Action potential

Action potential

Depolarization

Hyperpolarization

If a threshold voltage is reached at the axon hillock, voltage-gated Na channels open and initiate an action potential.

K+ outflow causes the voltage to drop back into the negative range, slightly overshooting the original resting membrane potential (RMP).

Local potential

Na+ inflow causes a rapidly rising voltage. Na+ channels begin to close at 0 mV, but the voltage typically reaches about +35 mV by the time all of them close.

Repolarization

Resting membrane potential

Stimulation of the neuron creates a gradually rising local potential.

Threshold