1
2 marks
2 marksComplete the sequence of a reflex arc.
| Stimulus → | ........................... |
Sensory neurone → |
CNS → | ........................... ........................... |
Effector → | Response |
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3.1 Coordination & Control – the Nervous System
2a5 marks
5 marksA boy picks up a hot plate and quickly drops it.
This is a reflex action.
Describe the sequence of events that happens in his nervous system during this reflex action.
2b4 marks
4 marksThe table shows information about different types of neurons.
| Type of neurone | Is myelin sheath present? |
Diameter (× 10–3 mm) |
Speed of impulse (m/s) |
| A | yes | 13–20 | 80–120 |
| B | yes | 6–12 | 33–75 |
| C | yes | 5–8 | 4–24 |
| D | yes | 1–5 | 3–15 |
| E | no | 0.2–1.5 | 0.5–20 |
(i)
Discuss the effect of diameter on the speed of impulse.
[2]
(ii)
Explain how strong a conclusion, if any, you can make from the data about the effect of the myelin sheath on the speed of impulse.
[2]
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3a5 marks
5 marksA boy picks up a hot plate and quickly drops it.
This is a reflex action.
Describe the sequence of events that happens in his nervous system during this reflex action.
3b3 marks
3 marksExplain why it is important that this action is a reflex and not controlled consciously by the brain.
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45 marks
5 marksAlzheimer’s disease involves damage to nerve transmission.
Symptoms include difficulties in judging distance, concentrating and making decisions.
The diagram shows a synapse between two neurones in the brain.
Acetylcholine is a neurotransmitter in the brain. It diffuses across the 32 nanometre synaptic gap.
In a brain from a person with Alzheimer’s disease, the time for acetylcholine to diffuse between neurones is 6.4 × 10–7 s.
1 metre = 109 nanometres
(i)
Calculate the speed of diffusion in a person with Alzheimer’s disease.
Use this formula: speed = distance ÷ time
Give your answer in metres per second.
Use this formula: speed = distance ÷ time
Give your answer in metres per second.
Speed of diffusion = ........................... metres per second
[3]
(ii)
In the brain of a healthy person the speed of diffusion is 0.2 metres per second.
How does the result obtained in part (i) account for the symptoms of Alzheimer’s disease?
How does the result obtained in part (i) account for the symptoms of Alzheimer’s disease?
[2]
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