an impulse arriving causes enough of an
effect at the next neuron, it will 'fire'. If the impulse is weak, the next neuron in the
circuit will not fire. However, if a very strong signal arrives, it will not make the signal
passing to the next neuron any larger. The signals from several neurons which have
their synapses together at any adjacent neuron may have summative or, on the other
hand, competitive 'inhibitory' effects. It is repeated firing due to successive signals which
causes a stronger effect, such as a tighter flexing of a muscle. When the impulse leaks
out due to lack of complete myelination, as in MS, repeated firing cannot occur and full
contraction becomes impossible, leading to a weak grip for example.
It is interesting to note that it was this 'all-or-nothing' status of the nervous system,
discovered by biologists a century ago, which led to the development of the binary
revolution called computing.
Slides and micrographs of neurons
15 min
To examine slides and micrographs of neurons, use a computer to perform a Google
image search for "micrograph neurone".
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TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS
Myelination
Myelination begins during the fourth month of pregnancy and continues into
adolescence. As a result, a newly born infant has an immature nervous system. This
explains the initial lack of coordination of responses. The 'bones' of the skull are
incompletely closed, leaving a gap called the fontanelle to allow the brain to continue
to grow for several months after birth. The skeleton is initially made of cartilage. The
flexibility of cartilage, and the mobile nature of the separate 'bones' of the skull, allow
easy passage down the birth canal. Crucially, continued growth of the nervous system,
particularly of the brain, is accommodated. The fontanelle closes between the ages of
18 months and two years. (Recent research has shown that further re-organisation of
the brain seems to occur in the late teens, especially in boys. This explains why we feel
so clumsy for a wee while, then!)
Infancy
Myelination of axons proceeds rapidly during the months after birth. This process is
essential. The axons wrap themselves around lipoprotein derived from cell membranes.
Lack of myelin can have severe consequences. In Muscular Sclerosis (MS), there
is patchy loss of myelin and this leads to delayed or blocked conduction of nervous
impulses.
There are some unmyelinated peripheral neurons that are only encased in cytoplasm
and these are less insulated from leakage of electrical conduction. In addition to
carrying impulses less securely, they are 50 times slower at carrying impulses because
of this lack of insulation. Although impulses do not travel as fast as electricity, or light
and sound waves, they can still achieve speeds of up to 100 metres per second. The
speed of transmission increases with temperature, giving so-called 'warm-blooded'
animals a great advantage over their cold-blooded competitors.
Nerve Transmission
Myelination leads to small nodes forming along an axon. Each node is around 1μm in
diameter and approximately 1mm from its neighbour.
Electrical impulses are carried along axons because the membrane becomes
depolarised and repolarised by active exchange of ions. Depolarisation can 'jump' from
one node to the next in myelinated neurons, whereas it can only flow smoothly and
slowly along unmyelinated neurons.
As new nervous tissue grows, the number of synapses formed between adjacent
neurons multiplies exponentially. It is this massive increase in number of synapses and
the ability to repeatedly fire neurotransmitters across them by means of rehearsal or
repetition that leads to the impressive memory feats and communication skills of
humans.
Myelination: Question
Q4: A myelinated fibre, 18μm in diameter, carries an impulse at 100m/s. Assuming
that an impulse goes a quarter as fast through a fibre (axon) half as wide, how many
seconds does it take for an impulse to travel 2m through an axon of diameter 9μm?
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3.3
Neurotransmitters
Learning Objective
By the end of this section, you should be able to:
• state that neurotransmitters are chemicals which relay signals from neuron to
neuron in the central and peripheral nervous systems;
• state that neurotransmitters also transmit signals between neurons and other
target cells e.g. muscle fibres, endocrine glands;
• state that neurotransmitters are secreted into the gap (the synaptic cleft)
between the neuron and the next cell;
• state that neurotransmitters are stored in vesicles;
• state that the arrival of an impulse causes the release of the neurotransmitters;
• state that neurotransmitters diffuse across the synaptic cleft and bind to
receptors on dendrites;
• state that, if sufficient neurotransmitters attach to the receptors, a threshold is
reached and an impulse is triggered;
• state that signals may be excitatory or inhibitory, depending only on the receptor
on the receiving dendrite and not on the type of neurotransmitter;
• explain that neurotransmitters must be immediately removed to prevent
continuous stimulation of the post-synaptic neurons;
• state that there is a wide range of different chemicals which act as
neurotransmitters, e.g. noradrenalin and acetylcholine;
• state that neurotransmitters are either removed by enzyme action (e.g.
acetylcholine) or by re-uptake (e.g. noradrenalin);
• explain that synapses can filter out weak impulses arising from insufficient
secretion of a neurotransmitter;
• explain that, by summation, a series of weak stimuli can combine to reach the
firing threshold in the post-synaptic neuron.
Neurotransmitters comprise a wide range of chemicals (often amino acids or related
compounds) which transfer the 'message' of the impulse across the gap between
neurons at the synapse or from a neuron to an effector organ such as an endocrine
gland or a muscle.
A synapse between a motor neuron and a muscle cell is called a neuromuscular junction.
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TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS
Neuromuscular junction
Synapses: chemical transmission by neurotransmitters
It is easy to think of synapses simply as gaps between neurons. We cannot have each
muscle and sense organ supplied by its own single neuron from the brain so gaps are
inevitable. Synapses, however, are not merely junctions. They act as filters and must
cope with rapid and repeated firing of neurons. How do they manage this?
3.3.1
Chemical transmission at synapses
Each neuron might be connected to hundreds of other neurons. The dendrites
almost touch. There are thousands of possible permutations of interconnections, each
separated only by a tiny gap. Chemicals called neurotransmitters are secreted at each
synapse. They cross the gap to the post-synaptic dendrite. Will they excite it enough
to fire? Will they inhibit it, effectively switching it off? It all depends on where the
neurotransmitter arrives.
Synapse anatomy
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3.3.2
Neurotransmitters
Chemical messengers, called neurotransmitters, travel across the synaptic cleft to
communicate impulses to the next neuron. The neurotransmitters acetylcholine and
noradrenaline are contained in vesicles in dendrites until they are needed. This
ensures that resources are not wasted and that chemicals are not promoting unwanted
reactions indiscriminately. An impulse arriving at a synaptic terminal stimulates the
synaptic vesicles to secrete their contents by exocytosis into the synaptic cleft. These
neurotransmitters are recognised by receptors on the post-synaptic dendrite.
Neurotransmitters: Questions
Q5:
Give two reasons why neurotransmitters are contained in vesicles.
..........................................
Q6: Why are mitochondria and ribosomes found in large numbers in the pre-synaptic
dendrites?
..........................................
3.3.3
Neurotransmitter threshold
Neurotransmitters work on the basis that the neuron will 'fire' if a certain threshold is
reached. Each neurotransmitter binds to a specific receptor molecule on the adjacent
neuron in a way similar to the lock and key mechanism of enzymes. It is the receptor
which determines whether signals are stimulatory or inhibitory. A tiny quantity of
neurotransmitter has no effect, but a very large quantity has no extra effect. Thus weak
signals are filtered out, but strong signals do not paralyse the nervous system with
excessive contractions. We should remember that each neuron may receive thousands
of synapses from a network of incoming neurons.
As a result, a series of weak stimuli can combine to reach the firing threshold in the
post-synaptic neuron, a process known as summation.
3.3.4
Removal of neurotransmitters
When acetylcholine is released at the synaptic cleft, it binds to the receptors on the
dendrites of the receiving neuron. If the number of excitatory signals exceeds the
number of inhibitory signals, the neuron will 'fire', carrying an impulse to the next
synapse, but this only occurs if a certain threshold is reached. To avoid repeated
contractions from the same stimulus, acetylcholine is immediately destroyed by an
enzyme called acetylcholinesterase. This process is called degradation. This enzyme
was first discovered in an unfortunate individual who had no acetylcholinesterase owing
to a genetic mutation. The breakdown products are reabsorbed by active transport (see
below) using energy from the adjacent mitochondria.
Noradrenaline also needs to be removed, but is not degraded. It is reabsorbed back
into the synaptic ending whence it came. This process is called re-uptake.
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TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS
Diffusion and active transport: Comparison
This activity illustrates the difference between diffusion (a process driven solely by
differences in concentration) and active transport (which uses energy from ATP to move
materials across membranes, even against the concentration gradient).
Diffusion across a membrane is a passive process. The net movement of molecules
across a membrane will stop when the concentration of molecules is the same on both
sides of the membrane, although movement continues.
Diffusion across a membrane
Active transport across a membrane is a process that uses energy. This means that a
concentration gradient can build up across the membrane, which would not be possible
with diffusion.
Active transport across a membrane
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3.3.5
Excitatory and inhibitory transmitters
Noradrenaline and acetylcholine do not by themselves have opposite effects. They act
on different receptor structures, which then mediate their effects on the organs of the
body. It is the receptors in the receiving neuron which are primed to have opposite
effects. Think of yourself as a neurotransmitter acting on light switches in a room. Your
presence can move a switch up or down (neurotransmitter-receptor binding), but which
light goes on, or off, (the effect of the transmitter) depends on how the switch is wired to
the lights.
Acetylcholine from a parasympathetic neuron in the heart will inhibit heart rate and
volume. However, acetylcholine in the alimentary canal promotes peristalsis.
Some acetylcholine receptors also respond to nicotine from cigarettes, often leading to
tobacco addiction in those who smoke. They can also be blocked temporarily by
anaesthetics called muscle blockers (relaxants).
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3.4
77
Neural pathways
Learning Objective
By the end of this section, you should be able to:
• state that a converging pathway is where several neurons pass messages on to
a single neuron;
• state that a converging pathway increases the sensitivity to both excitatory and
inhibitory signals;
• state that rods in the retina are an example of a converging pathway;
• state that a diverging pathway is where a single neuron passes messages on to
several neurons;
• state that a diverging pathway influences several neurons or tissues at the same
time;
• state that fine motor control in the fingers is an example of a diverging pathway;
• state that a reverberating pathway is where neurons later in the pathway
synapse with earlier ones, sending the impulse back through the circuit;
• state that the wake-sleep cycle is an example of a reverberating pathway;
• state that new neural pathways can be developed to:
– create new responses;
– bypass areas of brain damage;
– suppress reflexes;
– suppress responses to sensory impulses.
• state that the development of new neural pathways creates a plasticity of
response.
The multiplicity of neuron connections confers further advantages. In some cases,
converging pathways increase the strength of a signal, whilst in others, diverging
pathways allow a signal from a specific area to be distributed to a group of neurons. In
reverberating pathways, positive feedback causes continuous stimulation of the neurons.
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Neural pathways: Comparison
Convergent pathway
Divergent pathway
Reverberating pathway
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TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS
3.4.1
A converging pathway
In the retina of the human eye, there are cone-shaped neurons which can only be fired
by a high intensity of light. They respond to colour and only fire in bright light. Their
neural pathways show little convergence. Each neuron synapses with one other neuron
as it takes the message to the brain. However, rod-shaped neurons take up most of
the retina. They are fired by dim light. Thus each has a weak impulse. However, many
rods converge to synapse with a single neuron. Summation at the synapses causes the
several weak stimuli to fire the neuron, allowing rods to give us a monochrome view in
dim light.
Notice in the diagram below that the incoming light has to pass through the layer of nerve
tissue before reaching the photoreceptor cells. This is an example of 'not-very-intelligent'
design!
Retina of an eye showing rods and cones
3.4.2
A diverging pathway
Fine motor control of the hand is brought about by a single impulse from a neuron in the
motor area of the brain. The neuron synapses with a group of neurons which carry the
signal on, eventually causing contraction in the groups of skeletal muscles that control
the hand and fingers.
3.4.3
A reverberating pathway
In some neural pathways, branches of some axons extend backwards towards the
source of the impulse, causing the earlier neurons in the pathway to be continuously
stimulated. As a result, once stimulated, the pathway continues to stimulate itself.
Such pathways are found in the brain-controlling rhythmic activities, such as breathing
and the sleep-wake cycle, muscular coordination and consciousness.
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3.4.4
Plasticity of response
After an injury such as a stroke, the brain can adapt, especially if therapy is quickly
available. The function of a damaged part may be taken over by another, demonstrating
plasticity (adaptability) of function. This is referred to as major plasticity. Minor plasticity
refers to occasions when portions of the brain can be temporarily 'shut down'. Examples
of the latter include suppressing a reflex sneeze or when workers in a distillery 'ignore'
the smell of the mash after a while.
This plasticity of response is created by the development of new neural pathways. As a
result, the brain can bypass damaged areas, create new responses, and suppress both
reflexes and the response to sensory stimuli.
Suppressing brain reflexes
5 min
Carry out an investigation into the ability of the brain to suppress reflexes or sensory
impulses.
For example, gently release the air from a balloon into your eye and see if you can
suppress reflex blinking.
Background information is given below, in case you would like to know how a reflex
works, though this is not necessary for the exam.
Background information
It is interesting to note that special relay neurons exist in the spinal cord to allow shortcircuiting of normal response times in occasions of danger. Relay neurons short-circuit
the normal pathway to the brain. The message will continue to travel to the brain, though
a response will already have occurred, avoiding danger. In your experiment, you should
show that plasticity of response can allow you to over-ride the reflex response.
The classic reflex response is obtained by tapping the flexed knee which will kick out
involuntarily.
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TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS
Reflex action in a knee
This apparently artificial reflex is in fact one which helps us regain balance, straightening
our legs (and arms) after a trip or slip has caused our legs to bend at the knee. This
stimulates the stretch receptors in the quadriceps and triggers the reflex.
..........................................
Neural pathways: Questions
Q7: Pathway where several neurons pass messages to one:
a) converging
b) diverging
c) reverberating
..........................................
Q8: Pathway where a single neuron passes messages on to several:
a) converging
b) diverging
c) reverberating
..........................................
Q9: Pathway where messages are passed back to earlier neurons:
a) converging
b) diverging
c) reverberating
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TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS
Q10: Pathway involving rods in the retinas:
a) converging
b) diverging
c) reverberating
..........................................
Q11: Pathway giving fine motor control in the fingers:
a) converging
b) diverging
c) reverberating
..........................................
Q12: Pathway controlling the wake-sleep cycle:
a) converging
b) diverging
c) reverberating
..........................................
Q13: New neural pathways create:
a) brain damage
b) plasticity
..........................................
Q14: New neural pathways bypass:
a) brain damage
b) plasticity
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TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS
3.5
Learning points
Summary
Neurons
• The nervous system comprises a range of different cells called neurons.
• Neurons are grouped together to form the brain and spinal cord of the
central nervous system, and the nerves of the peripheral nervous system.
• Neurons receive and transmit impulses (a form of electrical signal).
• There are three main types of neuron: sensory neurons, motor neurons and
interneurons.
• Sensory neurons carry impulses into the Central Nervous System (CNS)
from sense organs.
• Motor neurons carry impulses out from the CNS to effectors such as
muscles and glands.
• Interneurons are found in the CNS where they connect with other neurons.
• A neuron consists of a cell body with protruding fibres, in the form of one
axon and many dendrites.
• The cell body contains the nucleus with its DNA, which controls the activity
of the cell.
• Dendrites are stimulated by sense organs or other neurons to carry
impulses towards the cell body.
• The axon ends in many divisions called axon terminals.
• The axon carries impulses in one direction from the dendrites to the axon
terminals.
• Myelin surrounds the axons, greatly increasing the speed of conduction of
impulses along the nerve fibres as impulses jump from node to node in the
myelin sheath.
Glial Cells and Myelination
• Glial cells support and maintain neurons by:
– producing the myelin sheath;
– acting homeostatically to maintain a constant environment around the
neuron;
– removing debris by phagocytosis.
• Myelination begins in the foetus and continues into adolescence.
• Incomplete myelination causes an infant's response to stimuli to be slower
and less co-ordinated than that of older children or adults.
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TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS
Summary Continued
• Certain diseases cause a loss of co-ordination by destroying the myelin
sheath, e.g. multiple sclerosis.
Neurotransmitters
• Neurotransmitters are chemicals which relay signals from neuron to neuron
in the central and peripheral nervous systems.
• Neurotransmitters also transmit signals between neurons and other target
cells, e.g. muscle fibres, endocrine glands.
• The junction between neurons is called a synapse.
• The gap between one neuron and the next is called the synaptic cleft.
• The junction between neurons and muscle cells is called a neuromuscular
junction.
• Neurotransmitters are secreted into the gap, the synaptic cleft, between the
neuron and the next cell.
• Neurotransmitters are stored in vesicles.
• The arrival of an impulse causes the release of the neurotransmitters.
• Neurotransmitters diffuse across the synaptic cleft and bind to receptors on
dendrites.
• If sufficient neurotransmitters attach to the receptors, a threshold is reached
and an impulse is triggered.
• Signals may be excitatory or inhibitory, depending only on the receptor on
the receiving dendrite and not on the type of neurotransmitter.
• Neurotransmitters must be immediately removed to prevent continuous
stimulation of the post-synaptic neurons.
• There is a wide range of different chemicals which act as neurotransmitters,
e.g. noradrenalin and acetylcholine.
• Neurotransmitters are either removed by the action of an enzyme (e.g.
acetylcholine) or by re-uptake (e.g. noradrenalin).
• Synapses can filter out weak impulses arising from insufficient secretion of
neurotransmitter.
• By summation, a series of weak stimuli can combine to reach the firing
threshold in the post-synaptic neuron.
Neural Pathways
• A converging pathway is where several neurons pass messages on to a
single neuron.
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85
Summary Continued
• A converging pathway increases the sensitivity to both excitatory or
inhibitory signals.
• Rods in the retina are an example of a converging pathway.
• A diverging pathway is where a single neuron passes messages on to
several neurons.
• A diverging pathway influences several neurons or tissues at the same time.
• Fine motor control in the fingers is an example of diverging pathways.
• A reverberating pathway is where neurons later in the pathway synapse with
earlier ones, sending the impulse back through the circuit.
• The wake-sleep cycle is an example of a reverberating pathway.
• New neural pathways can be developed to:
– create new responses;
– bypass areas of brain damage;
– suppress reflexes;
– suppress responses to sensory impulses.
• The development of new neural pathways creates a plasticity of response.
3.6
Extended response question
The activity which follows presents an extended response question similar to the style
that you will encounter in the examination.
You should have a good understanding of sensory and motor neurons before attempting
the question.
You should give your completed answer to your teacher or tutor for marking, or try to
mark it yourself using the suggested marking scheme.
Extended response question: Sensory and motor neurons
Compare and contrast sensory and motor neurons and describe events that occur at a
synapse. (10 marks)
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3.7
End of topic test
End of Topic 3 test
Q15: Complete the sentences by matching the parts on the left with the parts on the
right. (10 marks)
Cells that make up the nervous system:
myelin.
Transmitted through the nervous system:
dendrites.
Neurons that carry information into the CNS:
motor neurons.
Neurons that connect neurons:
multiple sclerosis.
Neurons that connect the CNS to glands:
glial.
Carry impulses towards the cell body:
axon terminals.
Found at the end of the axon:
sensory.
Increases speed of conduction of impulses:
interneurons.
Cells which produce the myelin sheath:
neurons.
impulses.
Results from destruction of the myelin sheath:
..........................................
