What are the stages of an action potential?

Stimulus arrives and changes membrane polarity to the threshold to elicit an action potential (all or nothing nature). Depolarisation- sodium ion channels open increasing the membrane polarity Repolarisation- sodium ion channels close and potassium ion channels open which then diffuse into the cell decreasing the membrane polarity again. Hyperpolarisation- The membrane polarity has returned to normal and the potassium ion channels shut, however there is a slight delay so membrane polarity continues to decrease past the resting value. The sodium-potassium pump on the cell membrane is then used to return the membrane polarity to rest.