Studies on Impulse Conduction of Nerve Fibers

Abstract

Excitation of nerve fibers is conducted as an electrical impulse, namely, the pulse of action current generated on the basis of the conformational change of ionic channels. As early as in the mid-19th century, by constructing a sensitive galvanometer, E. du Bois-Reymond succeeded in recording a steady negative current from the cut end to the intact portion of a frog nerve (injury current). When he excited the nerve with a current from the stimulating electrode, he observed that the injury current was neutralized. He called the current change evoked by nerve stimulation a “negative variation.” The former phenomenon shows that the cut end of nerve fibers (to be equal to the inside of the nerve axons) is electrically negative to the intact region of nerve fibers, and the latter shows that in the excited point of the nerve fibers occurs a negative electrical change, which neutralized the negative injury current. The two phenomena were actually considered to be the discoveries of the resting membrane potential as well as the action potential that is generated during excitation of nerve fibers (see Tasaki 1982, pp. 9–10).