Structural Features of Chemically Transmitting Synapses

Abstract

Examination by light-microscopy discloses very great diversity in the various types of chemically transmitting synaptic contacts, e.g. the neuromuscular junctions of vertebrates, the various types of synapses in different regions of the central nervous system of vertebrates, the synapses in sympathetic ganglia, the giant synapses in the squid stellate ganglion, the synapses in neuropiles of invertebrates, the synapses of electric organs. The higher order of magnification given by electron-microscopy reveals that in these diverse types of synapse there is a remarkable uniformity in the structures which are believed to be essentially concerned in their functional operation. The review by Couteaux (1961) gives a particularly valuable correlation between structural features and physiological events. It will be convenient firstly to illustrate these features by an account of the vertebrate neuromuscular junction, which has been more thoroughly investigated than any other synapse.