The refractory period in a neuron occurs after an action potential and generally lasts one millisecond.

What causes the refractory period?

Refractory periods are caused by the inactivation gate of the Na⁺ channel. Once inactivated, the Na⁺ channel cannot respond to another stimulus until the gates are reset.

What happens during the refractory period of a neuron?

In its wake, the action potential leaves the Na⁺ channels inactivated and K⁺ channels activated for a brief time. These transitory changes make it harder for the axon to produce subsequent action potentials during this interval, which is called the refractory period.