# Describe the roles of sensory neurones, the central nervous system (CNS), and motor neurones in producing a response to a stimulus.

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

> A student accidentally touches a hot pan. Within a fraction of a second, the student pulls their hand away.

## Mark scheme (4 marks)

1. A sensory neurone carries nerve impulses from the receptor to the CNS (brain and/or spinal cord).
2. The CNS (brain and/or spinal cord) processes/coordinates the information.
3. A motor neurone carries nerve impulses from the CNS to the effector.
4. The effector (muscle/gland) produces the response, e.g. the muscle contracts to pull the hand away.

## Key terms

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

## Related

- [Revision notes for Edexcel GCSE Biology (1BI0)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-the-roles-of-sensory-neurones-79413fc7) · Published by Druglandscape Ltd.