The action potential is a rapid and reversible reversal of the electrical potential difference across the plasma membrane of excitable cells such as neurons, muscle cells and some endocrine cells. In a neuronal action potential, the membrane potential rapidly changes from its resting level of approximately -70 mV to around +50 mV and, subsequently, rapidly returns to the resting level again. The neuronal action potential forms an important basis for information processing, propagation, and transmission. In muscle cells, the action potential precedes, and is necessary to bring about, muscle contraction. Some endocrine cells also exhibit action potentials, where the excitation leads to hormone secretion.

The action potential is also referred to as the electrical impulse or nervous impulse.

Graded potential

Neuronal Action Potential

Tastants are taste-provoking chemical molecules that are dissolved in ingested liquids or saliva.

Tastants stimulate the sense of taste. It can also be said that tastants elicit gustatory excitation.

A tastant is the appropriate ligand for receptor proteins located on the plasma membrane of taste receptor cells.