Q16: Complete the paragraphs by selecting words from the list. (15 marks)
in the CNS and
Neurotransmitters are chemicals which relay signals between
. The junction between neurons is called a
between neurons and
and that between neurons and muscle fibres is a
junction. Neurotransmitters
into synaptic cleft, and
across the gap and bind
are secreted by
of the next neuron.
to receptors on the
, depending only on the
on the
Signals may be excitatory or
receiving dendrite and not on the type of neurotransmitter. Neurotransmitters must be
of the post-synaptic neurons.
immediately removed to prevent continuous
action (e.g. acetylcholine) or by
Neurotransmitters are either removed by
).
re-uptake (e.g.
Synapses can filter out weak impulses arising from
neurotransmitter.
secretion of
is reached and an
If sufficient neurotransmitters attach to the receptors, a
a series of weak stimuli can combine to reach the
impulse is triggered. By
firing threshold in the post-synaptic neuron.
Word list: dendrites, diffuse, enzyme, exocytosis, glands, inhibitory, insufficient,
neuromuscular, neurons, noradrenalin, receptor, stimulation, summation, synapse,
threshold.
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TOPIC 3. NEURONS, NEUROTRANSMITTERS AND NEURAL PATHWAYS
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Q17: Complete the sentences by matching the parts on the left with the parts on the
right. (9 marks)
Several neurons pass messages on to a single neuron:
reverberating
pathway.
An example of a converging pathway:
fine motor control.
Increased by a converging pathway:
converging pathway.
A single neuron passes messages on to several neurons:
wake-sleep cycle.
An example of a diverging pathway:
new neural
pathways.
Neurons later in the pathway synapse with earlier ones:
plasticity of
response.
An example of a reverberating pathway:
rods in the retina.
New responses are created by their development:
sensitivity to signals.
Result of the development of new neural pathways:
diverging pathway.
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..........................................
The following diagram represents a neuron in the central nervous system.
Q18: Identify the structures labelled A. (1 mark)
..........................................
Q19: Identify the structure labelled B. (1 mark)
..........................................
Q20: Identify the structures labelled C. (1 mark)
..........................................
Q21: Where is myelin found on a neuron and what is its function? (2 marks)
..........................................
Q22: Which type of neuron conducts impulses between the CNS and effector organs?
(1 mark)
..........................................
Q23: Interneurons conduct impulses between what? (1 mark)
..........................................
Q24: Which type of neuron conducts impulses between sense organs and the CNS? (1
mark)
..........................................
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Q25: What is the gap between neurons called? (1 mark)
..........................................
Q26: What joins a neuron to a muscle fibre? (1 mark)
..........................................
Q27: List three functions of glial cells. (3 marks)
..........................................
Q28: Name a disease that destroys the myelin sheath and describe its effect. (2 marks)
..........................................
Q29: Where are neurotransmitters stored? (1 mark)
..........................................
Q30: What causes the release of neurotransmitters? (1 mark)
..........................................
Q31: How do neurotransmitters cross between neurons? (1 mark)
..........................................
Q32: What do neurotransmitters bind to? (1 mark)
..........................................
Q33: Explain the process of summation. (2 marks)
..........................................
Q34: What type of pathway involves several neurons passing messages to one neuron?
(1 mark)
..........................................
Q35: Give an example of the above type of pathway. (1 mark)
..........................................
Q36: Describe the neuron connections of a diverging pathway, an example of which is
the fine motor control of the fingers. (1 mark)
..........................................
Q37: What type of pathway has neurons later in the pathway that synapse with earlier
ones? (1 mark)
..........................................
Q38: Give an example of the above type of pathway. (1 mark)
..........................................
Q39: What is created by the development of new neural pathways? (1 mark)
..........................................
Q40: State two results of the development of new neural pathways. (2 marks)
..........................................
..........................................
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Topic 4
Neurotransmitters, mood and
behaviour
Contents
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2 Dopamine and the reward pathway . . . . . . . . . . . . . . . . . . . . . . . . .
92
93
4.3 Endorphins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
94
4.4 Neurotransmitter-related disorders and their treatment . . . . . . . . . . . . . .
4.4.1 Drugs used to treat neurotransmitter-related disorders . . . . . . . . . .
95
96
4.4.2 Neurotransmitter-related disorders and their treatment . . . . . . . . . .
4.5 Mode of action of recreational drugs . . . . . . . . . . . . . . . . . . . . . . . .
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100
4.5.1 Modes of action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.6 Drug addiction, sensitisation and tolerance . . . . . . . . . . . . . . . . . . . .
101
103
4.7 Learning points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.8 Extended response question . . . . . . . . . . . . . . . . . . . . . . . . . . . .
105
106
4.9 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
107
Learning Objectives
By the end of this topic, you should be able to:
• describe the role of dopamine in the reward pathway of the brain;
• describe the role of endorphins in the body and the factors which increase their
production;
• explain how neurotransmitter-related disorders are treated;
• explain the mode of action of recreational drugs;
• explain the causes of drug addiction and tolerance.
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4.1
Introduction
Certain neurotransmitters are particularly associated with the control of mood and
behaviour. Mood is a psychological state which is less immediately affected by events
than emotion, and less permanent than personality or temperament. Behaviour is the
response of an organism to internal and external stimuli.
In particular, we will consider the role of the neurotransmitters dopamine and
endorphins. While these are both produced and exert an effect outside, as well as
inside, the brain, we will restrict our study to their actions in the brain as this is where
mood and behaviour are determined. Within the brain, they act not only in the cerebrum,
but also in those areas of the mid-brain located in the vicinity of the hypothalamus.
Dopamine causes feelings of pleasure and euphoria, and, consequently, any activity
which induces dopamine release will tend to be repeated. It is therefore associated with
beneficial behaviours, such as eating when hungry. This reward pathway is also used
in training and teaching. The action of dopamine, particularly in relation to the reward
pathway, is central to many of the other subjects in this topic.
Endorphins are a group of at least twenty related chemicals which are produced from the
pituitary and the hypothalamus in response to a variety of different stimuli, both physical
and mental. They act like the opiate drugs after which they are named, relieving pain
and creating a feeling of well-being. This effect is achieved because the increased levels
of endorphins in turn stimulate the release of dopamine.
A wide range of medical conditions are linked to neurotransmitters, associated both with
their under- and over-production. Treatment of these disorders can be complicated by
the inability of the neurotransmitters involved to cross the blood-brain barrier.
An immense variety of chemicals can affect or imitate the action of neurotransmitters,
especially in the reward pathway. Where these are consumed voluntarily because of the
mood they induce, they are referred to as recreational drugs. Some are administered
medicinally as analgesics to control pain, e.g. morphine, an opioid derived from
the Opium Poppy (Papaver somniferum). Exposure to such chemicals, especially if
regularly repeated or prolonged, leads to addiction and/or to tolerance. Addiction may
be in the form of a physiological or a psychological dependence; tolerance means that
increasingly large doses of the chemical are needed to achieve the same effect.
In order to put some flesh on the bare bones of the syllabus, the names of some of
the enzymes and chemicals involved under the following sections have been included,
although they are not required knowledge. These can be quite long and daunting so
have been broken up to emphasise the sense of the word - please do not feel patronised
by this, and certainly do not try to learn them!
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4.2
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Dopamine and the reward pathway
Learning Objective
By the end of this section, you should be able to:
• state that the reward pathway involves neurons which secrete or respond to the
neurotransmitter dopamine;
• explain that dopamine induces the feeling of pleasure and so reinforces
particular behaviours;
• explain that the reward pathway is activated by beneficial behaviour, e.g. eating
when hungry.
A reward is something that when supplied after a piece of behaviour causes that
behaviour to be increased or repeated. In training, this is called reinforcement. The
neurons of the reward pathway (or system) are located in the mid-brain below the
cortex, linking to the areas at the base of the cortex and in the frontal areas of the
cortex. The activation of this pathway by beneficial actions such as feeding, sexual
contact, or successful aggression, must have developed very early in our evolution.
The neurotransmitter principally associated with the reward pathway is dopamine, a
relatively simple organic molecule. Dopamine also plays many other roles in the brain,
being involved in behaviour, cognition, punishment, motivation, voluntary movement,
sleep, mood, attention, learning, and working memory. In the reward pathway, dopamine
secretion causes feelings of pleasure and euphoria (happiness and contentment). As
all types of reward seem to increase the level of dopamine secretion in the brain, a
good definition of a reward would be something that increases dopamine secretion in
the reward pathway.
Dopamine and the reward pathway: Question
Q1: Explain why linking a behaviour with activation of the reward pathway would be
important in evolutionary terms.
..........................................
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4.3
Endorphins
Learning Objective
By the end of this section, you should be able to:
• state that endorphins stimulate the neurons that are involved in reducing the
intensity of pain;
• explain that increased levels of endorphins are connected with euphoric
feelings, appetite modulation and the release of sex hormones;
• state that increased endorphin production is associated with severe injury,
prolonged continuous exercise, stress and consumption of certain foods.
Endorphins are opioid peptides, their name being a strong clue as to their action; it is
an amalgam of 'endogenous' and 'morphine', and reflects the fact that their chemical
structure and effect are very similar to that of morphine. They are a family of some
twenty compounds, which are divided into four types depending on the number of amino
acids which they contain, known as alpha- (α), beta- (β), gamma- (γ) and sigma- (σ)
endorphins. Of these, the β-endorphins are the most powerful and usually act in the
hypothalamus and the pituitary gland.
Endorphins attach to opioid receptors on neurons, and, depending on which type and
where, they act to reduce pain or to increase euphoria.
When they attach to neurons connected to pain receptors (nociceptors) they act as
inhibitors, making it less likely that an impulse will be transmitted. Pain is the body's
method of telling you that you have done some damage to yourself (headaches and
period pains aside); if that damage is severe, then the increased release of endorphins
reduces the perceived pain, helping the body to continue to function.
Another cause of increased endorphin production is prolonged intense physical activity;
intense here meaning that the activity is at a level which makes breathing difficult. One
consequence of this is that during a hard training session, it is possible to do damage
which only later becomes apparent. Any-one who has played a contact sport will know
how sore an injury can seem in the hours after the game ends, even though it was
scarcely noticed when it occurred. As endorphin secretion falls, so the impulses in the
pain circuits increase.
The release of endorphins during such challenging exercise also accounts for the feeling
of euphoria experienced afterwards, the 'runner's high'. This is a result of endorphins in
the reward system attaching to a different set of opioid receptors, with two outcomes:
1. firstly, the production of the inhibitory neurotransmitter GABA (gamma-aminobutyric acid) is itself inhibited so that impulses are more likely to be generated
(GABA is used at the great majority of fast inhibitory synapses in nearly every part
of the brain) - many sedative/tranquillising drugs act by enhancing its effects;
2. secondly, the release of dopamine is stimulated.
Together these have the effect of greatly increasing the number of impulses in the reward
pathway.
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Increased endorphin production has also been linked to the consumption of dark
chocolate and spicy food, both of which can become quite addictive. Sexual orgasm
also raises endorphin levels, as does the physical closeness of a loved one.
Research has also suggested that endorphins play a role in appetite modulation (the
control of food consumption), the release of sex hormones, and the body's reaction to
stress.
Endorphins: Questions
Q2: Explain how endorphins reduce the sensation of pain.
..........................................
Q3: Give an example, with an explanation, of situations in which pain suppression is
beneficial and detrimental.
..........................................
Q4: The lack of a satisfying sexual relationship is a major factor in the breakdown of
many marriages. What have endorphins got to do with this?
..........................................
4.4
Neurotransmitter-related disorders and their treatment
Learning Objective
By the end of this section, you should be able to:
• state that neurotransmitter-related disorders arise from the under- or overproduction of neurotransmitters, or an imbalance in their production;
• state that many of the drugs used to treat these disorders are similar to
neurotransmitters;
• explain that agonists bind to and stimulate receptors, thus mimicking the
neurotransmitter;
• explain that antagonists bind to specific receptors, blocking the action of a
neurotransmitter;
• state that other drugs inhibit the enzymes which degrade neurotransmitters or
inhibit re-uptake.
Given the wide variety of neurotransmitters and the equal diversity of receptors,
it should be unsurprising that there are a considerable range of neurotransmitterrelated disorders, some of which are well known, e.g. Alzheimer's and Parkinson's
diseases, others less so, e.g. myasthenia gravis. There can be either over- or underproduction of the neurotransmitter, or an imbalance between the production of different
neurotransmitters which operate together (e.g. one being inhibitory and the other
excitatory). In other cases, it may be that receptors are blocked so that neurotransmitters
cannot bind to them.
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Consequently, many of the drugs used to treat these conditions are similar to the
neurotransmitters which are present in abnormal levels.
4.4.1
Drugs used to treat neurotransmitter-related disorders
Among the drugs used to treat these disorders are agonists, antagonists and inhibitors.
Agonists are chemicals which mimic the action of a neurotransmitter by binding to
its receptor and triggering a response in the corresponding neuron. Drugs which are
agonists therefore have a similar effect on the natural agonist, the neurotransmitter.
Antagonists are chemicals which bind to the receptors and prevent the neurotransmitter
from so doing. Similarly to enzyme inhibitors, they may exert their effect by binding to
the active site of the receptor in competition with the neurotransmitter, later separating
from the active site. However, some antagonists bind permanently to the active site,
preventing it ever subsequently receiving a neurotransmitter. Also, similarly to enzyme
inhibitors, some antagonists bind to a part of the receptor other than the active site (an
allosteric site), distorting the shape of the active site and preventing neurotransmitters
from binding.
Enzyme inhibitors may be used either to act on the enzymes which break
down the neurotransmitters at the synapse (e.g. acetyl cholin esterase) or which
inhibit the re-uptake of the neurotransmitter into the presynaptic neuron (e.g.
nor adrenaline/norepinephrine, dopamine).
4.4.2
Neurotransmitter-related disorders and their treatment
Although you are not required to know the details of any particular disorders or their
treatment, a selection are included below to illustrate why particular drugs are used in
each case. It should be remembered that these are common conditions and that we will
all come across them at some point in our lives, either personally or in people close to
us. It should be understood that there is much current research into these conditions,
and that the hypotheses about their causes and the types of treatment available are
constantly evolving.
Alzheimer's Disease
Alzheimer's Disease is the most common cause of dementia, i.e. the premature
deterioration of mental faculties. Although most commonly found in people aged 65
or over, it may occasionally develop much earlier. The disease causes a loss of neurons
releasing acetylcholine in parts of the cerebral cortex and their associated mid-brain
areas, and the development of clumps of amino acids known as plaques. The onset
of the condition can be delayed by taking part in intellectual activities such as bridge,
chess or music, which not only help to keep the brain active, but also promote social
interaction which can be beneficial.
There is no cure for the disease at present, but the symptoms can be ameliorated by the
use of drugs. One of these is an acetyl cholin esterase inhibitor, which slows the rate
at which acetylcholine is degraded, thus maintaining its concentration in the synapses,
despite the reduction in its production.
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Parkinson's Disease
Parkinson's Disease is also a degenerative disorder which is most often found in
people over 50 years old. The most obvious early symptoms of the disease are
shaking, slowness and difficulty of movement. Later, there develop difficulties in mental
functioning. One of its causes is the failure of the mid-brain to produce sufficient
quantities of dopamine as a result of cell death; towards the end of the course of the
disease, nearly three-quarters of the cells in this area may be affected. The overall
effect of this is to reduce the flow of impulses to the relevant areas of the cortex, thus
increasing the effort required to carry out any given activity.
An illustration of Parkinson's disease by William Richard Gowers, which was first
published in A Manual of Diseases of the Nervous System (1886)
Again, there is currently no cure for the condition, but different drugs can ameliorate the
symptoms at any given stage in its development:
• L-DOPA (L-3,4-di hydroxy phenylalanine) is the precursor of the inter-related
neurotransmitters dopamine, noradrenaline (norepinephrine) and adrenaline
(epinephrine) - unlike dopamine, it can cross the blood-brain barrier in significant
quantities and so can be injected into the blood stream and reach the brain, where
it is converted into dopamine;
• dopamine agonists are drugs which attach to the dopamine receptors and trigger
impulses in the relevant neurons;
• mono amine oxidase inhibitors (MAO-B inhibitors) raise the level of dopamine by
acting on the enzyme mono amine oxidase-B, which degrades dopamine in the
synapse;
• the introduction of adult neural stem cells also represents a possible future
treatment - these cells might be able to be introduced into the brain to replace
the lost dopamine-secreting neurons.
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Schizophrenia
Schizophrenia is a condition which has both genetic and environmental origins. The
genetic component involves the action of several genes (multifactorial inheritance), and,
as such, can exert a wide range of levels of influence. The prime environmental influence
is drug abuse, with cannabis being most important, although cocaine and amphetamines
are also strongly implicated. Other environmental factors may play a role, e.g. growing
up in an urban environment doubles the likelihood of the condition developing. The
typical symptoms of schizophrenia are delusions, disordered thoughts and speech,
hallucinations, poor emotional responses, limited speech, social isolation, and lack of
motivation.
Risperidone (trade name Risperdal) is a common a typical antipsychotic medication
used in the treatment of schizophrenia
Until recently, it was thought that the neurological cause of schizophrenia was overstimulation of the dopamine receptors in the reward pathway, which was discovered
when dopamine antagonist drugs were found to reduce the symptoms of the conditions.
Other neurotransmitters (serotonin and glutamate) are now thought to also be involved.
Depression
Depression in the clinical sense should not be confused with feeling depressed and
generally down about the world. Clinical depression has a serious impact on nearly all
aspects of life, including relationships, work, sleep, eating and general health. Typically,
the symptoms are very low mood, loss of enjoyment, and a sense of worthlessness and
guilt.
There are several hypotheses about the neurological cause of depression. In particular,
a part of the brain stem close to the medulla has been implicated. In this area,
serotonin secretion is suggested as having a regulatory role in relation to the other
neurotransmitters norepinephrine (noradrenaline) and dopamine so that low serotonin
levels will in turn reduce their secretion. This gives the key to one approach to the
treatment of depression. Norepinephrine is reabsorbed into the presynaptic axon
terminal so that its concentration is raised by drugs, which inhibit its re-uptake. In
contrast, dopamine is degraded by enzymes in the synapse so, as in the treatment
of Parkinson's Disease, monoamine oxidase (MAO-B) inhibitors are used to increase its
concentration.
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Generalised anxiety disorders
Generalised anxiety disorders arise from a malfunction in the amygdala regions in the
lower central area of each cerebral hemisphere, which are especially concerned with the
feelings of fear and anxiety. The condition is characterised by excessive and irrational
long-lasting worry about everyday matters, expressing itself in a very wide range of
symptoms, including fatigue, breathing difficulties and insomnia.
One suggested cause is an imbalance between the neurotransmitters serotonin and
norepinephrine. One treatment may be to administer drugs which act as agonists on
the gamma-amino butyric acid (GABA) receptors - as GABA is the principal inhibitory
neurotransmitter in the body, this has the effect of reducing the stimulation of the neurons
in the amygdale. Beta-blockers may also be used as a treatment; as their name implies,
they are antagonists which attach to norepinephrine receptors (beta-receptors being
one of several types), thus reducing the excitatory effect of the neurotransmitter in the
amygdala.
Neurotransmitter-related disorders and their treatment: Question
Q5: Complete the following table about neurotransmitter-related diseases.
