Download File - thebiotutor.com

5.4.2
thebiotutor.com
A2 Biology OCR
Unit F215: Control, genomes and
environment
Module 4.2 Animal responses
Notes & Questions
Andy Todd
1
5.4.2
Discuss why animals need to respond to their environment.
 Animals need to be able to coordinate a vast set of responses if they are to stay
alive
 These range from voluntary muscle actions to enable fight or flight to the fine
control of balance, posture and temperature regulation
Outline the organisation of the nervous system in terms of central and peripheral
systems in humans.
&
Outline the organisation and roles of the autonomic nervous system.


The nervous system allows humans to be receptive to their internal and external
environment, make sense of the stimuli and respond to these stumli in a way that
improves their chances of survival
The nervous system comprises of a central and peripheral system that must work
together to bring about these response to the stimuli
The Nervous System
Peripheral Nervous System PNS
Central Nervous System CNS
Made up of Billions of neurones
Grey matter – unmyelinated
White matter - myelinated
Motor Neurones
Sensory Neurones
CNS Effectors
(muscles & glands)
Receptor CNS
myelinated
Autonomic System
Somatic System
CNS Smooth muscle
Cardiac muscle
Glands
Unconscious control
Non-myelinated
2 plus neurones involved
Ganglion present
Parasympathetic pathway
Relaxation
Pre-ganglionic neurone vary
Ganglion close to target tissue
Acetylcholine
Decrease heart rate
Pupil constricts
Andy Todd
CNS Skeletal muscle
Conscious control
Myelinated
1 neurone involved
Sympathetic pathway
Stress
Short pre-ganglionic neurone
Ganglion close to Spinal cord
Nor-adrenaline
Increase heart rate
Pupil Dilates
2
5.4.2
Describe, with the aid of diagrams, the gross structure of the human brain, and
outline the functions of the cerebrum, cerebellum, medulla oblongata and
hypothalamus.
Structures
 Cerebrum
o Largest part of the brain
o Divide into two hemispheres

Cerebral Cortex
o Outer surface of the cerebrum
o Thin layer of nerve cells
o More highly developed in humans than any other organism

Cerebellum
o Over half the neurones in the brain

Corpus Callosum
o Holds the two cerebral hemispheres

Medulla Oblongata
o Found in the inner brain near the top of the spinal cord

Hypothalamus
o Found in the inner brain
Functions
 Cerebrum
o Associated with being Human
o Higher brain function
 Conscious thought
 Emotional responses
 Overriding of reflexes
 Reasoning and Judgement

Cerebral Cortex
o Divided into regions
o Sensory areas
 Receive impulses directly from sensory receptors
o Association areas
 Compares inputs from previous experiences in order to interpret what
the input means and judge an appropriate response
o Motor areas
 Sends impulses to effectors (muscles and glands)
Andy Todd
3
5.4.2

Cerebellum
o Motor processing
 Fine control of muscular movements
 Body posture
 Balance
 Dexterity
 Non-conscious operations E.g walking or driving a car etc
o Sensory processing
 The retina neurones
 Balance organs in the inner ear
 Receptors from joints

Medulla Oblongata
o Controls breathing rate (respiratory centre)
o Controls smooth muscle
o Controls Heart rate (cardiac centre)

Hypothalamus
o Controls the autonomic nervous system
o Controls the endocrine glands
o Homeostatic mechanisms
corpus callosum
cerebrum
cerebral
cortex
Front
pineal body
thalamus
hypothalamus
pituitary body
medulla oblongata
Andy Todd
corpora
quadrigemina
cerebellum
4
5.4.2
ACerebrum
Pituitary
gland
B
Cerebellum
C
DMedulla Oblongata
Andy Todd
5
5.4.2
Describe the role of the brain and nervous system in the coordination of muscular
movement.
Functions of the Cerebellum



