- Potential- In physiology, an action potential occurs when the membrane potential of a specific axon location rapidly rises and falls: this depolarisation then causes adjacent locations to similarly depolarise.

As an action potential (nerve impulse) travels down an axon there is a change in polarity across the membrane of the axon. In response to a signal from another neuron, sodium- (Na+) and potassium- (K+) gated ion channels open and close as the membrane reaches its threshold potential. Na+ channels open at the beginning of the action potential, and Na+ moves into the axon, causing depolarization. Repolarization occurs when the K+ channels open and K+ moves out of the axon, creating a change in polarity between the outside of the cell and the inside. The impulse travels down the axon in one direction only, to the axon terminal where it signals other neurons.

Propagation- In neurons, action potentials play a central role in cell-to-cell communication by providing for—or, with regard to saltatory conduction, assisting—the propagation of signals along the neuron's axon towards synaptic boutons situated at the ends of an axon; these signals can then connect with other neurons at synapses, or