Disorder
Area of brain
affected
Neurotransmitters
involved
Alzheimer's
disease
Parkinson's
disease
Schizophrenia
Generalised
anxiety disorder
Depression
..........................................
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4.5
Mode of action of recreational drugs
Learning Objective
By the end of this section, you should be able to:
• explain that many recreational drugs affect neurotransmission in the reward
pathway;
• state that changes in neurochemistry alter mood, cognition, perception and
behaviour;
• state that recreational drugs may:
– stimulate the release of neurotransmitters;
– imitate the action of neurotransmitters (agonists);
– block the binding of neurotransmitters to their receptors (antagonists);
– inhibit the re-uptake of neurotransmitters;
– inhibit the enzymatic degradation of neurotransmitters.
Drugs which are referred to as recreational are introduced into the body either because
they generate pleasurable sensations in of themselves, or because they enhance some
other leisure experience. They are also taken in other circumstances, e.g. to help cope
with pain or other conditions.
The list of chemicals which may be consumed in this way is staggering, and ever
expanding. In nearly all cases, the use or possession of these substances is illegal
in all countries. Major exceptions are the mild stimulants caffeine (tea, coffee, cocoa)
and nicotine (all forms of tobacco), and the depressant ethanol. The use of caffeine
is universally unregulated (although proscribed by certain religions), whereas the
availability of tobacco and alcohol are usually regulated to some extent. All three
are addictive and higher levels of intake are needed to achieve the same effect with
continued use (otherwise known as tolerance). So-called 'legal highs' are usually
newly synthesised compounds related to existing illegal ones or newly discovered plant
substances. The fact that the law has not caught up with them does not indicate that
they are safe to consume!
Caffeine
Caffeine is the mostly widely used psychoactive drug in the world. It does not attract
legal restrictions because its stimulant effects are relatively mild. Nevertheless, it does
raise blood pressure and disrupts sleep, both of which can lead to serious complications.
The classic image below of the effect of caffeine on a spider's efforts to spin a web
should give us pause for thought.
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The effect of caffeine on spider web construction
(Noever, R., J. Cronise, and R. A. Relwani. 1995. Using spider-web patterns to
determine toxicity. NASA Tech Briefs 19(4))
Ethanol
Ethanol is the most widespread drug which is abused. In those countries where its
consumption is legal, it is frequently drunk in quantities which are potentially harmful, its
long-term consumption causes considerable expense to health services, and the side
effects on society of its misuse in terms of violence (domestic and otherwise), crime and
loss of working time are huge. It is probable that it only remains legal because its use
is so widespread and deeply woven into society that the public support that would be
required to make a ban successful would be lacking (as was the case in the USA during
the Prohibition years of the 1920s).
Tobacco
While not having the social dimension of alcohol abuse, smoking tobacco causes
serious damage to the smoker's health and to those around them. For this reason,
the practice is being increasingly regulated in many parts of world. Unlike ethanol, the
nicotine stimulant present in tobacco is not the cause of the health problems, in the
sense that the strong addiction which quickly develops does not itself damage health.
Rather, it is the actual smoking process which releases a wide range of chemicals which
cause cancers, and pulmonary and cardiovascular disease.
4.5.1
Modes of action
Most recreational drugs target the brain's reward system, directly or indirectly, and cause
it to be flooded with dopamine. When some drugs are taken, they can cause dopamine
secretion at levels up to ten times those caused by natural rewards, which strongly
motivates people to repeat the act. In a sense, this unnatural over-stimulation of the
reward circuit will teach us to abuse drugs. This quickly leads to addiction and so, by
definition, all recreational drugs are addictive.
As mentioned in an earlier section, while the effect of increased dopamine secretion
in the reward pathway is to cause feelings of pleasure and euphoria, dopamine
also plays many other roles in the brain, being involved in behaviour, cognition,
punishment, motivation, voluntary movement, sleep, mood, attention, learning, and
working memory. Consequently, the effects of recreational drugs run far beyond the
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immediate sensations for which they are consumed, having widespread and profound
effects on the neurochemistry of the brain.
The modes of action of recreational drugs are very similar to those of the drugs used to
treat neurotransmitter-related disorders.
Stimulating the release of neurotransmitters
MDMA (ecstasy) increases the level of the neurotransmitter serotonin by stimulating its
release from the synaptic vesicles of neurons, and also inhibiting its re-uptake. The
increased secretion of serotonin in the reward pathway in turn stimulates increased
production of dopamine and norepinephrine, with their associated euphoric effects.
Nicotine binds to certain acetylcholine receptors, stimulating the production of several
neurotransmitters including dopamine, which leads to the feelings of euphoria and
relaxation, and to addiction.
In addition, nicotine stimulates the secretion of
adrenaline/epinephrine, thus causing increases in blood pressure, breathing and heart
rates, and higher blood sugar levels.
Agonists
Cannabis attaches to receptors in the neurons of the brain which naturally bind the
endocannabinoid neurotransmitters produced in the brain. These receptors are
located on the presynaptic neuron. The effect of their binding to cannabis is to suppress
the secretion of the inhibitory neurotransmitter GABA, thus increasing stimulation of
impulses in the reward pathway.
Ethanol acts as an agonist in the central nervous system by binding to the GABA
receptors, depressing the flow of impulses in the postsynaptic neuron. The more GABA
receptors that are stimulated, the less the chance of an impulse being generated. As
GABA is the most widespread neurotransmitter which causes inhibition in the brain, this
explains the effect of ethanol on so many different aspects of behaviour.
Antagonists
Ethanol is also an antagonist of the glutamate receptor NMDA which plays a key role
in memory; this is thought to explain the memory loss associated with even quite low
levels of alcohol consumption.
Inhibition of re-uptake of neurotransmitters
Cocaine blocks the re-uptake of serotonin, norepinephrine and dopamine by binding
to the transporter molecules that effect their re-absorption into the presynaptic neuron.
Consequently, the levels of these chemicals are increased in the synapses, but the
actual effect depends on the cells in which the receptors are located.
Inhibition of degradation of neurotransmitters
As well as nicotine, tobacco smoke contains two monoamine oxidase (MAO) inhibitors.
Due to the fact that MAOs are the enzymes which break down the neurotransmitters
dopamine, norepinephrine and serotonin, the effect is to boost the euphoric sensation
associated with tobacco smoking and cause most of its addictive properties.
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Modes of action: Question
Q6: Complete the following table about the mode of action of drugs.
Mode of action
Drug
Neurotransmitter
Stimulating the release of
neurotransmitters
Agonists
Antagonists
Inhibition of re-uptake of
neurotransmitters
Inhibition of degradation of
neurotransmitters
..........................................
4.6
Drug addiction, sensitisation and tolerance
Learning Objective
By the end of this section, you should be able to:
• state that changes in the number and sensitivity of receptors underlie addiction
and tolerance;
• state that sensitisation is an increase in the number and sensitivity of receptors;
• state that sensitisation results from exposure to antagonist drugs;
• state that sensitisation leads to addiction;
• state that desensitisation is a decrease in the number and sensitivity of
receptors;
• state that desensitisation results from exposure to agonist drugs;
• state that desensitisation leads to tolerance.
Whereas the hyperstimulation of the reward pathway generates a psychological
dependence on a drug (often after only a few encounters with it), long-term abuse of
a drug leads to changes in the nervous system which make the addiction physiological
as well. This may take two forms.
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• Sensitisation, in which the effect of the drug increases with repeated exposure
to it, i.e. the same dose has an increased effect the more often it is taken. At the
level of the neurons, the effect results from an increase in the number of receptors
and an increase in their sensitivity to the drug. This is caused by drugs that act as
antagonists and is associated with the severe withdrawal symptoms experienced
when giving up some drugs, e.g. alcohol.
• Desensitisation, in which the effect of the drug reduces with repeated exposure.
In this case there is a decrease in the number and sensitivity of receptors, and
the drugs involved are agonists. The result is drug tolerance, in which increasing
doses of the drug are required to achieve the same effect, e.g. heroin.
Drug addiction, sensitisation and tolerance: Questions
Q7:
What underlies drug addiction and tolerance?
..........................................
Q8:
What causes sensitisation?
..........................................
Q9:
What drugs cause sensitisation?
..........................................
Q10: To what does drug sensitisation contribute?
..........................................
Q11: What causes desensitisation?
..........................................
Q12: What drugs cause desensitisation?
..........................................
Q13: What does desensitisation cause?
..........................................
© H ERIOT-WATT U NIVERSITY
TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR
105
..........................................
4.7
Learning points
Summary
Dopamine and the reward pathway
• The reward pathway involves neurons which secrete or respond to the
neurotransmitter dopamine.
• Dopamine induces the feeling of pleasure and so reinforces particular
behaviours.
• The reward pathway is activated by beneficial behaviour, e.g. eating when
hungry.
Endorphins
• Endorphins stimulate neurons involved in reducing the intensity of pain.
• Increased levels of endorphins are connected with euphoric feelings,
appetite modulation and the release of sex hormones.
• Increased endorphin production is associated with severe injury, prolonged
continuous exercise, stress and consumption of certain foods.
Neurotransmitter-related disorders and their treatment
• Neurotransmitter-related disorders arise from the under- or over-production
of neurotransmitters, or an imbalance in their production.
• Many of the drugs used to treat these disorders are similar to
neurotransmitters.
• Agonists bind to
neurotransmitter.
and
stimulate
receptors,
• Antagonists bind to specific receptors,
neurotransmitter.
thus
mimicking
the
blocking the action of a
• Other drugs inhibit the enzymes which degrade neurotransmitters or inhibit
re-uptake.
Mode of action of recreational drugs
• Many recreational drugs affect neurotransmission in the reward pathway.
• Changes in neurochemistry alter mood, cognition, perception and
behaviour.
• Recreational drugs may:
© H ERIOT-WATT U NIVERSITY
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TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR
Summary Continued
– stimulate the release of neurotransmitters;
– imitate the action of neurotransmitters (agonists);
– block the binding of neurotransmitters to their receptors (antagonists);
– inhibit the re-uptake of neurotransmitters;
– inhibit the enzymatic degradation of neurotransmitters.
Drug addiction, sensitisation and tolerance
• Changes in the number and sensitivity of receptors underlie addiction and
tolerance.
• Sensitisation is an increase in the number and sensitivity of receptors.
• Sensitisation results from exposure to antagonist drugs.
• Sensitisation leads to addiction.
• Desensitisation is a decrease in the number and sensitivity of receptors.
• Desensitisation results from exposure to agonist drugs.
• Desensitisation leads to tolerance.
4.8
Extended response question
The activity which follows presents an extended response question similar to the style
that you will encounter in the examination.
You should have a good understanding of the mode of action of recreational drugs before
attempting the question.
You should give your completed answer to your teacher or tutor for marking, or try to
mark it yourself using the suggested marking scheme.
Extended response question: The mode of action of recreational drugs
15 min
Give an account of the mode of action of recreational drugs (with examples), under the
headings:
A) effects on the brain; (4 marks)
B) modes of action. (6 marks)
..........................................
© H ERIOT-WATT U NIVERSITY
TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR
4.9
107
End of topic test
End of Topic 4 test
Q14: Complete the paragraphs by selecting words from the list. (12 marks)
, which induces the
The reward pathway involves neurons which secrete
particular behaviours. The reward pathway is
feeling of pleasure and so
behaviour.
activated by
stimulate neurons involved in reducing the intensity of pain. Increased levels
.
endorphin production
of endorphins are connected with appetite
is associated with the consumption of certain foods.
used to treat neurotransmitter-related disorders are similar to
Many of the
bind to and stimulate receptors, thus
the
neurotransmitters.
bind to specific receptors, so
the action of a
neurotransmitter.
neurotransmitters,
neurotransmitter. Other drugs inhibit the enzymes which
or inhibit reuptake.
Word list: agonists, antagonists, beneficial, blocking, degrade, dopamine, drugs,
endorphins, increased, mimicking, modulation, reinforces.
..........................................
Q15: Complete the sentences by matching the parts on the left with the parts on the
right. (12 marks)
Many recreational drugs affect neurotransmission in the
perception and
behaviour.
Changes in neurochemistry alter mood, cognition,
reward pathway.
Recreational drugs may stimulate the
agonist drugs.
Recreational drugs may inhibit the
agonists.
Drugs which imitate the action of neurotransmitters are
tolerance.
Drugs which block the binding of neurotransmitters are
release of
neurotransmitters.
An increase in the number and sensitivity of receptors is
re-uptake of
neurotransmitters.
Sensitisation results from exposure to
addiction.
Sensitisation leads to
antagonists.
A decrease in the number and sensitivity of receptors is
sensitisation.
Desensitisation results from exposure to
antagonist drugs.
Desensitisation leads to
desensitisation.
© H ERIOT-WATT U NIVERSITY
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TOPIC 4. NEUROTRANSMITTERS, MOOD AND BEHAVIOUR
..........................................
Q16: Which neurotransmitters are involved in reducing the intensity of pain? (1 mark)
..........................................
Q17: List three factors that increase their production. (3 marks)
..........................................
Q18: Which neurotransmitter is involved in the reward pathway? (1 mark)
..........................................
Q19: What feelings does activation of the reward pathway engender? (1 mark)
..........................................
Q20: What is the difference between agonists and antagonists? (2 marks)
..........................................
Q21: State two other ways that drugs may be used to ameliorate neurotransmitterrelated disorders. (2 marks)
..........................................
Q22: What part of the brain do recreational drugs affect? (1 mark)
..........................................
Q23: What do the changes in neurochemistry caused by recreational drugs alter? (3
marks)
..........................................
Q24: List five ways that recreational drugs exert their effect on neurotransmitters. (5
marks)
..........................................
Q25: What causes drug sensitisation?(1 mark)
..........................................
Q26: What type of drug is involved in sensitisation? (1 mark)
..........................................
Q27: What does drug sensitisation lead to? (1 mark)
..........................................
Q28: What causes drug desensitisation? (1 mark)
..........................................
Q29: What type of drug is involved in desensitisation? (1 mark)
..........................................
Q30: What does drug sensitisation lead to? (1 mark)
..........................................
© H ERIOT-WATT U NIVERSITY
109
Topic 5
Infant attachment and the effect of
communication
Contents
5.1 Introduction . . . . . . . . . . . .
5.2 Forms of infant attachment . . .
5.2.1 Infant attachment . . . . .
5.2.2 Imprinting . . . . . . . . .
5.2.3 Social compensation . . .
5.3 Long period of dependency . . .
5.3.1 Parental control methods
5.4 The effect of communication . . .
5.4.1 Information transfer . . .
5.5 Non-verbal communication . . .
5.5.1 Infant bonding . . . . . .
5.5.2 Adult . . . . . . . . . . . .
5.6 Verbal communication . . . . . .
5.6.1 Language differences . .
5.6.2 Acquiring language . . .
5.6.3 Development of language
5.6.4 Mathematical notation . .
5.7 Learning points . . . . . . . . . .
5.8 Extended response question . .
5.9 End of topic test . . . . . . . . .
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110
112
112
113
116
117
118
119
119
120
120
121
123
123
124
124
126
127
128
128
Learning Objectives
By the end of this topic, you should be able to:
• explain that behaviour is influenced by the inter-related factors of inheritance,
maturation and experience;
• explain the development and significance of infant attachment;
• describe forms of non-verbal communication and explain its role;
• explain the nature and significance of verbal communication through language.
110
TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION
5.1
Introduction
Behaviour is the response of an organism to internal and external stimuli. The nature
of this response is determined by the interaction of three factors: inheritance, maturation
and experience.
Inheritance
Some aspects of the behaviour of all animals are determined by their genes. Those
with a short life history, or, more correctly, short stages in it, simply do not have time
to adapt behaviour as a result of their experience of the environment. Consequently,
their responses to stimuli must be programmed in their genes. For example, the Large
White butterfly, which is common in most of Scotland, has a period of just a few weeks
as an adult in which to find a mate and then locate suitable plants on which to lay its
eggs. Making a mistake would mean that no offspring will be produced, wasting all of
the resources that have gone into getting the animal through the previous stages of its
life cycle. Only genes which induce the appropriate behaviour will pass into the next
generation.
Other insects that live longer as adults do show the ability to learn, albeit within a very
limited context. Honey bee workers, which can live from six weeks to six months as
adults (depending on the time of year), learn to recognise new scents very quickly, an
ability that is obviously related to their task of finding nectar and pollen from whatever
flowers are available at a particular time of the year.
Humans lie at the other end of this spectrum, with a very high proportion of their
behaviour which is developed as a result of experience. Compared to other animals,
we live a long time and spend a greater proportion of our lives as juveniles in the care
of adults. This provides endless opportunities to observe and copy, and to experiment
with alternative responses. Learning to communicate by means of language is a good
example; children usually begin to utter intelligible words and simple sentences during
their second year, and most children can conduct quite complex conversations by the
age of three. This is an ability that our closest Primate relatives, the chimpanzees, do
not possess.
At the simplest level of human behaviour are the reflexes, e.g. knee jerk (assisting
the regaining of balance) or blinking (protecting the eye). These are rapid, automatic,
protective responses that are common to all humans, and many are present from birth.
Some of these are only found in the first few months of life, e.g. the palmar grasp reflex,
by which the baby curls its fingers tightly around any object placed against its palm.
It is now thought that genetics plays a significant role in much more of our behaviour
than was previously imagined, contributing to many of our decisions in life (e.g. choice
of mate).
Maturation
As mentioned in the previous section concerning the structure of the nervous system,
the presence of a myelin sheath greatly increases the rate of impulse transmission by
neurons. In newborn infants, the degree of myelination is relatively low; with the passing
months, more and more neurons develop the myelin sheath, and thus reactions become
much faster. This accounts for the developmental stages observed as infants progress
from sitting, to crawling, standing, and eventually walking. Also, the slow development
of myelination in the hippocampus explains why we do not have memories from our first
© H ERIOT-WATT U NIVERSITY
TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION
two years of life.
The profound physiological changes associated with puberty are likewise expressed
in behaviour. This involves not just the obvious interest in matters sexual, but also
changing tastes. Children generally like sweet things, whereas adults are more likely to
prefer sharper tastes, e.g. mustard or olives.
Environment
If it is accepted that humans depend for the development of a large part of their
behaviour on learning, i.e. changing behaviour in the light of experience, then it follows
that the nature of that experience will influence the behaviour that ensues. Two examples
illustrate this.
1. As mentioned above, children usually start to talk by the age of two, and by three
have quite a complex grasp of their language. Of course, in different countries
and cultures, children learn different languages. If identical twins are separated
at birth as a result of some tragedy, and subsequently reared in different cultures,
they learn different languages. Humans possess a genetically determined ability
to learn language, but the actual tongue that is learned depends on the child's
experience.
2. In the same way, all human cultures have developed music, and all humans have
(to a varied extent, admittedly) the ability to develop musical skills. Most commonly,
that is expressed through song, but could equally be by means of the ability to
play musical instruments, some of which are closely associated with one culture,
e.g. the didgeridoo, which is associated with the Australian Aboriginal people, the
balalaika with Russia, and the bagpipes with Scotland (and Brittany, the Basque
country, and several other places, including parts of England!).