Maintaining muscle tone and posture
Coordination of voluntary motor activity
Maintenance of balance
Cerebellum and Muscle Tone
The cerebellum has neural connections with other parts of the brain and the peripheral parts of
the body. So at any given moment it continuously receives sensory information from the bones,
joints and muscles about their position, rate and direction of movement and forces acting on
them.
The cerebellum in turn conveys this information to the motor control centers of the cortex
(motor cortex) setting the background tone and posture so that the cortex can execute new
movements based on intent. In other words, the cerebellum tells the motor cortex in what
position a limb already is and what it is doing so the cortex can plan its next move.
Andy Todd
6
5.4.2
Cerebellum and Motor Control
The cerebellum also continuously receives information on the sequence of movements desired by
the motor control areas of the cortex. With regard to movement coordination, the cerebellum
behaves like a computer, constantly comparing the actual movement of the muscle groups with the
motions intended by the motor cortex.
In case of a difference between the two, the cerebellum immediately sends signals to the muscle
groups to correct the movement so that the desired effect can be achieved, much like computers
calculating and correcting the flight path of airplanes or space vehicles.
Andy Todd
7
5.4.2
Describe how coordinated movement requires the action of skeletal muscles about
joints, with reference to the movement of the elbow joint.

The Elbow Joint

Muscle that control the elbow joint
Andy Todd
8
5.4.2

Operation of the neuromuscular junction
Explain, with the aid of diagrams and photographs, the sliding filament model of
muscular contraction.



The skeletal muscle has contractile organelles called microfibrils
These microfibrils contract by sliding filaments over each other
Each microfibril is made up of many microfilaments of which there are two types
Andy Todd
9
5.4.2

Myosin filaments
o Myosin (or thick Myosin) filaments contain many myosin molecules
o Two globular heads
o One tail

Actin Filaments
o Consists of two actin filaments (F-actin) wrapped around each other
o Each actin filament is made of individual globular actin monmers (G-actin)
o The two actin filaments are held together by Tropomyosin – a rod shaped
protein
o The thin actin filament also includes Troponin which has 3 polypeptides
 One to bind to G-actin
 One to bind to tropomyosin
 One to bind calcium ions
Andy Todd
10
5.4.2

Arrangements of these filaments
Andy Todd
11
5.4.2
Relaxed Muscle
Contracted Muscle
A Band (Myosin Filament)
I Band (Band of no over lap - Actin
Only)
H Band (Band of no over lap Myosin Only)
Same length
Same Length
Longer
Shorter
Longer
Shorter
Sarcomere (from Z-line to Z-line)
Longer
Shorter
Andy Todd
12
5.4.2
The Power stroke
 An action potential reaches the dendrite at a neuromuscular junction
 Acetylcholine is released by exocytosis into the junction and binds to
complementary receptors on the sarcolemma
 The wave of depolarisation travels along the sarcolemma nad down
transverse tubules (T-systems)
 This wave of depolarisation down the tubule excites the sarcoplasmic
reticulum.
 The sarcoplasmic reticulum releases calcium ions into the cytoplasm
 Calcium ions are involved in two processes
o Binding to troponin
o Activating ATPase
 Calcium firstly binds to troponin
 Troponin shifts out of its default position and as it does so it pulls
tropomyosin with it
 This exposes the actin myosin binding site that is blocked when the
tropomyosin is in its default position
 The myosin head can now bind to the actin filament, forming a CROSS
BRIDGE





