# Describe the pathway of a nerve impulse through a reflex arc when a person's hand touches a sharp object.

> Cambridge International IGCSE Biology (0610) — 14.1 Nervous control in humans · Describe · 4 marks

## Mark scheme (4 marks)

1. The sharp object acts as a stimulus that is detected by receptors in the skin.
2. A nerve impulse travels along the sensory neurone to the spinal cord (CNS).
3. The relay neurone in the spinal cord passes the impulse to the motor neurone.
4. The impulse travels along the motor neurone to an effector (muscle), which responds by contracting to withdraw the hand.

## Key terms

- [reflex arc](https://www.gradenine.co.uk/glossary/reflex-arc)
- [nerve impulse](https://www.gradenine.co.uk/glossary/nerve-impulse)

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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-the-pathway-of-a-nerve-190188b2) · Published by Druglandscape Ltd.