An Estonian bagpiper
© H ERIOT-WATT U NIVERSITY
111
112
TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION
5.2
Forms of infant attachment
Learning Objective
By the end of this section, you should be able to:
• explain that early infant attachment is important in laying the foundation for the
future formation of stable relationships;
• state that attachment becomes evident between six and nine months after birth;
• explain the 'strange situation' procedure;
• describe the responses to the 'strange situation' procedure as secure and
insecure attachment, detachment, anger, and inconsistent responses;
• state that infants who form secure attachments are more likely to investigate
their immediate environment, which helps the development of their cognitive
abilities.
In all mammalian species, the youngster is instantly identified as such. A young wild pig
has a short snout and a striped body with a curly tail, as well as being much smaller than
an adult. A red deer calf has a dappled coat. Somehow, these attributes invite caring in
the parent. Furthermore, they can prevent a big, ugly carnivore which hasn't eaten for
four days from seeing a small relative as a tender meal!
Small, furry animals look cute and evoke feelings of parenting. Thus, there is often
strong bonding between humans and their pets, and between youngsters and cuddly
toys. Is this more apparent in girls than in boys?
If you think of a human child, you think of a head that is greatly out of proportion to the
small limbs, a small nose, large eyes, and a very affectionate personality. These
features have not evolved by accident. Nor have the ways in which a baby
communicates. Crying, clinging and suckling all communicate dependency. A strong,
mutual, emotional attachment develops between the baby and its carers. The mother,
or mother-figure, in particular must be very alert to read these signals from her baby.
The child cannot talk, but is still very active in communicating its needs and desires.
Infant attachment develops, at first indiscriminately, but often becoming specific to one
parent or another at different times during the child's development.
5.2.1
Infant attachment
Infant attachment offers time for a child to observe closely, and to learn. When the child
is facing a parent, it can observe and imitate facial expressions, body language and lip
movements that form words. When facing a third party, the child observes and copies
reactions to these cues.
Thus, a long period of dependency, part of which occurs while the brain continues to
grow, allows opportunities to learn communication, social and language skills in a
protective environment. Informed decisions can be made with the benefit of learning by
means of experience in safe surroundings.
© H ERIOT-WATT U NIVERSITY
TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION
In a series of experiments, conducted between 1963 and 1968, Dr. Harry Harlow
offered young rhesus monkeys a choice between two surrogate 'mothers'. In the first
group, the terrycloth (essentially a cloth toy) mother provided no food while the wire
mother did, in the form of an attached baby bottle containing milk. In the second group,
the terrycloth mother provided food while the wire mother did not. It was found that,
when frightened, the young monkeys clung to the terrycloth mother whether it provided
them with food or not, and that the young monkeys chose the wire surrogate only
when it provided food. Apparently the terrycloth mothers provided something that was
more valuable to the young monkeys than food. She was providing contact comfort.
Harlow's interpretation was that the preference for the terrycloth mother demonstrated
the importance of affection and emotional nurturance in mother-child relationships.
Dr. Harry Harlow's surrogate 'mothers'
5.2.2
Imprinting
It was initially thought that there was one critical period during which a baby had to
imprint onto an adult to securely form an 'infant attachment'. More recent work has
shown that imprinting occurs at several sensitive periods.
It is difficult to investigate infant behaviour for ethical reasons. Researchers use other
animals instead. In fact, information about the sequence of stages in the development
of walking in humans was partly gleaned from experiments on pigeons. Newly fledged
birds were confined in cardboard tubes until their siblings could fly. The restrained birds
could fly at the same time as their peers without having had practice at stretching their
wings at all! One investigation of infant attachment which has been deemed ethical is
the 'strange situation' experiment, which requires video equipment, three adults, a
parent/carer and one subject, an infant child.
© H ERIOT-WATT U NIVERSITY
113
114
TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION
The 'strange situation' is a laboratory procedure which is used to assess infant
attachment that was first developed by Mary Ainsworth, a Canadian developmental
psychologist, in the 1970s. The procedure consists of the following eight episodes:
1. the parent and infant are introduced to the experimental room;
2. the parent and infant are alone - the parent does not participate while the infant
explores;
3. a stranger enters, converses with the parent, then approaches the infant - the
parent leaves, inconspicuously;
4. the 'first separation episode': the stranger's behaviour is geared to that of the
infant;
5. the 'first reunion episode': the parent greets and comforts the infant, then leaves
again;
6. the 'second separation episode': the infant is alone;
7. continuation of the 'second separation episode': the stranger enters and gears
behaviour to that of infant;
8. the 'second reunion episode': the parent enters, greets the infant, and picks up
the infant; the stranger leaves.
Episode 3 of the 'strange situation' procedure
Four aspects of the child's behaviour are observed:
1. the amount of exploration (e.g. playing with new toys) that the child engages in
throughout;
2. the child's reactions to the departure of its parent;
3. stranger anxiety (when the baby is alone with the stranger);
4. the child's reunion behaviour with its parent.
© H ERIOT-WATT U NIVERSITY
TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION
Of these, the last is given most weight in determining the category to which the infant's
behaviour belongs.
The 'strange situation' experiment is carried out on 12 to 18 month old children, who
have reached a level of maturation when they can determine that a stranger is 'foreign'.
The developers of this procedure grouped children into four categories:
1. securely-attached - children play comfortably and are friendly to strangers when
their parent is present, but become distressed in her absence;
2. insecurely-attached, avoidant - children pay little attention to the parent and are
not distressed in her absence; they appear quite detached;
3. insecurely-attached, resistant - children cling to the parent and are distressed in
her absence; they seek reassurance, but reject contact when the parent returns
and can become angry;
4. disorganised attachment - children show inconsistent and contradictory
responses; they may freeze for substantial periods, show very stereotyped or
contradictory behaviour, e.g. they may cry when the parent is away, but then avoid
her on her return and appear to be afraid of her.
Securely-attached children have parents or carers who are attentive, skilled at reading
the child's needs, and promote socialisation. The parents of insecurely-attached
children respond more to their own moods and wishes, ignoring their children's needs.
A disorganised response tends to reflect abnormal parenting, including abuse, and
children with a disorganised response are more prone to psychological disorders.
Alternatively, an early secure attachment tends to have a lasting positive influence,
the children being more likely investigate their environment, helping their cognitive
development.
In today's society, primary carers are often nursery nurses or child-minders. They must
be aware of fulfilling parental wishes whilst ensuring confident progress in their charges.
Imprinting: Question
Q1: Arrange the stages of the 'strange situation' procedure in the correct order.
• Continuation of second separation episode: Stranger enters and gears behaviour
to that of infant.
• First reunion episode: Parent greets and comforts infant, then leaves again.
• First separation episode: Stranger's behaviour is geared to that of infant.
• Parent and infant are alone. Parent does not participate while infant explores.
• Parent and infant are introduced to the experimental room.
• Second reunion episode: Parent enters, greets infant, and picks up infant; stranger
leaves.
• Second separation episode: Infant is alone.
• Stranger enters, converses with parent, then approaches infant. Parent leaves
inconspicuously.
..........................................
© H ERIOT-WATT U NIVERSITY
115
116
TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION
5.2.3
Social compensation
Although children can suffer delays in language learning and in other social skills if
deprived of social contact and stimulation during infancy, they are extremely adept at
compensating for this lack of development. Humans are extremely adaptable and can
recover from setbacks.
Although it is true that infant attachment has an important influence on later
development, local child-rearing customs and the temperament of the child may have
significant bearing on the way in which an infant responds to the 'Strange Situation'
mentioned in the previous section. If a child is used to very close physical contact with
a carer and has little experience of free play or visits by strangers, she will inevitably
respond with concern to a new situation such as this.
We cannot be sure that it is simply early socialisation that gives a child security later in
life. Parents who are responsive to their children's needs in infancy are likely to further
imbue confidence in later years. It is also likely that children can learn social
competence by imitating their peers.
However, other studies have confirmed the value of the initial 'Strange situation'
investigation. In one study, two year old children were shown to have more competence
in the use of tools the more securely attached they had been at an earlier age. They
approached problem solving with enthusiasm and persistence whilst seeking adult help
when required. Insecurely-attached children became frustrated and angry easily. They
refused adult help and gave up trying fairly easily.
In another study, 15-month-old children were rated for infant attachment. They were
then observed at an age of 40 months and their social behaviour was assessed. Those
rated as securely-attached tended to be social leaders and were eager to participate.
Insecurely-attached children tended to be socially withdrawn and hesitant.
© H ERIOT-WATT U NIVERSITY
TOPIC 5. INFANT ATTACHMENT AND THE EFFECT OF COMMUNICATION
5.3
117
Long period of dependency
Learning Objective
By the end of this section, you should be able to:
• state that humans have a relatively long period when they are dependent on
adults;
• explain that the long period of dependency provides opportunities for
socialisation and learning;
• state that different methods of control during a child's development can influence
social competence;
• explain that authoritative control (providing direction) generally results in greater
social competence than authoritarian or permissive control.
A long period of dependency offers opportunities and time for learning.
Large brains are essential for development of the discriminatory skills required to
recognise other animals and learn from observation. Humans require to be adept at
communication because of their complex social structures. However, we do not stay
in the womb long enough for our brains to grow completely. Thus, in a sense, human
babies are born prematurely compared to some mammals, which are much more highly
developed at birth, e.g. horses. We still have lots of maturing to do before we will be
independent, and the long period of dependency required for growth and maturation
offers many opportunities for learning.
The development of increased brain power, the evolution of higher level communication
skills, and the development of large eyes and a complex sensory system are all
interlinked. The need for well-developed senses requires a large brain, but the large
brain would have no function without the developed sensory system. Similarly, the
complex communication skills that developed in tandem require a large brain, but also
drive forward the evolution of such a brain.
An animal that leads a predominantly solitary lifestyle, such as a male otter, has to
learn the basic techniques of hunting and finding suitable habitat from its mother, but
is required to develop relatively little social skill beyond that which is necessary to find
a mate and defend its territory. A social animal, such as a human, must learn all the
subtleties of interaction that allow the individual to effectively interact with its social group
and secure its supply of life's essentials.
The timescale required for development of these skills offers years of opportunities to
integrate into a social structure. The more skills a child develops, the easier it is to
integrate. The average Scot spends the first 25% of their life learning directly from their
parents and other adults. A house mouse, in comparison, is independent of its mother
after three weeks, which might be only 6% of the life-time of a mouse surviving to full
maturity.
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Long period of dependency: Question
Q2:
State and explain two reasons for the long period of dependency in humans.
..........................................
5.3.1
Parental control methods
The methods that parents use to control and guide the behaviour of their children can
be classified under three headings: authoritarian, permissive and authoritative.
The authoritarian parent demands obedience from their children. It should not be
assumed that this is an uncaring approach. Rather, it stems from the parent's belief
that they know what is best for the child and that it is in the child's best interests to
behave as the parent requires. This style tends to also be associated with the use of
punishments for failure in order to reach the required standards, a lack of involvement
of the child in decision-making, and a lack of responsiveness to the child's emotional
needs.
The permissive parent, in complete contrast to the authoritarian one, is reluctant to
impose rules and standards, preferring to let their child regulate its own behaviour.
Again, this is not an uncaring approach, but one based on the philosophy that the
child will develop best if it is allowed to make its own decisions about its behaviour,
reaching decisions based on its own experience and wishes. Punishment is not part
of this regime, but involvement in decision-making and responsiveness to the child's
opinions are paramount. This style is also known as indulgent parenting.
The authoritative parent uses aspects of both of the preceding styles. Standards and
limits are set by the parent, but these are explained to the child, and the child's point of
view is respected and taken into account in decision-making. The authoritative parent
expects maturity and cooperation, offering children lots of emotional support.
A fourth category can also be identified, in which the parent neither sets standards nor
takes the child's views into account, providing no emotional support. This is known as
neglectful parenting.
Research has shown that authoritative parenting is significantly the most successful
approach in terms of developing social competence. Its products (i.e. children) are
likely to have a higher self-esteem and sense of well-being, to enjoy better health and
show less problematic behaviour, and to gain higher academic qualifications. While
this may generally be the case, it is also true that there are significant exceptions, e.g.
the children of certain religious or racial groups, often seen as rather authoritarian, are
disproportionately high academic achievers.
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Parental control methods: Questions
Q3: Complete the table, which shows the combinations of behaviour characteristic of
different methods of parental control, using the listed terms.
Demanding
Undemanding
Responsive
Unresponsive
Terms: authoritarian, authoritative, neglectful and permissive.
..........................................
Q4: In what ways does authoritative parenting differ from:
i
ii
authoritarian parenting;
permissive parenting?
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5.4
The effect of communication
Non-verbal communication is an important part of parent-infant bonding and in adult
communication.
Communication is simply an exchange of information. It occurs among all animals, and,
in some cases, warning calls used by one species (e.g. monkeys) which are specific to
one particular danger, such as a snake or an eagle, are recognisable as such by other
species. Communication does not always require a vocabulary of words.
5.4.1
Information transfer
Information can be passed both intentionally and unintentionally by verbal and nonverbal language. Non-verbal communication consists of body language which is often
unconscious, including grimaces and other facial movements, and gestures, which are
often under conscious control.
When a baby smiles at her mother, a boy mirrors his girlfriend's posture or your eyes
light up when the teacher enters the room, non-verbal communication is taking place.
Friendship and intimacy are often signalled as much by non-verbal clues as by the
content and context of conversation. Eye contact lasts longer, proximity is closer, and
may include touching, and smiling is more frequent when we are with close allies.
We must be careful as we may often read non-verbal communication according to our
own moods or needs rather than those intended by the author. In addition, a skilled
practitioner, not always a magician by trade, can easily mis-communicate information
by redirecting an observer's gaze or by giving a false sense of security using
non-verbal language.
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Information transfer: Question
Q5:
Put the communication methods listed into the correct categories in the table:
Non-verbal Body language
Verbal
Non-verbal Gesture
Communication methods: feeling your collar when under pressure; indicating that an
archer's bow finger will be cut off if he gets caught; pointing to your nose when playing
charades; shouting out; showing whites of eyes when angry; sobbing loudly; talking;
throwing a fist in the air; walking with an expanded chest after a victory.
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5.5
Non-verbal communication
Learning Objective
By the end of this section, you should be able to:
• explain how non-verbal communication contributes to the formation of
relationships between individuals;
• state that non-verbal communication can signal attitudes and emotions;
• state that non-verbal communication acts as an aid to verbal communication.
This section is divided into sub-sections about communication in infants and then in
adults.
5.5.1
Infant bonding
During the growth of relationships, bonding occurs when a child smiles at a parent, or
when a couple mirror one another's expressions or posture. This establishes strong
emotional ties. Protective feelings are promoted and these behaviours have a survival
value for the participant. Positive feedback ensues and so a child cooing at her parent
will elicit further caring responses.
When a parent responds by smiling, vocalising (often in a high-pitched, sing-song voice
which is encouraging to the child) and handling the infant, the child will respond in
similar fashion. From around four months, the infant recognises and prefers familiar
faces and responds more to these than to others.
Facial expressions are much more important to apes, and especially to ourselves, than
to other species. Whereas other animals walk side to side to size one another up,
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humans observe facial expressions with concentration. This is particularly important in
infants and in adolescents, perhaps explaining why a tiny facial spot can cause such
panic in a teenager's heart!
This is because we communicate so much by our facial expressions, and by lip and
tongue movements. We observe speech at the same time as listening to it. 'Read my
lips' sounds trite, but is rife with meaning.
5.5.2
Adult
In adults, non-verbal communication remains of huge importance. Even seemingly
meaningless noises convey information about emotions and attitudes. Speech sounds
such as "och" and "d'oh" in variants of the English language, or "ben" and "boff" in
French, inform the observant listener. These sounds and inflections of the voice are
sometimes referred to as para-language. Voice inflections are particularly crucial in
languages, such as Chinese, where one word can have several meanings, depending
on inflection and pitch.
Shifting eyebrows, nodding, lack of eye contact, tears, and even sweating offer positive
or negative feedback during a conversation, providing information which should not be
ignored, neither by the speaker nor by the listener.
Body language and gestures, such as verbal language, are culturally rooted. As
previously mentioned, cultures vary across distances and across time. Beware! A
gesture deemed friendly in your culture may be extremely aggressive or insulting in
another.
Sometimes, as adults, we have to repress our natural communication skills. A parent
will often try to convey a feeling of well-being to children even though she, herself, is
concerned about something.
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Facial expressions
..........................................
Body language across the world
Web sites about body language across the world
20 min
Access the websites listed below to compare how body language differs across the
world.
• http://www.everythingesl.net/inservices/body language.php: compares cultures;
• http://www.ai.mit.edu/projects/sociable/facial-expression.html: a robot that makes
faces;
• http://italian.about.com/library/weekly/aa062001a.htm: speaking Italian with your
hands.
..........................................
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5.6
Verbal communication
123
Learning Objective
By the end of this section, you should be able to:
• state that language uses symbols to represent information;
• explain that language enables information to be organised into categories and
hierarchies;
• state that this organisation of information accelerates learning and intellectual
development;
• explain that the ability of humans to communicate verbally has resulted in the
transmission of knowledge, development of culture and social evolution.
Humans differ from all other species in the complexity of their spoken language and in
their ability to use verbal language, i.e. words and sentences rather than just sounds,
whether written or spoken. In contrast to the vagueness of some body language, verbal
language transmits complex information in a clear, concise and unambiguous manner.
In addition, dialogue, in the form of questions and answers, can supplement and clarify
communication.
Rules for combinations of symbols or words developed. These are known as syntax.
These rules vary from culture to culture and evolve with usage through time. The
history of associated cultures can be clearly observed in the similarities between one
language and another. For example, French, Spanish, Romanian and English all seem
to be derived from Latin.
5.6.1
Language differences
Differences also occur between language used in school (by the establishment) and
the language of the playground. Knowledge of the patois gives a quick reference point
defining age, interests and position in the local hierarchy.
Syntax provides a framework which allows language to be constructed from phrases
encoded in memory. Nouns, verbs, adverbs, adjectives and phrases each have sense
in their own right. They can then be combined in a variety of ways to give sentences
which have meanings of their own. This is known as semantics. To create language,
thoughts that are represented by words are built into phrases which form sentences.
These are governed by rules of syntax, which an infant has to somehow internalise
while simultaneously growing a nervous system! A child has an enormous capacity to
acquire vocabulary and to glean the rules of syntax and grammar. By the age of six, a
child typically has a vocabulary of some 15,000 words. Learning the rules of semantics
takes rather longer...
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Consider the situation where a teacher describes your project as being "outstanding
work".
Ambiguity of language - which is it?
5.6.2
Acquiring language
The website http://www.pnas.org/cgi/content/full/98/23/12874 gives an interesting
insight into the problems faced by infants in acquiring language and the success that
they have from the age of around seven months in overcoming them.
As we grow older, the number of facts that require to be memorised rises exponentially.
Our brains compensate by using language rules to construct hierarchies of
understanding. Using complex language allows us to learn and develop intellectually.
We can aid our brains by putting burdens on the mind. By creating hierarchies as you
memorise your work you will assist your brain in encoding, storing and retrieving
information.
5.6.3
Development of language
The symbols used to construct spoken language can be converted to written symbols.
