# Explain how a nerve impulse is transmitted across a synapse from one neurone to the next.

> Eduqas A-Level Biology — 4.3 Variation and evolution · Explain · 5 marks

## Mark scheme (5 marks)

1. When an impulse arrives at the presynaptic neurone, a neurotransmitter is released into the synaptic cleft
2. The neurotransmitter diffuses across the synaptic cleft
3. The neurotransmitter binds to receptors on the postsynaptic neurone
4. This triggers / generates a new nerve impulse in the postsynaptic neurone
5. The synapse ensures impulses travel in one direction only (because neurotransmitters are released from the presynaptic side and receptors are only on the postsynaptic side)

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level Biology](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-how-a-nerve-impulse-is-7787b584) · Published by Druglandscape Ltd.