General Properties of Intercellular Communication in the Nervous System

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, cardiac and smooth) 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 and is essential for nerve cells with axons more than a few millmetres in length. However, as we shall see, impulses are not necessary for communication between neurons: many small neurons communicate without being able to generate action potentials, and many neurons that do propagate action potentials along their axons communicate with other nerve cells, especially via their dendrites, by mechanisms that may generate graded potential changes rather than all-or-nothing events.