At some pre-historic time, man began to record debts and harvests as a series of
symbols; perhaps in order that feudal lords, who did not live close enough to oversee
their vassals in a rapidly-expanding population, could keep track of their dues. Using
different symbols, or hieroglyphics, in different cultures, written language developed in
the same way that a variety of spoken symbols evolved to represent the same items in
different geographical areas. This development would inevitably have a consequential
effect on spoken language because both were required to become more precise about
chattels and populations.
Greek letters
Chinese symbols for love
α,
β,
γ,
δ,
. . . Δ,
Σ,
Ω
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The Rosetta Stone which, with text in Ancient Egyptian, and translations into Demotic
and Greek, first enabled the Egyptian hieroglyphs to be interpreted
Who is 'in' and who is 'out' of your crowd?
Navigate to the following website: http://www.ruf.rice.edu/~kemmer/Words/shibboleth.html
Words and pronunciations let us know who is 'in' and who is 'out' of our crowd. Make a
list of words that describe what is important in your local sub-culture.
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..........................................
5.6.4
Mathematical notation
Many centuries ago, Chinese and Greek scholars developed mathematical notation,
such as algebraic symbols, as a special type of language. Language had already proved
its worth as a means of codifying information. Symbols allow organisation of information
into categories and hierarchies.
Mathematical
symbols
≡,
, ⊥ , ∝, =, ∠, ≈, ∞, ±
Logic symbols
in electronic
circuits
Language developed as a form of communication between people who were present
simultaneously. Crucially, we can now communicate verbally when we are apart and
leave messages for later. We can also leave written messages for later. We can form
images using cameras to be stored or transmitted.
With the development of logarithms and calculators, codification of language went even
further, allowing the development of computers, originally called 'difference engines',
cell phones, mp3 players and many other gadgets that we now take for granted.
Mathematical notation: Further reading
Go
to
http://www.macs.hw.ac.uk/~greg/calculators/napier/great.html
http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Babbage.html to
about the contributions of John Napier and Charles Babbage to this revolution.
and
read
..........................................
Verbal communication: Further reading
10 min
You may wish to compare communication among chimpanzees with communication
by humans which you can do so by investiagating the following website:
http://www.janegoodall.org/chimpanzees/communication
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5.7
Learning points
Summary
Forms of infant attachment
• Early infant attachment is important in laying the foundation for the future
formation of stable relationships.
• Attachment becomes evident between six and nine months after birth.
• Explain the 'strange situation' procedure.
• Describe the responses to the 'strange situation' procedure as: secure and
insecure attachment, detachment, anger, and inconsistent responses.
• Infants who form secure attachments are more likely to investigate their
immediate environment, which helps the development of their cognitive
abilities.
Long period of dependency
• Humans have a relatively long period when they are dependent on adults.
• The long period of dependency provides opportunities for socialisation and
learning.
• Different methods of control during a child's development can influence
social competence.
• Authoritative control (providing direction) generally results in greater social
competence than authoritarian or permissive control.
Non-verbal communication
• Non-verbal communication contributes to the formation of relationships
between individuals.
• Non-verbal communication can signal attitudes and emotions.
• Non-verbal communication acts as an aid to verbal communication.
Verbal communication
• Language uses symbols to represent information.
• Language enables information to be organised into categories and
hierarchies.
• This organisation of information accelerates learning and intellectual
development.
• The ability of humans to communicate verbally has resulted in the
transmission of knowledge, development of culture and social evolution.
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5.8
Extended response question
The activity which follows presents an extended response question similar to the style
that you will encounter in the examination.
You should have a good understanding of human communication before attempting the
question.
You should give your completed answer to your teacher or tutor for marking, or try to
mark it yourself using the suggested marking scheme.
Extended response question: Human communication
Describe ways in which humans communicate under the headings:
15 min
A) non-verbal communication; (4 marks)
B) verbal communication. (6 marks)
..........................................
5.9
End of topic test
End of Topic 5 test
Q6: Complete the sentences by matching the parts on the left with the parts on the
right. (8 marks)
Early infant attachment is important for
investigate their
environment.
Attachment becomes evident between
different methods of
control.
Two responses to the strange situation experiment are
dependent on adults.
Infants who form secure attachments are more likely
to
greater social
competence.
Humans have a relatively long period when they are
six and nine months after
birth.
The long period of dependency provides opportunities
for
detachment and anger.
Social competence can be influenced by
future stable relationships.
Authoritative control generally results in
socialisation and learning.
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..........................................
Q7: Complete the paragraphs by selecting words from the list. (10 marks)
Non-verbal communication contributes to the
of relationships between
and emotions, and acts as an
to verbal
individuals. It can signal
communication.
Language uses
to represent
and enables information to be
and hierarchies. This organisation of information accelerates
organised into
and
development. The ability of humans to communicate verbally
, development of
, and social
has resulted in the transmission of
evolution.
Word list: aid, attitudes, categories, culture, formation, information, intellectual,
knowledge, learning, symbols.
..........................................
The following four questions refer to infant attachment the 'strange situation' procedure.
Q8: Which people would be involved in the procedure other than an infant and a
parent/carer? (2 marks)
..........................................
Q9: Which observation is most significant in deciding the category to which the infant
belongs? (1 mark)
..........................................
Q10: Which group of infants are not distressed by the parent/carer's absence? (1 mark)
a)
b)
c)
d)
Securely attached
Insecurely attached, avoidant
Insecurely attached, resistant
Disorganised attachment
..........................................
Q11: Which type of response is most likely to develop the infant's cognitive abilities? (1
mark)
a)
b)
c)
d)
Securely attached
Insecurely attached, avoidant
Insecurely attached, resistant
Disorganised attachment
..........................................
Q12: When does infant attachment first become evident? (1 mark)
..........................................
Q13: State two aspects of an infant's development for which the human's long period of
dependency provides opportunities. (1 mark)
..........................................
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Q14: Which type of parental control results in the greatest social competence? (1 mark)
a)
b)
c)
d)
Authoritative
Authoritarian
Neglectful
Permissive
..........................................
Q15: What are the characteristics of neglectful parenting? (2 marks)
..........................................
Q16: What can be signalled by non-verbal communication? (1 mark)
..........................................
Q17: How does language represent information? (1 mark)
..........................................
Q18: Into what does language enable information to be organised? (1 mark)
..........................................
Q19: List two advantages of this organisation of information. (1 mark)
..........................................
Q20: State two key characteristics of humans that are facilitated by language. (2 marks)
..........................................
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Topic 6
The effect of experience and social
influences
Contents
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.2 The effect of practice on motor skills . . . . . . . . . . . . . . . . . . . . . . . .
132
132
6.3 Imitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
133
6.3.1 Monkey see, monkey do! . . . . . . . . . . . . . . . . . . . . . . . . . .
6.4 Trial and error learning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
134
135
6.5 Generalisation and discrimination . . . . . . . . . . . . . . . . . . . . . . . . . .
6.6 Social facilitation and deindividuation . . . . . . . . . . . . . . . . . . . . . . . .
137
139
6.7 Influences that change beliefs . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.8 Learning points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
141
142
6.9 Extended response question . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.10 End of topic test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
143
143
Learning Objectives
By the end of this topic, you should be able to:
• define the term 'learning';
• explain why practice improves motor skills;
• describe the role of imitation in learning;
• explain how learning can be improved by means of reinforcement, shaping,
extinction, and trial and error;
• describe the processes of generalisation and discrimination.
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6.1
Introduction
Like nearly all Primates, humans are social animals, i.e. they live in groups rather
than on their own. These groups consist of closely related individuals belonging to
several generations. The social changes brought about by industrial and agricultural
development have disrupted these groups, but it is only a few generations ago that they
were the units around which our society was structured, e.g. the clans of the Highlands
and the Borders.
In such a social structure, the children live throughout their dependent years in close
proximity to adults at home and at work, and this provides abundant opportunities to
observe and copy behaviour, and to experiment within the sheltered confines of the
group. Furthermore, it allows the adults to supervise the young, applauding good
behaviour and discouraging bad. By the time a person has reached the status of
adult, they will have been thoroughly versed in the ways of their tribe and their local
environment, and in the skills necessary to survive in both. Principal among these skills
is the ability to learn, i.e. to change behaviour in the light of experience.
6.2
The effect of practice on motor skills
Learning Objective
By the end of this section, you should be able to:
• state that learning is a change in behaviour brought about by experience;
• explain that motor skills are improved by repeated practice;
• state that practice of a motor skill establishes a motor pathway in the brain.
Learning can be defined simply as a change in behaviour as a result of experience. In
other words, if you start climbing a set of stairs on a different side to normal as a result
of standing on a squeaky floor-board, you have learned. Changing behaviour underlies
all teaching and learning.
Motor skills are sequences of movements that are necessary to perform a particular
task. An apparently simple action, such as picking up a pencil, belies the complexity
of the neural activity which enables it to be carried out smoothly and without conscious
thought. There is the sensory input that is required to recognise the pencil amongst its
surroundings, and to judge its position relative to the hand. Then there is the activity of
the motor cortex of the brain to initiate the necessary muscular contractions to move the
arms and fingers, and the action of the cerebellum to co-ordinate the contractions and
relaxations of these muscles to give the fine motor control involved in precisely closing
the fingers around the pencil. Easy, but definitely not simple!
Learning motor skills from a book is very ineffective. Even with diagrams and pictures,
it is still very hard to make the right movements. On the other hand, observing someone else perform the task and then copying them works very well. Although we usually
don't get things right straight away, repeated demonstration quickly corrects mistakes.
This establishes the movements that must be produced, but to be able to reproduce
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them reliably requires the establishment of a motor pathway linking all the parts of the
nervous system, which must work together to make the movement possible. That can
only be done by repetition.
This is why professional golfers spend hundreds of hours working on a new swing,
or professional tennis players practice serve after serve for hours on end. They are
'grooving in' the movements so that they automatically perform them correctly in a match
situation. Indeed, if things go wrong and they have to start thinking about it, their game
can fall apart.
These principles apply to mere mortals as well. If you want to play guitar better, or cast
a fishing fly more accurately, there is only one route to success - practice, practice,
practice... It is said that to learn a folk tune, you have to play it faultlessly eighty
times, and that to become competent on an instrument takes 10,000 hours of practice.
Fortunately, correctly managed, the learning process itself can be enjoyable, and the
sense of achievement as progress is made is a reward in itself.
The effect of practice on motor skills: Questions
Q1: What is meant by the term 'learning'?
..........................................
Q2: What must be established to learn a motor skill?
..........................................
Q3: What is meant by practising a motor skill?
..........................................
6.3
Imitation
Learning Objective
By the end of this section, you should be able to:
• explain that a great deal of human behaviour is learned by observing and
imitating the behaviour of others.
As mentioned in the previous section, imitation is a very effective method of learning
certain types of skill. The apparent simplicity of the activity once more masks the
considerable underlying complexity of the actions that take place in the nervous system.
Once the other person's actions are observed (seen or heard), somehow the brain
co-ordinates the activity of the appropriate muscles to produce the same activity.
The underlying neurological processes seem to be very complex and, as yet, little
understood, although certain cells in the motor cortex may be involved which are known
as mirror neurons. These fire impulses when an activity is the same as that observed in
another person.
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However it may come about, imitation is the mechanism by which a great deal of
basic human behaviour is learned, whether it be how to use a knife and fork, or how
to behave towards our children. The importance of parents as role models for their
children is obvious and well-known. Much of this, such as gender stereotyping, is
wholly unconscious learning, and only becomes apparent in our actions and responses
to particular situations.
6.3.1
Monkey see, monkey do!
Researchers have recently demonstrated that monkeys 'imitate with a purpose', copying
behaviour as a form of social learning. Such mimicry had previously been established
only in great apes, including humans and chimps, but now Italian researchers have
recorded the phenomenon in newborn rhesus macaques.
Most of us have delighted in very young relatives mimicking our facial expressions.
This 'imitation period' lasts up to three months in human infants. Newborns rely on
watching adults to learn facial expressions, and mimicry is thought to be crucial in the
successful development of parent-infant relationships.
It is thought that specific brain cells, called 'mirror neurons', fire in a human infant when
it watches an adult expression and copies it. Similar mirror neurons are active during
brain scans when rhesus monkeys watch another animal perform an action, and also
when they copy that action. This similarity suggests a common brain pathway in
humans and monkeys.
A newborn macaque (less than 10 days old) imitates tongue protrusion by a human
(Evolution of Neonatal Imitation. Gross L, PLoS Biology Vol. 4/9/2006, e311
doi:10.1371/journal.pbio.0040311)
Pier Ferrari at the University of Parma, Italy, and colleagues, tested 21 newborn
macaques by holding each in front of a researcher who made various facial
expressions as illustrated above.
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None of the infants showed any imitation at one day old. By day three, infants started to
copy the researchers' expressions, including sticking their tongues out, opening their
mouths on cue, and smacking their lips. These are all expressions that are typical of
normal macaque behaviour. Watch footage of macaques copying tongue poking and
mouth opening in the video at the end of this topic.
Although it is possible that macaques may copy other macaques for longer in the wild,
imitation of researchers had ceased by the age of two weeks. It seems that the
capacity for imitation evolved earlier in primate evolution than previously thought, and
definitely before the rhesus monkey ancestor split from the human line of descent,
about 25 million years ago.
6.4
Trial and error learning
Learning Objective
By the end of this section, you should be able to:
• explain that behaviour patterns which have positive consequences for the
individual are likely to be repeated;
• state that positive outcomes reinforce a behaviour;
• state that behaviours which are not rewarded by positive outcomes, or have
negative outcomes, will disappear;
• state that a behaviour which is extinguished is said to be extinct;
• explain shaping as rewarding behaviour that successively approximates to the
desired behaviour.
Trial and error
Even more than other mammals, humans are inquisitive creatures. They are constantly
exploring, whether it be new continents or new foods, and they are always asking
questions of their environment. Equally, especially in our youth, we are prone to
challenge the ways in which things are done and to try alternatives. This behaviour
is what has brought us from the Stone Age to the Computer Age within the span of only
some 400 generations in Britain.
How many of us start pressing buttons without consulting the manual when taking a new
electronic gadget out of its packaging? In doing this, we are using one of the simplest
of our learning techniques, called Trial and Error. We try something to see whether it
works; if it has a desired outcome, that reinforces the behaviour and we are likely to
repeat it. If it has no effect, or worse still, results in an undesirable outcome, then the
behaviour of pressing that button will not be repeated; it will become extinct.
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Reinforcement
The process of training and teaching seeks to reinforce positive outcomes and
extinguish negative ones. Rewarding desirable behaviour is a very effective method
of reinforcing it. When a puppy lies down on command, you show your pleasure by your
tone of voice and the treat that you give it. This is a reward for the puppy, and it is more
likely to repeat the behaviour when the command is given again. Alternatively, jumping
up with muddy paws to greet people is a behaviour of a puppy that we would want to
extinguish. This can either be done by ignoring it, or by showing displeasure in your
tone of voice.
Providing a reward is positive reinforcement, whereas something removed or avoided
acts as negative reinforcement. A good example of negative reinforcement is putting up
an umbrella when the rain starts. This is classed as negative in that it is the removal of
the stimulus of the rain on the head which reinforces the behaviour. Another example
would be donning earphones when the next-door neighbour starts playing his banjo.
Negative reinforcement is frequently confused with punishment. Whereas showing
disapproval often works very effectively towards extinguishing a behaviour, e.g. the
word "No!" exclaimed very firmly, physical punishment usually has outcomes which are
not intended. A puppy that is struck learns to fear the person who hits it rather than to
keep its paws on the floor.
It is also worth pointing out that the reward, or indeed the punishment, must have
meaning for the subject. You are unlikely to reinforce desired behaviour in a young
child by offering her dark chocolate, or depriving her of the chance to watch the news
on the television.
Shaping
Shaping is rather more than the rewarding of behaviour that approximates to that
desired. More correctly, it is the differential reinforcement of successive approximations
to a desired behaviour. It was first identified by the American psychologist and
behaviourist B. F. Skinner who initially worked with pigeons, even developing a pigeonguided missile for the US navy in World War II. His later analyses of teaching and
learning processes were, and still are, enormously influential.
Although its definition sounds very complex, shaping is, in fact, very simple and used
all the time in training and teaching situations. Anyone who has had to endure the
initial stages of a relative learning to play a musical instrument will be familiar with the
screeches and wails of their early efforts. Yet, these same excruciating sounds will elicit
high praise from the teacher, for the pupil has actually managed to make a sound with
the instrument. Soon though, only more melodious efforts will lead to praise. Thus,
the instructor keeps raising the bar for the pupil, demanding more achievement each
time before the reward of praise is forthcoming. Think of your own efforts at learning to
pronounce words in a foreign language and how they were dealt with by your teacher.
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137
Trial and error learning: Question
Q4: Complete the sentences by matching the parts on the left with the parts on the
right.
Trial and error
becomes extinguished.
Extinct behaviour
involves differential reinforcement of successive
approximations to a desired behaviour.
Reinforcement
involves random responses to a stimulus.
Shaping
6.5
involves making similar response to a stimulus more
likely on subsequent occasions.
..........................................
Generalisation and discrimination
Learning Objective
By the end of this section, you should be able to:
• explain that generalisation is the process by which a response learned to in
reaction to one stimulus is evoked by a different, but similar, stimulus;
• explain that discrimination is the process by which people learn to make different
responses to different, but similar, stimuli.
Generalisation and discrimination are vital parts of our learning skills in that they allow
us to develop fundamental responses to aspects of our environment.
Generalisation
How often do you hear someone declaring that they don't like fish or green vegetables,
probably as a result of an encounter with a particularly poorly cooked example early in
life? While these are trivial examples (although not to the anguished grandparent who
sees a carefully prepared meal refused), learning to avoid snakes or stripy flying insects
are not. Generalisation involves identifying some key, common feature of objects which
allows us to group them together despite their being different in other respects.
The classic example is the child who generalises the response to being bitten by a dog
once to a fear of all dogs. In practice, the opposite situation is more dangerous: a child
who is accustomed to running up to pat a friendly dog is in much more danger if she
generalises this to assume that all the dogs she meets will be friendly.
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Discrimination
The process of discrimination involves the identification of key features of an object
that will allow us to distinguish it from other similar objects.
Chanterelles are very tasty golden-yellow fungi which grow quite widely in Scottish
woods. Unfortunately, there are some seriously poisonous species with which they can
be confused. It is essential to know the precise characteristics which differentiate it from
other yellow fungi found on the forest floor if a truly mouth-watering omelette is to be
confidently enjoyed.
Many tourists visiting the Highlands go home happy that they have spotted Golden
Eagles soaring over the glens, when in fact they have seen the similar, but far more
common, buzzard. As with the Chanterelle, once the real thing has been seen, it is
unlikely that there will be further confusion because the key features of the organism are
recognised.
Again, the classic example involves dogs. A postman who has been given a little nip by
a Jack Russell terrier will be very wary of this breed even though he may cheerily greet
much larger dogs such as Labradors.
Generalisation and discrimination: Question
Q5:
Complete the table by placing the activities in the correct column.
Generalisation
Discrimination
Activities:
• Catching the No. 54 bus at the bus station
• Checking the tomatoes in the supermarket before putting them in the bag.
• Enjoying travelling by train.
• Midges spoil camping holidays in Britain.
• Not liking the people from a particular city.
