5.1.5 Animal Responses

Question 1

What is the role of the central nervous system?

Answer 1

Co-ordination of impulses

Question 2

What is the role of peripheral nervous system?

Answer 2

Sensing stimuli from environment and controlling the effectors’ response

Question 3

What is the functional organisation of the nervous system?

Answer 3

Somatic and Autonomic

Question 4

What is the function of the somatic nervous system?

Answer 4

Under conscious control of voluntary motor movements and processing sensory stimuli
Carries impulses to muscle

Question 5

What is the function of the autonomic nervous system?

Answer 5

Subconscious control - automatic movements.

Carries impulses to glands, smooth muscle and cardiac muscle

Question 6

Describe the neurones in the parasympathetic nervous system

Answer 6

Long pre-ganglionic neurone
Short post-ganglionic neurone
Releases acetylcholine at neurotransmitter

Question 7

Describe the neurones in the sympathetic nervous system

Answer 7

Short pre-ganglionic neurone
Long post-ganglionic neurone
Releases noradrenaline at neurotransmitter

Question 8

Describe the gross structure of the brain

Answer 8

Protected by skull and surrounded by meninges (protective membranes)

Question 9

What are the five main areas of the brain?

Answer 9

1. Cerebrum
2. Medulla oblongata
3. Cerebellum
4. Hypothalamus
5. Pituitary gland

Question 10

Describe, and state the function of, the cerebrum

Answer 10

Structure: The main part of the brain (split into 2 hemispheres) - highly convoluted, with an outer lining (cerebral cortex).
Function: co-ordinates voluntary, and some involuntary, movements. Different areas receive sensory input from receptors in sense organs and pass on info to association areas

Question 11

State the function of the cerebellum

Answer 11

Co-ordinates muscular movement, balance and posture. Receives input from ears and muscles & tendons, then relays to the motor cortex in cerebrum

Question 12

State the function of the medulla oblongata

Answer 12

Contains many regulatory systems (e.g. blood glucose conc) that control involuntary actions. Also involved in control of voluntary movements and relaying signals to CNS

Question 13

State the function of the hypothalamus

Answer 13

Main controlling region for the ANS - has two centres for parasympathetic and sympathetic systems.

1. Controls complex behaviours (e.g. sleeping, eating)
2. Monitors contents of blood (glucose conc)
3. Produces hormones

Question 14

State the function of the pituitary gland

Answer 14

Controls most glands in the body, divided into 2 sections:
Anterior - produces hormones involved in growth, sexual development and skin pigmentation e.g. FSH
Posterior - stores and releases hormones made in hypothalamus - ADH, Oxytocin

Question 15

State and describe an example of a spinal reflex

Answer 15

Knee Jerk: 1) Tap causes patellar tendon to stretch
2) Reflex arc occurs - extensor muscle on top of thigh contracts whilst flexor muscle relaxes
3) Leg kicks
For maintaining balance and posture

Question 16

State and describe an example of a cranial reflex

Answer 16

Blinking: 1) Cornea irritated (touch) - triggers impulse to lower brain stem
2) Impulse initiates closing of eyelids (consensual response - both eyelids close)
Reflex indicates functioning of lower brain stem

Question 17

What is the survival value of reflexes?

Answer 17

1. They’re involuntary - brain can focus on complex responses
2. Present from birth - immediate protection
3. Extremely fast
4. Many control everyday actions - e.g. staying upright and digestion

Question 18

Describe the fight/flight response in response to acute stress

Answer 18

1. Hypothalamus activates SNS
2. Uses neuronal pathways to activate glands/smooth muscle (nervous) or activates adrenal medulla (hormonal)
3. Release of adrenaline and noradrenaline from adrenal medulla

Question 19

Describe the fight/flight response in response to chronic stress

Answer 19

1. Hypothalamus activates adrenal-cortical system through release of CRF
2. Pituitary gland secretes ACTH
3. ACTH triggers release of 30 hormones at adrenal cortex

Question 20

Describe the second messenger model of adrenaline

Answer 20

1. Adrenaline binds to receptor site on target cell membrane - activates adenylyl cyclase
2. Enzyme triggers ATP conversion to cAMP
3. Increase in cAMP activates protein kinases that activate more enzymes (cascade effect)

Question 21

Explain the hormonal control of heart rate

Answer 21

Stress hormones (adrenaline and noradrenaline) increase the heart rate by increasing frequency of impulses by SAN

Question 22

Explain the nervous control of heart rate

Answer 22

Two centres in Medulla Oblongata: One INCREASES heart rate - impulse to SNS via accelerator nerve
One DECREASES heart rate - impulse to PNS via vagus nerve

Question 23

What are chemoreceptors? Explain their role in controlling heart rate.

