(S6)C14- Response to stimuli

Question 1

Diagram: part of the retina in the human eye

when light falls on cells 1 and 2, only one spot of light is seen. But when light falls on cells 2 and 3, two spots of lights are seen.

Answer 1

• cells 1 and 2 share neurone but 2 and 3 have separate neurones

Question 2

why is it that when cell 3 receives one unit of light energy no light is seen, but when one unit of light energy is received by 3, cells light is seen (3)

Answer 2

• 1 unit of light energy on one cell is below the threshold
• 3 units of light energy is above the threshold so gives sufficient depolarisation
• no impulses in sensory neurone (3>impulses)
• through spatial summation a sufficient neurotransmitter is released

Question 3

cells of the same type as cells 6 and 7 are found in large numbers at the fovea, this results in colour vision with high visual acuity

Answer 3

• cone cells are sensitive to different wavelengths/different frequencies of these waves cause different colours
• Impulses along separate neurone from each receptor cell/each receptor cell connects to separate neurones

Question 4

explain why an increased cardiac output is an advantage during exercise (3)

Answer 4

during exercise:
- more energy is released
- more respiration
- more actively respiring muscles

A higher cardiac output:
- increases O2 supply to muscles
- increases glucose supply to muscles
- lactate removal
- increases heat removal from muscles (for cooling)

Question 5

Explain how nervous control in human can cause increased cardiac output during exercise (4)

Answer 5

• coordination via medulla located in the cardiac centre
• Increased impulses along sympathetic nerve
• to the SA node
• more impulses= increased rate of SA node to increase rate of firing

Question 6

Points A and B show when the atria and ventricles contract at which point was the ventricle contracting and why

Answer 6

B
- 2nd contraction
- occurs immediately after the atrium contraction
- larger more force, more pressure

Question 7

Addition of acetylcholine in the experiment mimics the effect of which branch of the autonomic nervous system

Answer 7

• parasympathetic nervous system

Question 8

If acetylcholine reduces the heart rate and has no effect on the stroke volume. What effect will it have on the cardiac output

Answer 8

• Cardiac output is reduced
• Q= HR x SV
• if heart rate is reduced then so is the cardiac output