• Only eating the sweets in the purple wrappers.
• Picking the spotted puppy from the litter.
• Randomly choosing any dish on the menu.
..........................................
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TOPIC 6. THE EFFECT OF EXPERIENCE AND SOCIAL INFLUENCES
6.6
Social facilitation and deindividuation
139
Learning Objective
By the end of this section, you should be able to:
• explain that the performance of a task may be improved in the presence of
others;
• state that the presence of others in a competitive situation may enhance
performance;
• state that the presence of an audience may improve performance;
• state that deindividuation is responsible for the loss of identity in a crowd;
• explain that deindividuation leads to diminished restraints on behaviour;
• state that deindividuation leads to behaviour which would not be shown by
individuals on their own.
This topic considers the positive and, sometimes, negative effects that the presence of
other people can have.
Social facilitation
The presence of other people can have a marked effect on our performance of a task.
This is known as social facilitation. Sometimes, this effect can have a positive influence,
e.g. when playing a team sport, most of us will endeavour to improve our performance
for the good of the team.
This is called the co-actor effect: increased performance in competitive situations. When
a group of cyclists were timed on their own, against the clock, they did much worse than
when cycling in groups. This effect is present even in situations which would not normally
be seen as competitive. For example, car drivers take 15% longer to travel the first 100
metres after drawing away from a green light if there is no other car in the next lane.
A second kind of social facilitation operates when performing in front of an audience:
the audience effect. When people talk about a home advantage in sporting events, it is
the effect of the home crowd inspiring their team that is involved. If a team is required to
play a fixture in an empty stadium, it very seldom results in an entertaining game. In the
2012 London Olympics, many of the British medal winners cited the crowds as a major
contributor to their success.
On the other hand, some research has shown, and you may empathise with this, that
the presence of others can impair performance. This gives a clue as to how social
facilitation can operate. A certain level of arousal of the nervous system will lead to
improved performance. After this, further arousal will cause distress.
Arousal seems to help when we feel in control of a situation. When performing a task
which is well within our capabilities, social pressure improves performance, but, when
the task is unfamiliar, we perform below par. In one study, expert pool players who potted
71% of their shots when practising alone made 80% of the shots with an audience of
four people. As you would expect, poor players who made only 36% of their shots when
unobserved, collapsed to just 25% when observed. This explains why confidence is so
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TOPIC 6. THE EFFECT OF EXPERIENCE AND SOCIAL INFLUENCES
important when performing. If confidence is high, social facilitation makes us do well
and vice versa.
Deindividuation
Anyone who has attended a big club football match will be aware that the behaviour
of some of the crowd can be quite surprising if you are not used to it. The chanting,
swearing, and gesturing towards opposition players and supporters, and of course the
referee, would quickly lead to a person being arrested if it was to be repeated in the
local High Street. And yet, these same people, when dispersed from the stadium, do
not behave in this way - it is, in fact, quite atypical of them. Also, it is more than just
believing that in a mob you are less likely to be caught and that, therefore, you can take
greater risks than usual.
This effect has a name: de-individuation. It is defined as the loss of personal identity
in groups, leading to diminished restraints on behaviour. When we become a member
of a group, we somehow submerge our own personality into a group identity. There is
diminished restraint, and anti-social behaviour can occur. This same effect can influence
individuals in groups outside the confines of a football stadium, where it can lead to
vandalism, looting and rioting as it did in London and other English cities in the summer
of 2011.
A classic experiment that demonstrates this behaviour involved giving students various
problems, alone or in groups. If shown a line and asked to compare it with several other
lines for length, solo students performed very well. However, when invited to perform the
same task along with three or four 'plants' who were primed to give obviously incorrect
answers, the subjects doubted themselves to the extent that they joined in with the group
behaviour and gave answers that they clearly knew were wrong.
Similarly, in another classic experiment, students who had been invited to administer
electric shocks to other students in a room next door would keep turning up the voltage
when instructed by their supervisor, who would urge them to continue even when they
raised objections. No shocks were actually administered, of course, although the subject
heard the wails of an actor in mock pain, which increased with the severity of the voltage
'applied'. They were prepared to over-ride their own reservations about their actions
when they were in conflict with orders from an authority figure, even though they were
aware of the apparent effect of their actions. This is known as the Milgram experiment.
In fact, participation in this experiment had quite disturbing effects on the students. Its
origin was the defence given by soldiers on trial for committing atrocities during World
War II that "they were only following orders".
Social facilitation and deindividuation: Question
Q6:
Match the phrases on the left with the words on the right.
Performance improved by the presence of others:
deindividuation.
Performance improved in front of a crowd:
co-actor effect.
Performance improved by having competition:
audience effect.
Loss of identity in a crowd:
social facilitation.
..........................................
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TOPIC 6. THE EFFECT OF EXPERIENCE AND SOCIAL INFLUENCES
6.7
141
Influences that change beliefs
Learning Objective
By the end of this section, you should be able to:
• explain that internalisation is the changing of one's beliefs as a result of
persuasion;
• explain that identification is the changing of one's beliefs to those of an admired
influencing source.
Internalisation
We have defined behaviour as our range of responses to stimuli in our environment,
and to other humans who form part of that environment. During our interactions with
others we frequently seek to change their views, and they try to change ours. Our
usual approach is to attempt to persuade our audience to share our view by presenting
them with convincing evidence. You may, or may not, be impressed by the argument
that "my team has won ten games this season and yours has only won five, so we are
twice as good as you", but similar versions are heard all the time.
This approach to changing beliefs is called internalisation. It is used frequently by the
advertising industry, e.g. "Nine out of ten cats interviewed said they preferred Purr-fect
Cat Food". A more convincing use of the technique is found in the 502 pages of evidence
presented by Charles Darwin in his seminal book "On the origin of species by means of
natural selection".
Identification
Advertisers also utilise another approach to changing behaviour. They have worked
out that humans are social animals and prefer to have group membership. Individuals
try to have a high status in groups because this confers all sorts of benefits, such
as preferential access to food and mates. One way in which to gain this status is to
impress the group by being identified with famous people. Consequently, sponsors pay
large sums of money to entice iconic figures to endorse their products. Advertisements
often feature well-known celebrity figures from sport, film or TV, associating them with
products, e.g. after-shave or shampoo.
The rationale of this technique is that people will want to be linked to a star, purchasing
a product to be like them. This is known as identification and is defined as the changing
of one's beliefs to those of an admired influencing source.
Influences that change beliefs: TV adverts
The next time that you watch a commercial TV station, try to decide which technique is
being used by each advertisement.
Various techniques are used, sometimes at the same time, so you might like to make
up a table headed with the different approaches that you have identified, and note the
products that are being sold under each heading.
..........................................
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6.8
Learning points
Summary
The effect of practice on motor skills
• Learning is a change in behaviour brought about by experience.
• Motor skills are improved by repeated practice.
• Practice of a motor skill establishes a motor pathway in the brain.
Imitation
• A great deal of human behaviour is learned by observing and imitating the
behaviour of others.
Trial and error learning
• Behaviour patterns that have positive consequences for the individual are
likely to be repeated.
• Positive outcomes reinforce a behaviour.
• Behaviours that are not rewarded by positive outcomes, or have negative
outcomes, will disappear.
• A behaviour that is extinguished is said to be extinct.
• Shaping is rewarding behaviour that successively approximates to the
desired behaviour.
Generalisation and discrimination
• Generalisation is the process by which a response learned in response to
one stimulus is evoked by a different, but similar, stimulus.
• Discrimination is the process by which people learn to make different
responses to different, but similar, stimuli.
Social Facilitation and deindividuation
• Performance of a task may be improved in the presence of others.
• The presence of others in a competitive situation may enhance
performance.
• The presence of an audience may improve performance.
• Deindividuation is responsible for the loss of identity in a crowd.
• Deindividuation leads to diminished restraints on behaviour.
• Deindividuation leads to behaviour which would not be shown by individuals
on their own.
Influences that change beliefs
• Internalisation is the changing of one's beliefs as a result of persuasion.
• Identification is the changing of one's beliefs to those of an admired
influencing source.
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TOPIC 6. THE EFFECT OF EXPERIENCE AND SOCIAL INFLUENCES
6.9
143
Extended response question
The activity which follows presents an extended response question similar to the style
that you will encounter in the examination.
You should have a good understanding of group behaviour and social influence before
attempting the question.
You should give your completed answer to your teacher or tutor for marking, or try to
mark it yourself using the suggested marking scheme.
Extended response question: Group behaviour and social influence
Give an account of group behaviour and social influence under the headings:
15 min
A) social facilitation; (3 marks)
B) deindividuation; (4 marks)
C) influences that change beliefs. (4 marks)
..........................................
6.10
End of topic test
End of Topic 6 test
Q7: Complete the sentences by matching the parts on the left with the parts on the
right. (9 marks)
A change in behaviour brought about by experience:
shaping.
An important part of learning:
imitation.
Improved by repeated practice:
extinct.
Established by practice of a motor skill:
learning.
Copying behaviour:
reinforcement.
Makes behaviour patterns likely to be repeated:
observing.
Rewarding desired behaviour:
motor skills.
Fate of behaviour that is not rewarded:
motor pathway.
Rewarding behaviour as it gets closer to what is wanted:
positive outcomes.
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TOPIC 6. THE EFFECT OF EXPERIENCE AND SOCIAL INFLUENCES
..........................................
Q8:
Complete the paragraphs by selecting words from the list. (11 marks)
is the process by which a response learned to one stimulus is evoked by
but similar stimulus, whereas
is the process by which people
a
stimuli.
learn to make different responses to
situation may enhance performance, as can the
The presence of others in a
may improve performance. These are examples of different
presence of an
.
is responsible for the loss of identity in a crowd
types of social
on behaviour.
which may lead to diminished
is the changing of beliefs as a result of persuasion.
changing of one's beliefs to those of an admired influencing source.
is the
Word list: audience, competitive, deindividuation, different, discrimination, facilitation,
generalisation, identification, internalisation, restraints, similar.
..........................................
Q9: Explain why certain behaviours are likely to be repeated and others become
extinct. (2 marks)
..........................................
Q10: Describe the process of simple reinforcement. (1 mark)
..........................................
Q11: Describe the process of shaping. (1 mark)
..........................................
Q12: Explain why a child being bitten by a small white dog might lead to discrimination.
(1 mark)
..........................................
Q13: Explain why a child being bitten by a small white dog might lead to generalisation.
(1 mark)
..........................................
Q14: Suggest why athletes almost invariably achieve their best performances in big
competitions. (2 marks)
..........................................
Q15: Advertisers of facial creams use either celebrities or actors dressed as scientists
to try to sell the product. Explain their reasoning. (2 marks)
..........................................
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Topic 7
End of unit test
Contents
146
TOPIC 7. END OF UNIT TEST
End of Unit 3 test
Q1: Complete the sentences by matching the parts on the left with the parts on the
right. (12 marks)
The central nervous system comprises the brain and
sensory information.
The sympathetic and parasympathetic nervous systems act
information.
The limbic system influences the pituitary through the
secretion of
the spinal cord.
Perception is the process by which the brain analyses
incoming
severe injury.
Information is lost from Short-Term Memory by
antagonistically.
Glial cells support and maintain neurons by removing
debris by
attachment.
Increased endorphin production is associated with
persuasion.
Recreational drugs may inhibit the enzymatic degradation
of
hormones.
A trait that becomes evident between six and nine months
after birth is
experience.
Language uses symbols to represent
phagocytosis.
Learning is a change in behaviour brought about by
neurotransmitters.
Internalisation is the changing of beliefs as a result of
displacement or
decay.
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TOPIC 7. END OF UNIT TEST
147
..........................................
In an experiment into the serial position effect, pupils in a class were shown how to
answer by watching a teacher do a similar experiment. They were then shown twelve
pictures and asked to recall them.
The table below records their success at recalling each picture.
Pupil
1
2
3
4
5
1st
2nd
3rd
4th
√
√
√
√
√
√
√
√
√
√
√
√
80
80
Recall
100
(%)
6th
7th
8th
√
9th
√
√
√
√
5th
√
√
√
?
√
√
20
√
√
√
40
10th 11th 12th
40
Position of picture in list shown to pupils:
40
√
60
√
√
√
√
√
√
√
√
√
√
√
√
80
100
80
= picture recalled
Q2: What is the percentage recall of the 5th picture? (1 mark)
..........................................
Q3: Express the percentage recall of the 3rd and 9th pictures as a simple wholenumber ratio. (1 mark)
..........................................
Q4: Describe the trends shown in the data. (2 marks)
..........................................
Q5: Suggest two ways in which the reliability of this experiment might be improved. (1
mark)
..........................................
Q6: Suggest two variables that would have to be kept constant in this experiment. (2
marks)
..........................................
Q7: Predict how the results table would look if twenty pictures had been used instead
of twelve. (1 mark)
..........................................
Q8: With reference to the brain, state two functions regulated by the medulla. (2
marks)
..........................................
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TOPIC 7. END OF UNIT TEST
Q9: What is the part of the brain that is responsible for muscular co-ordination? (1
mark)
..........................................
Q10: State one secretory function of the hypothalamus. (1 mark)
..........................................
Q11: State one regulatory function of the hypothalamus. (1 mark)
..........................................
Q12: Name one state that the limbic system influences. (1 mark)
..........................................
Q13: Name the neurotransmitter involved in the reward pathway. (1 mark)
..........................................
Perception is the process by which the brain analyses and makes sense of incoming
sensory information.
Q14: Into what do we organise our perceptions to segregate them? (1 mark)
..........................................
Q15: State two visual clues used in the perception of distance. (2 marks)
..........................................
Q16: What feature is most important in the recognition of objects? (1 mark)
..........................................
Q17: What does language use to represent information? (1 mark)
..........................................
Q18: What term is used to describe the process by which a child who has been
scratched by a cat comes to fear all cats? (1 mark)
..........................................
Q19: What causes some-one to change their beliefs by internalisation? (1 mark)
..........................................
..........................................
