# Define the term 'synapse' and explain how a nerve impulse is transmitted across one.

> WJEC GCSE Biology (Wales) — 2.5.1 The nervous system · Define and Explain · 4 marks

## Mark scheme (4 marks)

1. A synapse is a junction/gap between two neurones (or between a neurone and an effector/receptor)
2. A nerve impulse arriving at the synapse causes the release of a chemical (neurotransmitter) from the presynaptic neurone
3. The neurotransmitter diffuses across the synaptic gap
4. The neurotransmitter binds to receptors on the postsynaptic neurone, generating a new nerve impulse

## Key terms

- [synapse](https://www.gradenine.co.uk/glossary/synapse)
- [nerve impulse](https://www.gradenine.co.uk/glossary/nerve-impulse)

## Related

- [Revision notes for WJEC GCSE Biology (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Define and 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/define-the-term-synapse-and-explain-72e25da7) · Published by Druglandscape Ltd.