# Explain how a reflex arc protects the body from harm, referring to the role of neurones involved and the speed of the response.

> Edexcel GCSE Biology (1BI0) — 2.3 The nervous system · Explain · 4 marks

> A student accidentally touches a hot surface and quickly pulls their hand away before they are consciously aware of the pain.

## Mark scheme (4 marks)

1. Sensory neurones carry the nerve impulse from the receptor to the central nervous system (spinal cord)
2. Motor neurones carry the nerve impulse from the CNS to the effector (muscle), causing a response
3. The reflex arc bypasses the brain / does not involve conscious processing, so the response is faster
4. The faster response means the hand is withdrawn before significant tissue damage occurs, protecting the body from harm

## Key terms

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

## Related

- [Revision notes for Edexcel GCSE Biology (1BI0)](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-protects-30834be6) · Published by Druglandscape Ltd.