Repolarization

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Repolarization is a term from cell physiology and specifically describes the return of the membrane potential on an axon to the resting potential after a depolarization . Instead, the general term hyperpolarization can also be used, the subsequent phase then being designated as post-hyperpolarization.

After the depolarization, the voltage-activated sodium channels first become impermeable to sodium ions again by closing the inactivation gates, which means that there is no further increase in the membrane potential.

There are also voltage-activated potassium channels in the axon membrane , which now open. This leads - the concentration gradient following - a strong outflow of potassium - ions . As a result, the external medium is again enriched with positive charge carriers, while they decrease inside. The membrane potential consequently drops again and after a brief hyperpolarization (alternatively post-hyperpolarization ) returns to the resting potential.

The original ion distribution of the resting potential (many sodium ions on the outside and many potassium ions on the inside) is then restored by the sodium-potassium pump and the activation gates of the voltage-dependent sodium channels are also closed.

A new action potential can only be triggered again when the inactivation gates of the voltage-dependent sodium channels are opened again. This refractory period is usually around 2 ms.