Dictionary of Biological Psychology
excitatory postsynaptic potential
(EPSP) A DEPOLARIZATION of a NEURON due to input at a SYNAPSE from an excitatory neurotransmitter (see NEUROTRANSMITTERS).
EPSPs are local potentials that decay with distance and can summate with other EPSPs and IPSPS that are occurring in the same cell (SPATIAL SUMMATION). They have a slow time course, relative to that of an ACTION POTENTIAL, and therefore show TEMPORAL SUMMATION when repeated inputs occur across the same synapse. Specialized EPSPs, such as at the NEUROMUSCULAR JUNCTION, can be large enough to always lead to an action potential, but in the CENTRAL NERVOUS SYSTEM virtually all EPSPs are too small to reach THRESHOLD without summation.
DOUGLAS D.RASMUSSON
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