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In muscle cells, for example, an action potential is the first step in the chain of events leading to contraction. In other types of cells, their main function is to activate intracellular processes. In neurons, action potentials play a central role in cell–cell communication by providing for-or with regard to saltatory conduction, assisting-the propagation of signals along the neuron's axon toward synaptic boutons situated at the ends of an axon these signals can then connect with other neurons at synapses, or to motor cells or glands. Certain endocrine cells such as pancreatic beta cells, and certain cells of the anterior pituitary gland are also excitable cells. Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and in some plant cells. This depolarization then causes adjacent locations to similarly depolarize. The impulse travels down the axon in one direction only, to the axon terminal where it signals other neurons.Īn action potential occurs when the membrane potential of a specific cell rapidly rises and falls. Repolarization occurs when K + channels open and K + moves out of the axon, creating a change in electric polarity between the outside of the cell and the inside. Na + channels open at the beginning of the action potential, and Na + moves into the axon, causing depolarization. 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. Neuron communication by electric impulsesĪs an action potential (nerve impulse) travels down an axon there is a change in electric polarity across the membrane of the axon.