Answer 23

Receptors sensitive to chemical changes e.g. pH. Located in carotid artery, aorta and medulla.
CO2 levels INCREASE - pH DECREASE - MORE impulses to medulla oblongata and for SAN stimulation
CO2 levels DECREASE - pH INCREASE - LESS impulses for SAN stimulation and to medulla oblongata

Question 24

What are baroreceptors?

Answer 24

Receptors sensitive to (blood) pressure changes.
Located in carotid artery, aorta and vena cava.
BP INCREASE - reduced frequency of SAN stimulation
BP DECREASE - greater frequency of SAN stimulation

Question 25

Describe the structure of skeletal muscle

Answer 25

Striated, multi-nucleated muscle fibres bundled together, surrounded by plasma membrane (sarcolemma). Muscle fibres made up of myofibrils (made up of actin and myosin filaments). Shared cytoplasm is sarcoplasm. Parts of sarcolemma fold in to form T tubules to help spread impulses through sarcoplasm at same time

Question 26

What is the function of skeletal muscle?

Answer 26

Conscious control of voluntary muscle | Responsible for locomotion

Question 27

Describe the structure of cardiac muscle?

Answer 27

Specialised striated, uni-nucleated fibres - cells branch and interconnect for simultaneous contraction. Much fainter striations than skeletal muscle

Question 28

What is the function of cardiac muscle?

Answer 28

Maintain involuntary regular heart rate (myogenic)

Question 29

Describe the structure of involuntary (smooth) muscle

Answer 29

Non-striated, uni-nucleated, spindle shaped fibres - no regular arrangement.

Question 30

What is the function of involuntary (smooth) muscle?

Answer 30

Allow for control of essential mechanisms without conscious thought, e.g. peristalsis, breathing (blood vessel walls)

Question 31

What is the difference between slow and fast twitch muscle?

Answer 31

Slow - uses oxygen as fuel for continuous contractions e.g. legs Fast - uses anaerobic metabolism for fuel - appear less red than slow twitch e.g. eyelids

Question 32

What are some similarities between the action of synapses and neuromuscular junctions?

Answer 32

1. Release neurotransmitters across synaptic gap | 2. Enzymes present that break down neurotransmitter

Question 33

What are some differences between the action of synapses and neuromuscular junctions?

Answer 33

1. Neuromuscular junctions have more receptors on post-synaptic membrane 2. Action potential from neuromuscular junction always triggers a response, synapse could be inhibitory 3. Neuromuscular junction causes muscular contraction, synapse causes nerve impulse 4. One muscle fibre for each neuromuscular junction, but synapses could provide neurotransmitters to multiple post-synaptic neurones

Question 34

Describe the action of neuromuscular junctions

Answer 34

1. Acetylcholine released by synaptic vesicles into synaptic cleft - binds to receptors on sarcolemma of muscle fibre 2. Binding causes opening of Na+ channels - depolarises muscle fibre, spreads along sarcolemma and down T-tubules 3. Action potential triggers release of Ca2+ from sarcoplasmic reticulum 4. Acetylcholine esterase breaks down acetylcholine into choline and acetyl (ethanoic acid) - diffuse back into neurone

Question 35

Describe the sliding filament model

Answer 35

1. Without enough Ca2+ present, tropomyosin blocks actin binding sites - myosin head can't attach 2. Ca2+ (released from sarcoplasmic reticulum) binds to troponin - changes tertiary structure, resulting in tropomyosin not blocking the binding site 3. ATP is bound to myosin - hydrolyses to ADP and Pi for energy for 'cocked' positioning of head 4. Cross-bridges form between actin and myosin head 5. Release of Pi causes conformational change in head - moves actin along (power stroke) 6. ADP released, ATP binds to myosin head - detaches from binding site 7. ATP hydrolysed to ADP and Pi, so head moves back to original position

Question 36

What occurs when the stimulation of the muscle stops?

Answer 36

Without the release of acetylcholine, Ca2+ is transported back into the sarcoplasmic reticulum. Tropomyosin blocks active sites again

Question 37

How does creatine phosphate maintain the ATP supply?

Answer 37

Acts as a reserve of Pi - binds with ADP to form ATP and creatine. Only for short bursts of vigorous exercise - store used up quickly. Replenished when relaxed - Pi from ATP hydrolysis

Question 38

What are the sources of creatine phosphate?

Answer 38

1. Meat | 2. Internal production by liver and kidneys

Question 39

What changes occur in the sarcomere when contracted?

Answer 39

H zone narrows Dark (A) band remains the same, Light (I) band shortens Z lines are closer together

Question 40

What's the difference between actin and myosin's connection to the Z line?

Answer 40

Actin connects directly to Z line | Titin molecules connect myosin to Z-line