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GLOSSARY
Glossary
Addiction
continued indulgence in a behaviour despite the negative consequences - may be
psychological (a habit) or physiological (a dependence)
Antagonistic
muscles which work against each other at a joint to produce controlled movement,
e.g. biceps and triceps at the elbow
Autonomic nervous system
(ANS) responsible for involuntary homeostatic control of many body functions
Axon
the long, slender projection of a neuron, that typically conducts impulses in one
direction, away from the neuron's cell body and dendrites to the axon terminals
Behaviour
the response of an organism to internal and external stimuli
Binocular disparity
our two eyes have a slightly different view of the same scene because their pupils
are about 65mm apart
Cell body
part of the neuron which contains the nucleus with its DNA and which controls the
activity of the cell
Central core
the medulla and the cerebellum
Central nervous system
(CNS) the brain, spinal cord, retina and optic nerve
Cerebellum
part of the brain which controls balance and muscular coordination
Cerebral cortex
the thin outer layer of the cerebrum, comprising three parts: the sensory, motor,
and association areas
Chunking
the grouping of separate items of information so they pass into memory as a single
unit
Dendrite
part of the neuron which carries impulses towards the cell body
Desensitisation
the effect of the drug reduces with repeated exposure because there is a decrease
in the number and sensitivity of receptors - the drugs involved are agonists
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150
GLOSSARY
Discrimination
identifying key features of an object to distinguish it from similar objects
Dopamine
neurotransmitter involved in the reward pathway of the brain, which is also
important in a wide range of other brain functions including sleep, mode, attention,
working memory, and learning
Double circulation
a blood circulation which passes the blood through the heart twice for every
complete pass around the body
Effector
any organ capable of responding to a stimulus from a motor neuron, e.g. muscles,
glands
Elaboration
linking new information with emotions, images and other memories
Elaborative encoding
transfer of information from STM to LTM by elaboration
Encoding
process by which information is converted into a form which can be passed from
STM to LTM
Endocannabinoid
lipid signalling molecules which act like neurotransmitters in some ways, but are
very different in others
Endorphins
opioid peptides produced by the pituitary gland and hypothalamus which act as
neurotransmitters to reduce pain and increase feelings of well-being
Figure
object differentiated from its surroundings (ground)
GABA
gamma-amino-butyric acid is an inhibitory neurotransmitter found at most fast
inhibitory synapses throughout the brain
Generalisation
the process by which a response learned in reaction to one stimulus is evoked by
a different, but similar, stimulus
Glial cells
cells that support and maintain neurons
Grey matter
comprises the cell bodies of neurons and unmyelinated neurons (which lack a fatty
myelin sheath)
© H ERIOT-WATT U NIVERSITY
GLOSSARY
Ground
background sensory information against which objects (figures) are discerned
Hippocampus
part of the limbic system, located in the lower central region of the cerebrum,
which is important in moving information from short- to long-term memory and
spatial navigation
Hypothalamus
a small portion of the brain lying in the centre at the base of the cerebrum; part
of the limbic system which links the nervous system to the endocrine system
through the pituitary gland; also controls body temperature, hunger, thirst, sleep
and circadian cycles through the autonomic nervous system
Identification
changing of one's beliefs to those of an admired influencing source
Imitation
behaviour whereby an individual observes and replicates another's
Impulse
the temporary reversal of the electrical potential difference across the plasma
membrane of the cell of a neuron which passes along the axon of a neuron
Innate
inborn
Internalisation
changing of one's beliefs as a result of persuasion
Interneuron
a neuron which connects with other neurons (including sensory, motor or other
interneurons) in the CNS
Limbic system
located at the base of the cerebrum, this is a system consisting of many parts
of the brain, including the hypothalamus, which is concerned with the formation
of memories, and influences emotional and motivational states; it also regulates
blood pressure, body temperature and water balance
Medulla
part of the brain which controls heart rate, breathing rate and blood pressure, as
well as several simple reflexes
Memory span
the number of items that can be stored in Short-Term Memory
Metabolic activity
all of the chemical reactions going on within cells
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151
152
GLOSSARY
Mood
a psychological state which is less immediately affected by events than emotion,
and less permanent than personality or temperament
Motor neuron
a neuron which connects effectors such as the muscles or glands to the central
nervous system
Motor skills
sequences of movements that are necessary to perform a particular task
Myelin
a substance made largely of lipoprotein which is wrapped around the axon of
sensory-motor neurons by a type of glial cell called a Schwann cell
Nerve
an enclosed bundle of axons in the peripheral nervous system (in the CNS these
are known as tracts)
Neuroglia
glial cells
Neuromuscular junction
the connection between the axon terminal of a motor neuron and a muscle fibre
Neuron
a cell that transmits and processes information by means of electrical and chemical
signals; such cells are often referred to as nerve cells, which is strictly incorrect
because nerves contain other types of cells as well as neurons, e.g. Schwann
cells
Neurotransmitters
a range of chemicals which convey messages between neurons, or neurons and
effectors
Opioid
substances which attach to the opioid receptors in the central and peripheral
nervous systems - endorphins are the chemicals made in the body which do this
Organisation
grouping new information with other similar items in memory
Pacemaker
also known as the sinoatrial node (SAN), a group of modified heart muscle cells
which generate the electrical impulses that regulate the contractions of the heart;
located in the upper part of the right atrium, the SAN naturally generates impulses
between 60 - 100 times a minute
Parasympathetic nervous system
causes decreases in heart and breathing rates, and increases in peristalsis and
intestinal secretions
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GLOSSARY
Perception
the process by which the brain analyses and interprets incoming sensory
information
Perceptual constancy
despite changing conditions of size, shape and colour, familiar objects are
perceived in the same way
Peripheral nervous system
(PNS) all of the sensory and motor neurons outside of the central nervous system
which conduct impulses to and from it
Phagocytosis
absorption of materials into the cell by engulfing
Pituitary gland
an endocrine gland about the size of a pea, which, although not part of the brain,
is attached to the hypothalamus at the base of the brain; secretes nine hormones
which regulate homeostasis
Postsynaptic
a neuron which carries receptors to bind to neurotransmitters released by the
presynaptic neuron in response to the arrival of a stimulus
Presynaptic
a neuron at which an impulse arrives first at a synapse, and which releases
neurotransmitters to signal to the postsynaptic neuron
Receptor
a specialised neuron which responds to stimulation by a particular stimulus
Recognition
identifying a perceived object as having been encountered before
Reflex
behaviour involving a reflex arc of sensory, inter and motor neurons, which is rapid,
involuntary and often protective in nature
Reflexes
rapid, automatic responses to stimuli, usually involving a sensory, inter- and motor
neuron reflex arc - many are protective (e.g. knee-jerk to regain balance), but
others are part of routine bodily functions (e.g. swallowing)
Reinforcement
action which makes a behaviour more likely to be repeated
Relative height
the position of an object relative to the top and the bottom of an image
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GLOSSARY
Relative size
if two objects are of the same shape, the larger is perceived as closer
Retina
light-sensitive tissue lining of the inner surface of the eye which is considered part
of the CNS, and is actually brain tissue
Retrieval
recall from LTM to the Working Memory of STM
Reward pathway
interconnected areas of the cerebral cortex and mid-brain which regulate and
control behaviour by inducing pleasurable effects and, when activated, reinforce
behaviours
Rods
cells in the retina which react to light of all colours, but are much more responsive
to light than the cones which can distinguish colour - by connecting to interneurons
in a convergent neural pathways, they further increase their sensitivity
Segregation
sorting sensory information by separating it into coherent objects and their
surroundings
Sensitisation
the effect of a drug increases the more it is taken as a result of an increase in the
number and sensitivity of neurons - the drugs involved are antagonists
Sensory neuron
a neuron which connects sense receptors to the central nervous system
Serotonin
a neurotransmitter found mainly in the gastrointestinal tract (gut), platelets and
central nervous system (CNS) - in the CNS it regulates mood, appetite and sleep,
as well as being involved in memory and learning
Shallow encoding
transfer of information from STM to LTM by rehearsal
Shaping
differential reinforcement of successive approximations to a desired behaviour
Somatic nervous system
controls the voluntary movement of skeletal muscles
Stimulus
(plural: stimuli) a change in the environment, internal or external, detected by an
organism
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GLOSSARY
Superimposition
when objects overlap, the one which is partially obscured is perceived to be further
away
Sympathetic nervous system
causes increases in heart and breathing rates, and decreases in peristalsis and
intestinal secretions
Synapse
the junction between the axon terminal of one neuron and the dendrite of the next
in a neural pathway
Synaptic cleft
the gap between the axon terminal of a presynaptic neuron and the dendrite of a
postsynaptic neuron at a synapse
Tolerance
increasing doses of a drug are required to achieve the same effect. Results
from the reduction in the number and sensitivity of receptors caused by repeated
exposure to agonist drugs
Vesicles
small lipoprotein-lined, vacuole-like structures, in the case of synaptic vesicles
about 40nm in diameter
Visual cortex
each cerebral hemisphere has a visual cortex that is located at the back of the
brain, the one on the left processing visual information from the right eye and vice
versa
Visual cue
the aspect of an image which is used to estimate relative positions of objects or
their distance from us
Wake-sleep cycle
the daily rhythm of waking and sleeping, determined by the internal body clock
and fine-tuned to environmental cues
White matter
largely composed of myelinated axons
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ANSWERS: TOPIC 1
Answers to questions and activities
1 The structure of the nervous system
Introduction to the structure of the nervous system: Questions (page 3)
Q1:
a) the central nervous system
Q2:
b) muscles and glands
Q3:
a) the central nervous system
Q4:
b) motor neurons
Q5:
a) interneurons
Divisions of the nervous system: Question (page 5)
Q6:
Autonomic nervous system: Question (page 10)
Q7:
Sympathetic
Parasympathetic
Heart rate
Increased
Decreased
Stroke volume
Increased
Decreased
Breathing rate
Increased
Decreased
Depth of breathing
Increased
Decreased
Contractions of smooth
muscle of gut wall
Decreased
Increased
Intestinal secretions
Decreased
Increased
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Parts of the brain: Question (page 11)
Q8:
The central core: Question (page 12)
Q9:
Medulla
Cerebellum
arousal
balance
breathing
movement
heart rate
muscular coordination
sleep
posture
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ANSWERS: TOPIC 1
Limbic system and cerebral cortex: Question (page 20)
Q10:
Process
Area
Controls voluntary movement
motor area
Processes information for the formation
of memories
limbic system
Transfers information between
hemispheres
corpus callosum
Influences the secretions of the pituitary
hypothalamus
Recalls memories
cerebral cortex
Deals with language and imagination
association area
Receives impulses from the skin
somatosensory area
Centre of conscious thought
cerebral cortex
Controls the left side of the body
right cerebral hemisphere
Acts as an integrated whole
brain
Extended response question: Nervous system (page 23)
Suggested marking scheme
Each line represents a point worth one mark. The concept may be expressed in other
words. Words which are bracketed are not essential. Alternative answers are separated
by a solidus (/); if both such answers are given, only a single mark is allocated. In
checking the answer, the number of the point being allocated a mark should be written
on the answer paper. A maximum of ten marks can be gained.
A) Divisions of the nervous system(maximum of 5 marks):
1. The nervous system is divided into the central nervous system and the
peripheral nervous system.
2. The central nervous system consists of the brain and spinal cord.
3. The peripheral nervous system comprises all the sensory and motor neurons
which connect it to the rest of the body.
4. The peripheral nervous system is sub-divided into the somatic and the
autonomic nervous systems.
5. The somatic nervous system controls the voluntary activity of the skeletal
muscles (and thus all movement) via its sensory and motor neurons.
6. The autonomic nervous system is further divided into the sympathetic and
the parasympathetic nervous systems, which act antagonistically.
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B) Homeostatic control (maximum of 5 marks):
i
The autonomic nervous system plays an important part in many involuntary
homeostatic processes. . .
ii
. . .by conducting impulses through its sensory and motor neurons to the
smooth muscle of artery walls, the cardiac muscle of the heart, and to glands.
iii The sympathetic nervous system prepares the body for action, 'fight or
flight'. . .
iv . . .by speeding up heart and breathing rates, and slowing down peristalsis
and intestinal secretions.
v
The parasympathetic nervous system calms the body down, 'rest and
digest'. . .
vi . . .by slowing down the heart and breathing rates, and increasing peristalsis
and intestinal secretions.
End of Topic 1 test (page 24)
Q11:
Types of neuron:
sensory, motor,
interneuron.
Connect sense receptors to CNS:
sensory neurons.
Connect CNS to muscles and glands:
motor neurons.
Connect to other neurons of all types:
interneurons.
Analysis of information:
central nervous system.
Muscular contractions and glandular secretions:
motor responses.
Divisions of the nervous system:
central and peripheral.
Central nervous system comprises:
brain and spinal cord.
Divisions of the peripheral nervous system:
somatic and autonomic.
Sympathetic and parasympathetic:
autonomic nervous
system.
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Q12:
Controls the movement of skeletal muscles:
somatic nervous system.
Skeletal muscle control by sensory and motor
neurons is:
voluntary.
Responsible for involuntary homeostatic control:
autonomic nervous
system.
Involuntary homeostatic control involves:
sensory and motor
neurons.
Motor neurons of the autonomic nervous system
connect to:
smooth and cardiac
muscle.
Action of the sympathetic and parasympathetic
nervous system:
antagonistic.
Increases heart rate, decreases intestinal secretions:
sympathetic nervous
system.
Decreases breathing rate, increases peristalsis:
parasympathetic nervous
system.
Q13: Cerebrum
Q14: Cerebellum
Q15: Central nervous system
Q16: To pass information between the cerebral hemispheres.
Q17:
Q18: Any two from:
• arousal;
• breathing;
• heart rate;
• sleep.
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ANSWERS: TOPIC 1
Q19: Cerebellum
Q20: Central
Q21: Peripheral
Q22: Brain
Q23: Somatic
Q24: Sympathetic
Q25: Sensory and motor neurons.
Q26: Any two from:
• cardiac muscle;
• glands;
• smooth muscle.
Q27: Decrease
Q28: Increase
Q29: Limbic system
Q30: Hormones
Q31: Any two from:
• blood pressure;
• body temperature;
• water balance
Q32: Cerebral cortex
Q33: Sensory and motor
Q34: Any three from:
• imagination;
• intelligence;
• language;
• personality;
• thought.
(any one or two correct for 1 mark, any three correct for 2 marks)
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ANSWERS: TOPIC 2
2 Perception and memory
Segregation of objects: Questions (page 33)
Q1: To prevent the shape of the object being recognised against its background as its
edges are no longer clear.
Q2:
They enable the organisation of stimuli into coherent patterns.
Perception of distance: Question (page 37)
Q3:
• Relative size - the human figures, parasols and the paving setts are smaller towards
the front of the building.
• Superimposition - the sign in the foreground partly conceals the people behind it;
the parasols in the mid-ground partly conceal those closer to the building.
• Relative height in the field - the sign at the foot of the photo appears much closer
than the tables higher in the image.
Location of Sensory Memory: Question (page 42)
Q4:
Serial position effect 2 (page 44)
Q5: The first few items are recalled from Long-Term Memory, possibly using
mnemonics. The middle few items are often not recalled at all. The last few items
are still in Short-Term Memory.
Q6:
Seven items are usually held in the Short-Term Memory.
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Q7: If it is a particularly unusual item or a favourite item of the subject.
Short-Term Memory: Questions (page 45)
Q8:
Memory span of STM is:
7 (5-9) items.
Items remain in STM for:
15-30 seconds.
Items are maintained in STM by:
rehearsal.
Items are lost from STM by:
displacement and decay.
STM memory span can be increased by:
chunking.
Working Memory is an extension of:
STM.
Working Memory is used to perform:
cognitive tasks.
Q9:
i
The early numbers have been rehearsed by repetition.
ii
The later numbers are still in STM.
iii The middle numbers have been displaced from STM.
Long-Term Memory: Question (page 47)
Q10:
Process by which information is converted to a form
which can stored in memory:
encoding.
Transfer from STM to LTM by repetition:
rehearsal.
Transfer from STM to LTM by grouping with similar
items:
organisation.
Transfer from STM to LTM by linking with existing
memories:
elaboration.
Encoding produced by repetition:
shallow.
Encoding produced by linking with emotions:
elaborative.
Recall from LTM to STM:
retrieval.
Clues which aid recall:
contextual.
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ANSWERS: TOPIC 2
Location of memory in the brain: Questions (page 49)
Q11:
Type of memory
Information stored
Episodic
Events and experiences
Semantic
Facts and concepts
Procedural
Motor and cognitive skills
Emotional
Emotional responses
Spatial
Location of physical objects in space
Q12:
Events and experiences; Facts
and concepts:
area of cerebral cortex where sensory
information first encoded.
Motor and cognitive skills:
located in the motor cortex.
Emotional responses:
located in the amygdala of the cortex and the
limbic system.
Location of physical objects in
space:
located in the hippocampus of the limbic
system.
Extended response question: Short-Term Memory (page 54)
Suggested marking scheme
Each line represents a point worth one mark. The concept may be expressed in other
words. Words which are bracketed are not essential. Alternative answers are separated
by a solidus (/); if both such answers are given, only a single mark is allocated. In
checking the answer, the number of the point being allocated a mark should be written
on the answer paper. A maximum of ten marks can be gained.
A) Increasing memory span (maximum of 3 marks):
1. Memory span is the number of items that can be retained in STM.
2. The normal short-term memory span is 7± 2 items.
3. Information is retained in STM for 15-30s.
4. 'Chunking' of memory helps short-term memory in particular as several items
are grouped as one.
B) Serial position effect (maximum of 5 marks):
i
A large number of items is shown briefly to the subjects so that they cannot
all be retained in short-term memory.
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165
Items recalled by the subjects are recorded.
iii Subjects usually recall items presented early and late in the series.
iv Items at the end of the series are still retained in STM (the recency effect).
v
Items from the start of the series have been transferred to long-term memory
(the primacy effect).
vi Items from the middle of the list have been displaced from STM. . .
vii . . .and have not been transferred to LTM.
C) Transfer from STM to LTM (maximum of 2 marks):
I
Rehearsal - repetition of information.
II Elaboration of meaning by linking to other memories/emotions.
III Organisation - linking to other similar memories.
End of Topic 2 test (page 54)
Q13:
In the field, distance is judged by visual cues such as relative size, superimposition,
and relative height.
Relative size refers to the apparent dimensions of similar objects, overlap of objects
is used in superimposition, and relative height refers to position in the image.
At close range, binocular disparity is also used. This uses the fact that each eye has a
different viewpoint.
We perceive familiar objects in the same way despite changing circumstances, such as
viewing angle, because of perceptual constancy.
Q14:
Conversion of information into a form that can be passed into LTM:
encoding.
Repetition of information:
rehearsal.
Grouping of items of information which are similar:
organisation.
Linking information with emotions and images:
elaboration.
Type of encoding produced by repetition:
shallow.
Forms more permanent memories than shallow encoding:
organisation
and
elaboration.
Recall from LTM to Working Memory:
retrieval.
Cues which relate to the conditions under which a memory was
formed:
contextual.
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ANSWERS: TOPIC 2
Q15:
Memory of events and experiences:
episodic.
Memory of facts and concepts:
semantic.
Memory of motor and cognitive skills:
procedural.
Memory of how we felt about past events:
emotional.
Memory of the location of objects:
spatial.
Part of the brain where all memory is located:
cerebrum.
Where memories of events and facts are stored:
sensory regions of
cortex.
Where skill-related memories are linked to long-term
changes:
motor cortex.
Our feelings about past events involve links between:
cortex and limbic
system.
Part of the limbic system:
hippocampus.
Q16: perception
Q17: figures
Q18: ground
Q19: coherent
Q20: segregation
Q21: b) shape
Q22: c) recognition
Q23: c) inference
Q24: c) inference
Q25: The process of storage, retention and retrieval of information.
Q26: Sensory
Q27: Sensory
Q28: memory span
Q29: rehearsal
Q30: displacement
Q31: decay
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Q32: chunking
Q33: Working Memory
Q34:
Average number of items held:
memory span.
Maintains items in STM:
rehearsal.
New information causes loss:
displacement.
Without repetition, items are lost:
decay.
Improves STM:
chunking.
Performs cognitive tasks involving information in STM:
working memory.
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ANSWERS: TOPIC 3
3 Neurons, neurotransmitters and neural pathways
Structure of neurons: Question (page 64)
Q1:
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Neurons: Question (page 68)
Q2:
Neurons:
type of nerve cell.
Neurons receive and transmit:
impulses.
Neurons comprise:
cell body, axon and dendrites.
DNA in the cell body codes for:
all cell proteins.
Carry impulses towards the cell
body:
dendrites.
Axon terminals and dendrites form:
synapses.
The gap between an axon terminal
and a dendrite:
synaptic cleft.
Junction between an axon and a
muscle fibre:
neuromuscular.
Glial cells: Question (page 70)
Q3:
The nervous system contains more than neurons. About 15% of the cells in the
cerebrum are glial cells which support and maintain the neurons in several ways.
Some of them monitor the conditions surrounding the neurons and maintain a constant
environment by homeostasis. Others help repair damage by removing cell debris by
phagocytosis.
Another cell of this type, called the Schwann cell, wraps lipoprotein membrane around
axons forming the myelin sheath, the effect of which is to greatly accelerate the
conduction of impulses. Starting well before birth, this process, known as myelination,
continues until adolescence. This explains why an infant's responses to stimuli are less
coordinated than an adult's.
Myelination: Question (page 71)
Q4: 0.08
Neurotransmitters: Questions (page 74)
Q5: To ensure that they do not act on cell contents and to conserve resources.
Q6: Mitochondria: supply energy for active uptake of noradrenaline after its use and
to provide energy for cellular functions.
Ribosomes: synthesise proteins essential to produce neurotransmitters.
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ANSWERS: TOPIC 3
Neural pathways: Questions (page 81)
Q7:
a) converging
Q8:
b) diverging
Q9:
c) reverberating
Q10: a) converging
Q11: b) diverging
Q12: c) reverberating
Q13: b) plasticity
Q14: a) brain damage
Extended response question: Sensory and motor neurons (page 85)
Suggested marking scheme
Each line represents a point worth one mark. The concept may be expressed in other
words. Words which are bracketed are not essential. Alternative answers are separated
by a solidus (/); if both such answers are given, only a single mark is allocated. In
checking the answer, the number of the point being allocated a mark should be written
on the answer paper. A maximum of ten marks can be gained.
1. Sensory neurons pass messages from sense organs to the central nervous
system whereas motor neurons transfer messages from the CNS to muscles and
glands.
2. Both neurons consist of cell body, axon and dendrites.
3. The cell body is found part way along the axon of a sensory neuron, whereas the
axon grows out from one side of the cell body in the motor neuron.
4. In each case, the axon is wrapped in a myelin sheath with nodes every few
millimetres.
5. At a synapse, neurotransmitters cross from the pre-synaptic neuron to the postsynaptic neuron.
6. Neurotransmitters include acetylcholine and noradrenaline.
7. The type of receptor on the post-synaptic dendrite, to which the transmitter
chemical binds, determines whether the next neuron is inhibited or excited.
8. Acetylcholine is immediately degraded by an enzyme.
9. Noradrenaline is reabsorbed by active uptake.
10. Synapses filter out single weak impulses, but can sum several weak impulses.
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End of Topic 3 test (page 86)
Q15:
Cells that make up the nervous system:
neurons.
Transmitted through the nervous system:
impulses.
Neurons that carry information into the CNS:
sensory.
Neurons that connect neurons:
interneurons.
Neurons that connect the CNS to glands:
motor neurons.
Carry impulses towards the cell body:
dendrites.
Found at the end of the axon:
axon terminals.
Increases speed of conduction of impulses:
myelin.
Cells which produce the myelin sheath:
glial.
Results from destruction of the myelin sheath:
multiple sclerosis.
Q16:
Neurotransmitters are chemicals which relay signals between neurons in the CNS
and between neurons and glands. The junction between neurons is called a
synapse and that between neurons and muscle fibres is a neuromuscular junction.
Neurotransmitters are secreted by exocytosis into synaptic cleft, and diffuse across
the gap and bind to receptors on the dendrites of the next neuron.
Signals may be excitatory or inhibitory, depending only on the receptor on the
receiving dendrite and not on the type of neurotransmitter. Neurotransmitters must be
immediately removed to prevent continuous stimulation of the post-synaptic neurons.
Neurotransmitters are either removed by enzyme action (e.g. acetylcholine) or by reuptake (e.g. noradrenalin).
