Nerve cells called neurons generate electric signals that pass from one end of the cell to another and release chemical messengers called neurotransmitters to communicate with other cells
Action potentials are large, rapid alterations in the membrane potential. Membranes capable of producing action potentials are called excitable membranes. Examples are membranes in nerve and muscle cells. During an action potential, voltage gated Na+ channels open and allow a large influx of Na+ ions into the cell, making inside of the cell less negative and this is called depolarization. The membrane starts returning rapidly to the resting membrane potential because Na+ channels close, voltage gated K+ channels open, K+ moves out and this is called repolarization.
The potential at which a membrane is depolarized to generate an action potential is called the threshold potential and stimulus that is strong enough to depolarize the membrane is called threshold stimulus.