Meanwhile other calcium ions have activated the enzyme ATPase which
catalyses the hyfrolysis of ATP  ADP + Pi releasing energy
This energy moves the myosin head at the hinge region pulling the thin actin
filament over the think myosin filament = POWER STROKE
The cross bridge is stable and so ATP needs to bind to the myosin filament to
provide energy to break the cross bridge
Now the cross bridge is broken the myosin head can bind to another actinmyosin binding site forming another cross bridge further along the actin
filament. This only occurs if there is enough calcium ions and ATP molecules
If either ATP or calcium ions are limiting then the filaments slide back to their
starting positions and the muscles relaxes
Andy Todd
13
5.4.2
Outline the role of ATP in muscular contraction, and how the supply of ATP is
maintained in muscles.
 ATP comes from three sources
o Aerobic respiration
 Requires Oxygen and respiratory substrate
 Produced rapidly in the many mitochondria
o Anaerobic respiration
 Produced quickly in the sarcoplasm
 Leads to a build up of lactic acid
 Leads to an increase of blood to the muscles
o Phosphocreatine (PCr)
 Donates phosphate to phosphorylate ADP  ATP
Phosphocreatine
ADP
Creatine Phosphotransferase
P
ATP
Phosphocreatine
Andy Todd
14
5.4.2
Compare and contrast the action of synapses and neuromuscular junctions.
Neuromuscular Junction
Synapse
Neuromuscular Junction
Synapse
Neurotransmitter is acetylcholine
Acetylcholinesterase breaks down
neurotransmitter
Various neurotransmitters
Various enzymes breaks down the
neurotranmitters
Between neurone and muscle
Between two neurones
Post junction membrane is clefted
Post synaptic membrane is smooth
Many receptors
Needs one action potentials to cause
depolarisation on post synaptic
membrane
Fewer receptors
Needs many action potentials to cause
depolarisation on post synaptic membrane
Similarities
Both release neurotranmitter by exocytosis
Calcium ions cause vesicles to migrate and fuse with prejunction membrane
Neurotransmitter crosses synapse by diffusion
Both post junction membranes have sodium channels
Andy Todd
15
5.4.2
Outline the structural and functional differences between voluntary, involuntary and
cardiac muscle.

Involuntary (Smooth) Muscle
Cardiac Muscle
Voluntary (Skeletal)
Muscle
Not Striated
Uninucleated
Contracts slowly
Fatigues slowly
Unconscious control
Single cells
Found in Walls of interstines,
arteries, bonchioles and the iris of
the eye
Striated
Multinucleated
Contracts quickly
Does not fatigue
Unconscious control
Cells branch and interlink
Striated
Multinucleated
Contracts quickly
Fatigues quickly
Conscious control
Cells in fibres
spindle shaped
Andy Todd
Found in the heart
Intercalary discs with
free ions
Found in muscles that
move the skeleton
Contain micrfibrils
16
5.4.2

