# Explain the roles of the sensory neurone, relay neurone, and motor neurone in transmitting a nerve impulse through the central nervous system (CNS) to produce a response.

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

> A student pricks their finger on a drawing pin. The nervous system rapidly coordinates a response without the student having to think about it.

## Mark scheme (4 marks)

1. The sensory neurone carries the impulse from the receptor to the CNS (brain or spinal cord).
2. The relay neurone connects the sensory neurone to the motor neurone within the CNS.
3. The motor neurone carries the impulse from the relay neurone to the effector.
4. The effector (muscle or gland) produces a response, such as the muscle contracting to withdraw the finger.

## Key terms

- [sensory neurone](https://www.gradenine.co.uk/glossary/sensory-neurone)
- [relay neurone](https://www.gradenine.co.uk/glossary/relay-neurone)
- [motor neurone](https://www.gradenine.co.uk/glossary/motor-neurone)
- [central nervous system (CNS)](https://www.gradenine.co.uk/glossary/central-nervous-system-cns)

## 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-the-roles-of-the-sensory-ee57cdb3) · Published by Druglandscape Ltd.