Answer:
calcium channel close.
Explanation:
In action potential there is phase 0, phase 1, phase 2, phase 3 and phase 4. In phase 3 of action potential there is a rapid repolarization phase in which calcium channels remain closed but potassium channels remain open and continuous outward movement or leakage of positive ions causes the outside environment positive and membrane potential goes to negative charge that is -85mV to -90mV
