An action potential is a potential change in an excitable tissue or cell that can propagate distally after a suprathreshold stimulus on the basis of the resting potential. Action potential can be composed of depolarization, repolarization, and hyperpolarization. Among these, depolarization is caused by a large and rapid inward flow of sodium ions caused by the opening of a large number of sodium channels, repolarization is caused by a rapid outward flow of potassium ions caused by the opening of potassium channels, and hyperpolarization is caused by the outward flow of potassium ions. Action potentials are characterized by all-or-nothing, non-superimposable, and non-attenuated conduction. Only suprathreshold and threshold stimuli can lead to the generation of an action potential, and the potential cannot be superimposed or summed to produce any condition. Whenever an action potential is generated at any point on the cell membrane, it can be conducted along the cell membrane without change in shape or amplitude.