Coordination & Control – the Nervous System (OCR GCSE Combined Science A (Gateway): Biology)

A 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.

The table shows information about different types of neurons.

(i) Discuss the effect of diameter on the speed of impulse.

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(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.

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A 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.

Explain why it is important that this action is a reflex and not controlled consciously by the brain.

Alzheimer’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.

Speed of diffusion = ........................... metres per second

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(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?

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