Peripheral Coding in the Nervous System

This chapter discusses the nature of the nerve message and compares it to a telephone message that is transmitted by telegraphing it in Morse code—or through a series of clicks. As with nerve messages, a series of “clicks” is, in fact, all the brain ever receives from the nerves. Telephone wires are different, however, from nerves in that nerves are made not of metal but of dilute salt solution. Nerve signals need boosting every l mm, and the anatomical continuity of the nerve fiber is, in fact, interrupted every 1 mm by a “node of Ranvier,” which electrophysiology has shown to be a boosting station. If the telephone message is to preserve its quality, each node should restore to the signal exactly what was lost in traveling along the cable from the last node. The minutest fluctuation, therefore, from a perfect restoration will result in a signal that is either all or none.