# Explain how myelination of a neuron affects the speed of action potential propagation along its axon.

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

## Mark scheme (4 marks)

1. Myelin sheath is an insulating layer formed by Schwann cells wrapped around the axon
2. Ion exchange / depolarisation can only occur at nodes of Ranvier (gaps between myelin sheaths)
3. The action potential 'jumps' between nodes of Ranvier (saltatory conduction), bypassing the myelinated internodes
4. Saltatory conduction increases the speed of propagation compared with unmyelinated axons, because less membrane needs to be depolarised

## Key terms

- [action potential propagation](https://www.gradenine.co.uk/glossary/action-potential-propagation)

## Related

- [Revision notes for IB DP Biology Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-myelination-of-a-neuron-f47cad3c) · Published by Druglandscape Ltd.