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Explain the difference in the speed of conduction of an action potential along the length of a myelinated neurone and a non-myelinated neurone.

First, we need to explain how the action potential is conducted along the length of the axon.

An action potential is transferred along an axon by the movement of Na+ and K+ ions into and out of the cell. These are controlled by voltage-gated Naand K+ channels. 

When the neuron is stimulated, the voltage-gated Na+ ion channels open, causing Na+ ions to flood into the cell. There is a positive charge inside the cell and a negative charge outside.

This change in charge causes K+ channels to open and Na+ channels to close. K+ ions diffuse out and the charge builds up so that there is a positive charge outside the cell and a negative charge inside.

This change in charge again causes the Na+ channels to open and the K+ channels to close. This occurs like a wave along the length of the axon and the signal travels away.

We also need to look at the soidum potassium pump. In an non-myelinated neuron these will occur along the entire length of the axon. Whereas, in a myelinated neuron, these occur in the gaps between Schwann cells which coat the axon.

In myelinated neurons this will occur by 'saltatory conduction' - so the action potential jumps between neurons. You can think of this like skipping, the signal travels faster by jumping a bit.

Catherine H. GCSE Biology tutor, A Level Biology tutor, IB Biology tu...

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