Skeletal Muscles
Andy Todd
17
5.4.2

Smooth Muscles
Andy Todd
18
5.4.2

Cardiac Muscles
Andy Todd
19
5.4.2
State that responses to environmental stimuli in mammals are coordinated by
nervous and endocrine systems.
&
Explain how, in mammals, the ‘fight or flight’ response to environmental stimuli is
coordinated by the nervous and endocrine systems.
Sensory Receptors
Cerebral Cortex
Hypothalamus
Anterior Pituitary Gland
Sympathetic pathway
Glands & Smooth muscles
 Iris
 Gut Wall
 Heart rate
 Sweat
 Hairs
Releases CRF
Corticosteroid
Releasing
Factor
Adrenal Gland
Releases ACTH
AdrenoCorticoTropic
Hormone
Adrenal Cortex
Adrenal Medulla
Releases Adrenaline
Releases 30 different hormones
Blood stream
Physiological Changes
 Increase heart rate
 Increase Ventilation
 Increase Blood Glucose
 Increase Sweating
 Increase Pupil dilation
 Dilate arterioles of the liver and muscles
 Constrict arterioles of the digestive system
Andy Todd
20
5.4.2
Questions
1.
Below is a drawing of the brain that shows the origin of the cranial nerves.
A
B
C
D
(a)
State the direction from which the brain has been drawn.
.........................................................................................................................
[1]
(b)
(i)
Name the structures A, B, C and D shown on the diagram.
A .............................................................................................................
B .............................................................................................................
C .............................................................................................................
D .............................................................................................................
[4]
(ii)
State two roles of structure D.
1 .............................................................................................................
2 .............................................................................................................
[2]
Andy Todd
21
5.4.2
(c)
The hypothalamus constantly monitors and regulates the concentration of
hormones in the blood. Outline how the hypothalamus regulates the
concentration of hormones in the blood.
.........................................................................................................................
.........................................................................................................................
[2]
[Total 9 marks]
2
Calcium ions are necessary for the contraction of rabbit’s striated muscle.
Describe the role played by calcium ions in the contraction of striated muscle.
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
[Total: 3 marks]
3
The figure below shows a section through a human elbow joint.
humerus
ligament
synovial membrane
ulna
A
B
Andy Todd
22
5.4.2
(i)
Name A and B.
A ..................................................................
B ..................................................................
[2]
(ii)
Describe the roles of A and B in the movement of the elbow joint.
.........................................................................................................................
.........................................................................................................................
.........................................................................................................................
.........................................................................................................................
.........................................................................................................................
.........................................................................................................................
[3]
[Total 5 marks]
4
The cerebellum and medulla oblongata are regions of the brain. The cerebellum is
concerned with the control and coordination of movement and posture.
Suggest why the cerebellum of a chimpanzee is relatively larger than the cerebellum
of a cow.
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
[Total: 2 marks]
Andy Todd
23
5.4.2
5
The figure below shows a vertical section through the human brain.
corpus callosum
cerebrum
cerebral
cortex
Front
pineal body
thalamus
corpora
quadrigemina
hypothalamus
pituitary body
cerebellum
medulla oblongata
(i)
Name the structure shown above that links the two cerebral hemispheres.
................................................................................................................
[1]
(ii)
The table below shows the functions of some areas of the brain.
Complete the table using the labels in the figure above.
area of brain
.......................................................
.......................................................
.......................................................
.......................................................
example of function
co-ordination of posture
control of heart rate
control of temperature regulation
control of speech
[4]
[Total 5 marks]
Andy Todd
24
5.4.2
6
In this question, one mark is available for the quality of use and organisation of
scientific terms.
The following figure shows a neuromuscular junction.
motor
neurone
mitochondrion
synaptic cleft
pre-synaptic
membrane
post-synaptic
membrane
myofibril
The figure above shows that mitochondria are present on both sides of the synaptic
cleft. Explain why mitochondria are essential for the transmission of impulses across
the cleft and for muscular contraction.
transmission of impulses across the cleft .................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
Andy Todd
25
5.4.2
muscular contraction ................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
..................................................................................................................................
[8]
Quality of Written Communication [1]
[Total 9 marks]
7
(a)
The cerebellum and medulla oblongata are both parts of the hindbrain. Outline the
functions of these two parts of the brain.
cerebellum
.........................................................................................................................
.........................................................................................................................
.........................................................................................................................
.........................................................................................................................
[2]
medulla oblongata
.........................................................................................................................
.........................................................................................................................
.........................................................................................................................
.........................................................................................................................
[2]
Andy Todd
26
5.4.2
(b)
Alzheimer’s disease is characterised by several changes in the cerebrum,
including ‘tangles’ inside neurones and ‘plaques’ between neurones.
State what causes
(i)
tangles; ..................................................................................................
................................................................................................................
................................................................................................................
(ii)
plaques. .................................................................................................
................................................................................................................
................................................................................................................
[2]
Another change in the cerebrum of a person with Alzheimer’s disease is a decrease in
acetylcholine released by neurones that form memory circuits.
During a clinical trial, people with Alzheimer’s disease were treated with a drug that
inhibited the enzyme acetylcholinesterase. This improved their short-term memory.
(c)
Suggest how the drug may inhibit acetylcholinesterase.
.........................................................................................................................
.........................................................................................................................
.........................................................................................................................
.........................................................................................................................
.........................................................................................................................
.........................................................................................................................
[3]
Andy Todd
27
5.4.2
(d)
Suggest how the drug improves short-term memory.
.........................................................................................................................
.........................................................................................................................
.........................................................................................................................
.........................................................................................................................
[2]
(e)
State three precautions that should be taken when designing such clinical trials,
to ensure that any effects are due to the drugs being tested.
1 ......................................................................................................................
.........................................................................................................................
2 ......................................................................................................................
.........................................................................................................................
3 ......................................................................................................................
.........................................................................................................................
[3]
[Total 14 marks]
Andy Todd
28