# Describe the pathway of a reflex action, from detection of a stimulus to the response of an effector.

> AQA GCSE Biology (8461) — 4.5.2 The human nervous system · Describe · 4 marks

## Mark scheme (4 marks)

1. Receptors detect the stimulus
2. Electrical impulse travels along a sensory neurone to the CNS (spinal cord)
3. The impulse passes through a relay neurone in the spinal cord
4. Impulse travels along a motor neurone to an effector (muscle or gland), which produces the response

## Key terms

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

## Related

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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-the-pathway-of-a-reflex-a046f120) · Published by Druglandscape Ltd.