Depolarization

When depolarizing stimuli reach threshold level, voltage gated Na⁺ channels open and Na ⁺ influx into cell. This influx of Na ⁺ into cell result opening of more and more voltage gated Na⁺ channels (positive feedback mechanism). Therefore Na⁺ ion accumulate inside the nerve cell and membrane potential become positive.

Repolarization

In this stage voltage, voltage gated Na+ channels close and voltage gated K+ channels open and K efflux. This opening is slower and more prolonged than the opening of the Na⁺ channels. The cell membrane repolarize due to efflux of K + ion .

After-hyperpolarization

The K⁺ channels close slowly it result after-hyperpolarization followed by a return to the resting membrane potential