Synapses can filter out weak impulses arising from insufficient secretion of
neurotransmitter.
If sufficient neurotransmitters attach to the receptors, a threshold is reached and an
impulse is triggered. By summation a series of weak stimuli can combine to reach the
firing threshold in the post-synaptic neuron.
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ANSWERS: TOPIC 3
Q17:
Several neurons pass messages on to a single neuron:
converging pathway.
An example of a converging pathway:
rods in the retina.
Increased by a converging pathway:
sensitivity to signals.
A single neuron passes messages on to several neurons:
diverging pathway.
An example of a diverging pathway:
fine motor control.
Neurons later in the pathway synapse with earlier ones:
reverberating
pathway.
An example of a reverberating pathway:
wake-sleep cycle.
New responses are created by their development:
new neural
pathways.
Result of the development of new neural pathways:
plasticity of
response.
Q18: Dendrites
Q19: Axon
Q20: Axon terminals
Q21: It is found surrounding the axon, and its function is to insulate the axon and speed
up neuron transmission.
Q22: Motor
Q23: Other neurons
Q24: Sensory
Q25: Synaptic cleft
Q26: Neuromuscular junction
Q27:
• Maintaining a constant environment around the neuron.
• Producing myelin sheath.
• Removing debris by phagocytosis.
Q28: Multiple sclerosis (or other suitable)
Normal neuron transmission is prevented leading to loss of co-ordination.
Q29: Synaptic vesicles
Q30: The arrival of a nerve impulse.
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ANSWERS: TOPIC 3
Q31: Diffusion
Q32: Receptors
Q33: It is the process by which several weak stimuli combine. . .
. . .to reach the threshold to fire/release an impulse in the post-synaptic neuron.
Q34: Converging
Q35: Rods in the retina (other answers are possible)
Q36: A single neuron passes messages on to several neurons.
Q37: Converging
Q38: Wake-sleep cycle (other answers are possible)
Q39: Plasticity of response
Q40: Any two from:
• bypass areas of brain damage;
• create new responses;
• suppress reflexes;
• suppress responses to sensory impulses.
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ANSWERS: TOPIC 4
4 Neurotransmitters, mood and behaviour
Dopamine and the reward pathway: Question (page 93)
Q1: Organisms which do not carry out key activities will not rear many offspring or
even survive.
Linking an activity to the reward pathway will increase its frequency / intensity; the
organism is more likely to carry out these beneficial activities.
Endorphins: Questions (page 95)
Q2:
They inhibit the triggering of impulses in the neurons linked to pain receptors.
Q3: Beneficial: after a serious accident, an injured person may still be able to help
others or walk to find help.
Detrimental: during a tight game, a footballer may damage a muscle but continue to
play, only to later discover the extent of her injury.
Q4: Both sexual orgasm and the close physical presence of a loved one increase
endorphin secretion.
Increased endorphin levels lead to feelings of pleasure and euphoria.
Without these feelings, it is hard to sustain a partnership.
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Neurotransmitter-related disorders and their treatment: Question (page 99)
Q5:
Disorder
Alzheimer's
disease
Parkinson's
disease
Area of brain
affected
Cerebral cortex
and mid-brain
Mid-brain
Neurotransmitters
involved
Drug Treatment
Acetylcholine
Acetylcholinesterase
inhibitor to raise
neurotransmitter
levels by slowing
degradation
Dopamine
L-DOPA as
precursor of
dopamine;
dopamine agonists;
MAO-B inhibitors to
slow dopamine
degradation
Schizophrenia
Reward pathway
Dopamine
Dopamine
antagonists to slow
uptake
Generalised
anxiety disorder
Amygdala in cortex
Serotonin
Norepinephrine
GABA receptor
agonists,
Beta-blockers
Brain-stem near
medulla
Serotonin
Norepinephrine
Dopamine
Drugs inhibiting
norepinephrine
re-uptake; MAO-B
to inhibit dopamine
degradation
Depression
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ANSWERS: TOPIC 4
Modes of action: Question (page 103)
Q6:
Drug
Mode of action
Neurotransmitter
Stimulating the release of
neurotransmitters
MDMA
serotonin
Agonists
Cannabis
GABA
Antagonists
Ethanol
glutamate
Inhibition of re-uptake of
neurotransmitters
Cocaine
serotonin,
norepinephrine and
dopamine
Inhibition of degradation of
neurotransmitters
Tobacco - monoamine
oxidase (MAO) inhibitors
monoamine oxidase
(MAO)
Drug addiction, sensitisation and tolerance: Questions (page 104)
Q7:
Changes to the number and sensitivity of receptors.
Q8:
An increase in the number and sensitivity of receptors.
Q9:
Antagonists
Q10: Addiction
Q11: A decrease in the number and sensitivity of receptors.
Q12: Agonists
Q13: Tolerance
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Extended response question: The mode of action of recreational drugs (page
106)
Suggested marking scheme
Each line represents a point worth one mark. The concept may be expressed in other
words. Words which are bracketed are not essential. Alternative answers are separated
by a solidus (/); if both such answers are given, only a single mark is allocated. In
checking the answer, the number of the point being allocated a mark should be written
on the answer paper. A maximum of ten marks can be gained.
A) Effects on the brain (maximum of 4 marks):
1. Recreational drugs mainly affect the reward circuit of the brain. . .
2. . . .by stimulating increased secretion of dopamine. . .
3. . . .which causes feelings of euphoria and relaxation. . .
4. . . .and leads quickly to addiction.
5. The changed neurochemistry leads to changes in mood / cognition /
perception / behaviour. (mention of all four examples gains this mark)
B) Modes of action (maximum of 6 marks):
i
Stimulation of release of neurotransmitter, . . .
ii
. . .e.g. MDMA stimulates release of serotonin.
iii Agonists , imitating the action of a neurotransmitter, . . .
iv . . .e.g. cannabis binds to cannabinoid receptors and suppresses GABA
secretion.
v
Antagonists bind to receptors and prevent neurotransmitter from doing so, . . .
vi . . .e.g. ethanol binds to GABA receptors and depresses impulse generation.
vii Inhibiting re-uptake of neurotransmitter, . . .
viii . . .e.g. cocaine blocks the re-uptake of serotonin / norepinephrine / dopamine.
ix Inhibiting neurotransmitter degradation, . . .
x
. . .e.g. tobacco contains two MAO inhibitors which suppress dopamine
breakdown.
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ANSWERS: TOPIC 4
End of Topic 4 test (page 107)
Q14:
The reward pathway involves neurons which secrete dopamine, which induces the
feeling of pleasure and so reinforces particular behaviours. The reward pathway is
activated by beneficial behaviour.
Endorphins stimulate neurons involved in reducing the intensity of pain. Increased
levels of endorphins are connected with appetite modulation. Increased endorphin
production is associated with the consumption of certain foods.
Many of the drugs used to treat neurotransmitter-related disorders are similar to
neurotransmitters. Agonists bind to and stimulate receptors, thus mimicking the
neurotransmitter. Antagonists bind to specific receptors, so blocking the action of
a neurotransmitter. Other drugs inhibit the enzymes which degrade neurotransmitters,
or inhibit reuptake.
Q15:
Many recreational drugs affect neurotransmission in the
reward pathway.
Changes in neurochemistry alter mood, cognition,
perception and
behaviour.
Recreational drugs may stimulate the
release of
neurotransmitters.
Recreational drugs may inhibit the
re-uptake of
neurotransmitters.
Drugs which imitate the action of neurotransmitters are
agonists.
Drugs which block the binding of neurotransmitters are
antagonists.
An increase in the number and sensitivity of receptors is
sensitisation.
Sensitisation results from exposure to
antagonist drugs.
Sensitisation leads to
addiction.
A decrease in the number and sensitivity of receptors is
desensitisation.
Desensitisation results from exposure to
agonist drugs.
Desensitisation leads to
tolerance.
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ANSWERS: TOPIC 4
Q16: Endorphins
Q17: Any three from:
• certain foods;
• prolonged and continuous exercise;
• severe injury;
• stress.
Q18: Dopamine
Q19: Pleasure / euphoria
Q20: Agonists mimic the action of the neurotransmitter.
Antagonists bind to the receptor and block the action of the neurotransmitter.
Q21: Inhibit enzymes that degrade neurotransmitters.
Inhibit neurotransmitter re-uptake.
Q22: The reward pathway/circuit.
Q23: Any three from:
• behaviour;
• cognition;
• mood;
• perception.
Q24:
• Block their binding.
• Imitate their action.
• Inhibit their degradation.
• Inhibit their re-uptake.
• stimulate their release.
Q25: An increase in the number and sensitisation of receptors.
Q26: Antagonists
Q27: Addiction
Q28: A decrease in the number and sensitisation of receptors.
Q29: Agonists
Q30: Tolerance
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ANSWERS: TOPIC 5
5 Infant attachment and the effect of communication
Imprinting: Question (page 115)
Q1:
1. Parent and infant are introduced to the experimental room.
2. Parent and infant are alone. Parent does not participate while infant explores.
3. Stranger enters, converses with parent, then approaches infant. Parent leaves
inconspicuously.
4. First separation episode: Stranger's behaviour is geared to that of infant.
5. First reunion episode: Parent greets and comforts infant, then leaves again.
6. Second separation episode: Infant is alone.
7. Continuation of second separation episode: Stranger enters and gears behaviour
to that of infant.
8. Second reunion episode: Parent enters, greets infant, and picks up infant; stranger
leaves.
Long period of dependency: Question (page 118)
Q2:
i
Reason: learning
Explanation: humans require to learn more of their behaviour than any other
animals, e.g. language
ii
Reason: socialisation
Explanation: humans have to learn how to live in complex social groups and have
to interact with others in a wide range of situations.
Parental control methods: Questions (page 119)
Q3:
Demanding
Undemanding
Responsive
Authoritative
Permissive
Unresponsive
Authoritarian
Neglectful
Q4:
i
Authoritative parenting is responsive to the child's views, involves the child in
decision making, and supports the child emotionally.
ii
Authoritative parenting sets rules and standards, and expects maturity and
cooperation.
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ANSWERS: TOPIC 5
181
Information transfer: Question (page 120)
Q5:
Non-verbal Body language
Non-verbal Gesture
Shouting out
Walking with an expanded
chest after a victory
Indicating that an archer's
bow finger will be cut off if
he gets caught
Talking
Feeling your collar when
under pressure
Pointing to your nose
when playing charades
Sobbing loudly
Showing whites of eyes
when angry
Throwing a fist in the air
Verbal
Extended response question: Human communication (page 128)
Suggested marking scheme
Each line represents a point worth one mark. The concept may be expressed in other
words. Words which are bracketed are not essential. Alternative answers are separated
by a solidus (/); if both such answers are given, only a single mark is allocated. In
checking the answer, the number of the point being allocated a mark should be written
on the answer paper. A maximum of ten marks can be gained.
A) Non-verbal communication (maximum of 4 marks):
1. Non-verbal communication involves gestures, signs, facial movements and
posture.
2. Non-verbal communication aids verbal communication.
3. Attitudes and emotions are signalled by non-verbal communication.
4. Mirroring of non-verbal communication strengthens bonds.
5. Examples of non-verbal communication include winking, folding arms and
smiling. (three listed for one mark)
6. Any two examples explained in terms of meaning conveyed.
B) Verbal communication (maximum of 6 marks):
i
Language uses symbols to represent information
ii
Language enables information to be organised into categories and
hierarchies.
iii This organisation of information accelerates learning.
iv Organisation of information aids intellectual development.
v
The ability of humans to communicate verbally has resulted in the
transmission of knowledge. (plus explanation)
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ANSWERS: TOPIC 5
vi The ability of humans to communicate verbally has resulted in the
development of culture. (plus explanation)
vii The ability of humans to communicate verbally has resulted in social
evolution. (plus explanation)
viii The ability of humans to communicate verbally has resulted in the
transmission of knowledge, development of culture and social evolution.
End of Topic 5 test (page 128)
Q6:
Early infant attachment is important for
future stable relationships.
Attachment becomes evident between
six and nine months after
birth.
Two responses to the strange situation experiment are
detachment and anger.
Infants who form secure attachments are more likely
to
investigate their
environment.
Humans have a relatively long period when they are
dependent on adults.
The long period of dependency provides opportunities
for
socialisation and learning.
Social competence can be influenced by
different methods of
control.
Authoritative control generally results in
greater social
competence.
Q7:
Non-verbal communication contributes to the formation of relationships between
individuals. It can signal attitudes and emotions, and acts as an aid to verbal
communication.
Language uses symbols to represent information and enables information to be
organised into categories and hierarchies. This organisation of information accelerates
learning and intellectual development. The ability of humans to communicate verbally
has resulted in the transmission of knowledge, development of culture, and social
evolution.
Q8:
A stranger and an observer.
Q9:
The infant's reunion behaviour with its parent/carer.
Q10: b) Insecurely attached, avoidant
Q11: a) Securely attached
Q12: 6-9 months
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ANSWERS: TOPIC 5
Q13: Socialisation and learning.
Q14: a) Authoritative
Q15: Any two from:
• child's views ignored;
• no emotional support;
• standards not set.
Q16: Attitudes and emotions.
Q17: Symbols
Q18: Categories and hierarchies.
Q19: It accelerates learning and intellectual development.
Q20: Any two from:
• development of culture;
• social evolution;
• transmission of knowledge.
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ANSWERS: TOPIC 6
6 The effect of experience and social influences
The effect of practice on motor skills: Questions (page 133)
Q1:
A change in behaviour as a result of experience.
Q2:
Motor pathway
Q3:
Repeated use
Trial and error learning: Question (page 137)
Q4:
Trial and error
involves random responses to a stimulus.
Extinct behaviour
becomes extinguished.
Reinforcement
involves making similar response to a stimulus more
likely on subsequent occasions.
Shaping
involves differential reinforcement of successive
approximations to a desired behaviour.
Generalisation and discrimination: Question (page 138)
Q5:
Generalisation
Discrimination
Not liking the people from a particular city
Only eating the sweets in the purple
wrappers
Randomly choosing any dish on the
menu
Checking the tomatoes in the
supermarket before putting them in the
bag
Enjoying travelling by train
Picking the spotted puppy from the litter
Midges spoil camping holidays in Britain
Catching the No. 54 bus at the bus
station
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ANSWERS: TOPIC 6
185
Social facilitation and deindividuation: Question (page 140)
Q6:
Performance improved by the presence of others:
social facilitation.
Performance improved in front of a crowd:
audience effect.
Performance improved by having competition:
co-actor effect.
Loss of identity in a crowd:
deindividuation.
Extended response question: Group behaviour and social influence (page 143)
Suggested marking scheme
Each line represents a point worth one mark. The concept may be expressed in other
words. Words which are bracketed are not essential. Alternative answers are separated
by a solidus (/); if both such answers are given, only a single mark is allocated. In
checking the answer, the number of the point being allocated a mark should be written
on the answer paper. A maximum of eleven marks can be gained.
A) Social facilitation (maximum of 3 marks):
1. Performance of a task may be improved in the presence of others.
2. The presence of others in a competitive situation may enhance performance
3. Detailed example of the point above
4. The presence of an audience may improve performance.
5. Detailed example of the point above
B) Deindividuation (maximum of 4 marks):
i
Deindividuation is responsible for the loss of identity in a crowd.
ii
Detailed example of the point above
iii Deindividuation leads to diminished restraints on behaviour.
iv Deindividuation leads to behaviour which would not be shown by individuals
on their own.
v
Detailed example of the point above
C) Influences that change beliefs (maximum of 4 marks):
I
Internalisation is the changing of one's beliefs as a result of persuasion.
II Detailed example of the point above
III Identification is the changing of one's beliefs to those of an admired
influencing source.
IV Detailed example of the point above
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ANSWERS: TOPIC 6
End of Topic 6 test (page 143)
Q7:
A change in behaviour brought about by experience:
learning.
An important part of learning:
observing.
Improved by repeated practice:
motor skills.
Established by practice of a motor skill:
motor pathway.
Copying behaviour:
imitation.
Makes behaviour patterns likely to be repeated:
positive outcomes.
Rewarding desired behaviour:
reinforcement.
Fate of behaviour that is not rewarded:
becomes extinct.
Rewarding behaviour as it gets closer to what is wanted:
shaping.
Q8:
Generalisation is the process by which a response learned to one stimulus is evoked
by a different but similar stimulus, whereas discrimination is the process by which
people learn to make different responses to similar stimuli.
The presence of others in a competitive situation may enhance performance, as can
the presence of an audience may improve performance. These are examples of
different types of social facilitation. Deindividuation is responsible for the loss of
identity in a crowd which may lead to diminished restraints on behaviour.
Internalisation is the changing of beliefs as a result of persuasion. Identification is the
changing of one's beliefs to those of an admired influencing source.
Q9: Behaviour with positive outcomes will be repeated;
behaviour with negative outcome will become extinct.
Q10: Desired behaviour is rewarded.
Q11: Behaviour which successively more closely approximates to the desired behaviour
is rewarded.
Q12: The child becomes afraid of small and/or white dogs, but not others
Q13: The child becomes afraid of all dogs.
Q14: Social facilitation means that individuals perform better when competing with
others and when performing in front of an audience.
Q15: Celebrities: people may want to be like the celebrity and imitate them by using the
cream.
'Scientists': people may be persuaded that they should use the product by the pseudoscience presented.
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ANSWERS: TOPIC 7
187
7 End of unit test
End of Unit 3 test (page 146)
Q1:
The central nervous system comprises the brain and
the spinal cord.
The sympathetic and parasympathetic nervous systems act
antagonistically.
The limbic system influences the pituitary through the
secretion of
hormones.
Perception is the process by which the brain analyses
incoming
sensory information.
Information is lost from Short-Term Memory by
displacement or
decay.
Glial cells support and maintain neurons by removing
debris by
phagocytosis.
Increased endorphin production is associated with
severe injury.
Recreational drugs may inhibit the enzymatic degradation
of
neurotransmitters.
A trait that becomes evident between six and nine months
after birth is
attachment.
Language uses symbols to represent
information.
Learning is a change in behaviour brought about by
experience.
Internalisation is the changing of beliefs as a result of
persuasion.
Q2: 20 %
Q3: 4:3
Q4: Percentage recall decreases from the 1st to the 5th pictures. . .
. . .then increases back up to 11th picture.
Q5:
• Increase the number of children used.
• Repeat the experiment several times.
Q6: Any two from:
• age of pupils;
• gender of pupils;
• pictures used;
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ANSWERS: TOPIC 7
• time allowed to look at the pictures;
• time delay before asking to recall the pictures after last one viewed;
• time of day when test is taken.
Q7: The first and last five pictures would be the same, the middle ten would be very
low.
Q8:
Any two from:
• arousal;
• breathing;
• heart rate;
• sleep.
Q9:
Cerebellum
Q10: Either of:
• influences the pituitary;
• secretes ADH.
Q11: Any one from:
• body temperature;
• controls contraction of smooth muscle;
• water balance.
Q12: Either of:
• emotional;
• motivational.
Q13: Dopamine
Q14: Figure and ground.
Q15: Any two from:
• relative height in field;
• relative size;
• superimposition.
Q16: Shape
Q17: Symbols
Q18: Generalisation
Q19: Persuasion
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