General Properties of Synaptic Transmission

Abstract

As mentioned in Chapter 1, the prime function of nervous systems is one of communication: communication within the organism itself and with the external environment, including communication with other organisms. Furthermore, the individual nerve cells that make up the nervous system communicate with one another and with a variety of cells (effector cells) that carry out the nervous system’s commands. These effector cells include, muscle cells (striated, smooth and cardiac) and a variety of secretory (gland) cells. The nerve impulse is a mechanism whereby these commands may be sent quickly from one end of a nerve cell to the other. In general, there is no cytoplasmic continuity between individual nerve cells or between nerve cells and effector cells. This is the neuron doctrine of Ramon y Cajal, which, in turn, is the cell theory of Schleiden and Schwann applied to the nervous system. Neurons contact one another at synapses (a term coined by Sherrington) or they contact muscle cells at neuromuscular junctions and gland cells at neuro-glandular junctions. It is a convenient shorthand, which has become common usage, to call all these contacts “synapses”.