Action potential comprises of four major stages Depolarization Repolarization Hyperpolarization Resting potential As the stimulus arrives the sodium channel opens and the axon becomes depolarized. As depolarization moves down the axon the previous part of the axon that was depolarized is repolarized as sodium gates are closed and the potassium channel opens. In this mean time axon cannot be depolarized. Action potential goes along the axon with the wave of depolarization and repolarization until it reaches the synapse.