# Explain how the release of a neurotransmitter at a cholinergic synapse leads to the generation of a new action potential in the postsynaptic neurone.

> IB DP Biology Higher Level (2023 syllabus) — C2.2 Neural signalling · Explain · 4 marks

## Mark scheme (4 marks)

1. An action potential arriving at the presynaptic terminal causes depolarisation, triggering voltage-gated calcium ion channels to open.
2. Calcium ions cause synaptic vesicles containing acetylcholine to fuse with the presynaptic membrane and release acetylcholine into the synaptic cleft by exocytosis.
3. Acetylcholine diffuses across the synaptic cleft and binds to specific receptors on the postsynaptic membrane.
4. Receptor binding causes ligand-gated sodium ion channels to open, allowing Na⁺ influx that depolarises the postsynaptic membrane; if threshold is reached, a new action potential is generated.

## Key terms

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

## Related

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-release-of-a-d836abdd) · Published by Druglandscape Ltd.