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2.3 Control and Communication
Learning Intentions
• Describe and identify the structures of the brain as the
cerebrum, the cerebellum and the medulla and explain
their main functions.
• State that CNS is made up of the brain and the spinal
cord.
• Describe the function of the CNS as processing sensory
information and bringing about appropriate responses.
• Explain that reflexes are rapid responses to
environmental changes and are protective in nature.
• Describe the three types of neuron involved in a reflex
arc.
• Explain the role of sensory, relay and motor neurons in
reflexes.
• State that electrical impulses move along neurons.
• State that the gaps between neurons are called synapses
and that chemicals transfer messages between neurons.
Need for Co-ordination
All the body’s organs and systems need to
be able to work together to allow the
many functions that are essential to life.
The body needs to be co-ordinated
http://www.twigonglow.com/films/the-senses-969/
Need for co-ordination
Physical activity (exercise) is one of the body’s essential
functions.
Example
When a tennis player is about to hit
the ball –
• information is picked up about where
the ball is using the sense organs (in
this case the eyes).
• This information is sent to the brain.
• The brain sends out messages to the
correct muscles to move the body in the
correct way .
There are hundreds of muscles in the body, so this can be a
very complex process.
The Nervous System
The nervous system is
composed of the brain,
the spinal cord and
nerves.
brain
spinal cord
nerves
The Nervous System
The spinal cord is
protected by the
spine.
The Nervous System
The brain sorts out information.
The spinal cord sends information
to and from the brain.
The brain and spinal cord make up
the central nervous system
(CNS).
Nerves carry information from
the senses to the CNS.
Nerves carry information from
the CNS to the muscles .
These make up the
peripheral nervous system [PNS]
The Nervous System
Information from the
sensory nerves is sorted
out by the CNS.
Information from the CNS
is then carries by the
motor nerves to the
appropriate muscles which
then contract.
The Brain
Cerebrum
Cerebellum
Medulla
Spinal Cord
The Brain
Cerebrum
Largest part of the brain. Divided into 2
halves (hemispheres – left and right). Each
region is concerned with particular functions
e.g. sensory area, motor area (movement),
hearing, sight etc.
The cerebrum is highly developed in humans.
Cerebellum
Controls balance and coordination.
Medulla
Controls the rate of breathing and heartbeat.
The Brain
motor area
transmits nerve
impulses to muscles
sensory area
receives nerve
impulses from
the senses
sight
hearing
Reflex actions
A reflex action is a rapid, automatic response
to a stimulus.
e.g. Imagine you accidentally touched a bunsen burner
which was still hot from the previous class.
How would you respond ???
The stimulus is the heat from the bunsen (pain).
The response is that you pull your hand away very
quickly. You don’t even have to think about it!!!
Reflex actions
Reflex actions happen so quickly that
there is often no time for the nerve
impulses to reach the brain. Often the
impulse only goes to the spinal cord and
the brain becomes aware of the action
only after it has happened.
See shared area for Diving reflex film
http://www.twigonglow.com/films/glossary/reflex-arc-777/
Reflex actions
Some examples are…
• pulling a limb away (hand, arm, leg etc)
• knee jerk reflex
• eye blink reflex
So reflexes protect the body from
damage.
http://www.twigonglow.com/films/factpack-reflex-arcs-1080/
The reflex arc
white matter
contains nerve
fibres
CNS
relay
neurone
sensory
neurone
Skin receptor senses pain
= signal sent STIMULUS
grey matter
contains cell
bodies
motor
neurone
muscles contract =
movement RESPONSE
Which type of nerve does what job?
Sensory nerve cells send a message
to the spinal cord. A relay nerve
connects the sensory nerve to the
motor nerve in the spinal cord. A
signal to make a muscle contract is
sent down a motor nerve.
Synapses
Gaps between
nerves are called
synapses
Electrical
impulses
cannot pass
Neurotransmitters
released from 1st
nerve
Chemicals diffuse
across synapse
Chemicals bind to
receptors of next nerve
This triggers electrical
impulse
Discovery of Neurotransmitters
Vagus nerve
slows down
heart rate
Fluid
passes
from
heart 1
container
to heart 2
container
Vagus nerve stimulated in
heart 1
Heart 2 slows down
Learning Intentions
• State the function of an endocrine gland.
