When Do Sodium Channels Inactivate?

Voltage-gated sodium channels open (activate) when the membrane is depolarized and close on repolarization (deactivate) but also on continuing depolarization by a process termed inactivation, which leaves the channel refractory, i.e., unable to open again for a period of time.

Why do sodium channels inactivate?

This increase in voltage constitutes the rising phase of an action potential. At the peak of the action potential, when enough Na⁺ has entered the neuron and the membrane's potential has become high enough, the Na⁺ channels inactivate themselves by closing their inactivation gates.

At what voltage do sodium channels close?

Typically, sodium channels are in a resting or “closed” state in neurons or muscle cells that are at rest (with a membrane potential of approximately −60 to −80 mV). Closed sodium channels do not conduct sodium ions, but are ready to be activated or “opened” when stimulated by membrane depolarization.