# Describe how a reflex arc works to produce a rapid response when a person touches a very hot object, naming each component involved in the pathway.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 4.3 Nervous system and reflex action · Describe · 5 marks

> Reflex actions are automatic, rapid responses to stimuli that help protect the body from harm. They do not involve conscious thought.

## Mark scheme (5 marks)

1. A receptor in the skin detects the stimulus (heat/pain)
2. A sensory neurone carries the impulse from the receptor to the spinal cord / central nervous system
3. A relay neurone in the spinal cord connects the sensory neurone to the motor neurone
4. A motor neurone carries the impulse from the spinal cord to the effector (muscle)
5. The effector (muscle) responds by contracting so the hand is withdrawn / moved away from the heat

## Key terms

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

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-how-a-reflex-arc-works-7736b9d5) · Published by Druglandscape Ltd.