• State that hormones are chemical messengers.
• State that target cells have receptors for that
hormone on their surface
• Explain that only cells that have the receptor for
the hormone are affected by the hormone.
• State that changes in blood glucose levels are
detected by the pancreas.
• Explain that when blood glucose levels increase, the
pancreas produces more insulin which in turn
activates an enzyme within its target cells (liver)
that converts glucose into glycogen.
Introduction to Hormones
http://www.twigonglow.com/films/glossary/hormones-263/
Endocrine System
Endocrine System is
made up of many glands.
These glands produce
hormones - chemical
messengers
Hormones travel in blood.
They are slow-acting.
Target tissue contains
receptors for hormone
Hormones are specific.
http://www.twigonglow.com/films/introduction-to-
Endocrine Glands
Glands and
and Secretions
Secretions
Endocrine
Endocrine
Gland
Hormone
Target
Effect
Pituitary
Pituitary
Long bones
Thyroid gland
Increase in length
Stimulates thyroxine production
Pituitary
Growth hormone
Thyroid-stimulating
hormone
Anti-diuretic hormone
Kidney tubules
Increases water reabsorption
Thyroid
Thyroxine
Bones
Body cells
Controls rate of growth and development
Controls cell metabolism
Islets of Langerhans
Insulin
liver
Controls conversion of glucose to glycogen
Adrenal
Adrenaline
brain
Increases heart and breathing rate
Sends blood to muscles
Causes conversion of glycogen to glucose
Ovary
Oestrogen
Uterus
Repairs uterus lining after menstruation
Stimulates hormone to for ovulation
Pituitary
Testis
Testosterone
Testis
Controls growth of sex organs and sexual
development
Control of blood sugar levels
• http://www.abpischools.org.uk/page/modules/hormones/horm6.cf
m
• The sugar glucose is an important source of energy for the body.
• Food is metabolised to release glucose, which is converted to CO2
and water during respiration and used to make ATP.
• If there is too much glucose in the blood then it is converted to
glycogen and stored in the liver until it is needed (it may also be
stored as fat).
• If the glucose levels are low then glycogen is converted back to
glucose, which can then be used by the body.
• The receptor cells that monitor the changes in blood sugar
levels are found in the islets of Langerhans.
• These are specialised cells in the pancreas that secrete two
different hormones in response to changes in concentration
of glucose in the blood:
– Insulin
– Glucagon
Insulin
Insulin is secreted when the blood glucose level is
high.
This hormone catalyses the conversion of glucose to
glycogen in the liver.
As a result the blood glucose level falls.
Glucagon
Glucagon is secreted when the blood glucose level is
low.
This hormone catalyses the conversion of glycogen
to glucose in the liver.
As a result the blood glucose level rises.
See shared area for film on Insulin
BOO!
• Your heart starts beating really fast, you are very
alert and you suddenly have loads of energy.
• This is because of adrenaline, a hormone that the
adrenal glands secrete to prepare the body for an
emergency (e.g. an attack).
• Adrenaline increases the body's rate of metabolism
and influences the concentration of sugar in the
blood.
The secretion of adrenaline causes the conversion of
glycogen to glucose to provide the body with enough
energy to protect itself.
When the emergency is over, the adrenaline levels
fall and the regulation of blood sugar levels is under
homeostatic control again.
Diabetes Mellitus
Some people are unable to make
enough (or any) insulin to regulate
their blood sugar levels.
This is a common disorder that is
known as diabetes mellitus (or
diabetes).
Symptoms of diabetes
• People who suffer from diabetes have high levels of glucose
in their blood as they are unable to convert it to glycogen or
fat due to a lack of insulin.
• This excess sugar is excreted in the urine; other symptoms
include rapid weight loss, dehydration and frequent urination.
• Diabetes is very dangerous and can result in a sufferer falling
into a coma and dying if it is left untreated.
• Fortunately, diabetes can be treated effectively with daily
insulin injections and a careful diet.