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In physiology , an action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a stereotyped trajectory. Action potentials occur in several types of animal cells , called excitable cells , which include neurons , muscle

voltage changes by a large enough amount, an all-or-none electrochemical pulse called an action potential is generated, which travels rapidly along the cell's axon, and activates synaptic connections with other cells when it arrives. Neurons of the adult brain do not generally undergo cell

The lipid bilayer is a thin membrane made of two layers of lipid molecules . These membranes are flat sheets that form a continuous barrier around cells . The cell membrane of almost all living organisms and many viruses are made of a lipid bilayer, as are the membranes surrounding the

on the membranes of the excitable cells, causing the cell to depolarize and trigger an action potential if it is a neuron or a twitch if it is a muscle cell. [ citation needed ] The size and shape of a recorded signal depend upon several factors: the nature of the medium in which the cell

The membrane potential has two basic functions. First, it allows a cell to function as a battery , providing power to operate a variety of "molecular devices" embedded in the membrane. Second, in electrically excitable cells such as neurons , it is used for transmitting signals between different

At a chemical synapse, one neuron releases a neurotransmitter into a small space (the synapse) that is adjacent to another neuron. Neurotransmitters must then be cleared out of the synapse efficiently so that the synapse can be ready to function again as soon as possible. The adult human

An inhibitory postsynaptic potential (IPSP) is a synaptic potential that decreases the chance that a future action potential will occur in a postsynaptic neuron or α-motoneuron. [ 1 ] The opposite of an inhibitory postsynaptic potential is an excitatory postsynaptic potential (EPSP

The relatively static membrane potential of quiescent cells is called the resting membrane potential (or resting voltage), as opposed to the specific dynamic electrochemical phenomena called action potential and graded membrane potential . Apart from the latter two, which occur in excitable