The three stages of Action Potential are: 1. depolarization- Na+ channels open up inside of the membrane and becomes more positive than the RMP. 2. repolarization- The Na+ channels inactivating and K+ channels opening AP spike stops rising to which the membrane returns to RMP. 3. hyperpolarization- A few of the K+ channels remain open and the Na+ channels reset inside of membrane becomes more negative than RMP.
