Excitatory Postsynaptic Potential is generally abbreviated to EPSP. Impulses are transmitted from neuron to neuron by the release of a chemical transmitter across synaptic clefts from the synaptic vesicles along the axon to the postsynaptic receptors of another neuron. An EPSP has the effect of depolarizing a neuron and the IPSP has the effect of hyperpolarizing it.
Much information is available under the heading synapse, but this is a different concept.
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