Describe an action potential.

A stimulus excites a neuron by causing the opening of sodium channels.
This causes an influx of sodium which causes the opening of other voltage-gated sodium channels.
This causes the membrane to depolarise to threshold. 
Depolarisation is followed by hyperpolarisation where potassium ions leave the cell. 
This returns the membrane to resting potential. 

Answered by Maciek K. Biology tutor


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