# Explain how a reflex arc allows the body to respond rapidly to a harmful stimulus, naming the structures involved in the pathway.

> OCR GCSE Biology A: Gateway Science (J247) — B3.1 Coordination and control — the nervous system · Explain · 4 marks

> A student accidentally touches a very hot surface and quickly pulls their hand away before they are consciously aware of the pain. This is an example of a reflex action.

## Mark scheme (4 marks)

1. A receptor detects the stimulus (heat/pain) and generates a nerve impulse
2. The impulse travels along a sensory neurone to the spinal cord / CNS
3. A relay neurone (in the spinal cord) passes the impulse to a motor neurone
4. The motor neurone carries the impulse to an effector (muscle) which produces a response (hand pulls away) / the reflex bypasses the brain making it faster

## Key terms

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

## Related

- [Revision notes for OCR GCSE Biology A: Gateway Science (J247)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-a-reflex-arc-allows-9207de06) · Published by Druglandscape Ltd.