The Generation of Impulses by the Excitatory Postsynaptic Potential and the Endplate Potential

Abstract

Except in rare circumstances, such as with the chick ciliary ganglion (Chapters II, IX), there is at the chemically transmitting synapse a complete break in the cable-like transmission that characterizes propagation along nerve-fibres up to the synapse. Usually the chemical transmission mediates a sequence of events that leads to the postsynaptic generation of a new impulse, as will be described in this Chapter. However, there are many examples of excitatory chemical transmission in which postsynaptic impulses are not generated. The synaptically induced depolarization is adequate in itself either to provide the currents for the discharge of an electric organ such as that of Rata, Astroscopus, Narcine and Torpedo (Grundfest 1957a; Bennett 1961); or to evoke a muscle contraction, as with the slow tonic muscles of the frog (Kuffler and Vaughan Williams 1953; Burke and Ginsborg 1956a, b).