THE INTERPRETATION OF THE ACTION POTENTIAL IN CUTANEOUS AND MUSCLE NERVES

Abstract

Comparison of the fiber-size patterns with the action potentials in muscular and cutaneous branches of the dog''s femoral nerve and in skin nerves of the bullfrog confirms the direct relationship between fiber diam. and conduction rate and the determination of action potential configuration by the histology of the nerve. Corresponding with the 4 waves in the action potential of a mixed nerve there are 4 aggregations in the continuous range of fibers, of which 3 are myeli-nated. Of the branches of the femoral nerve, those supplying voluntary muscle exhibit one very definite pile of fibers, which form the sole visible wave (alpha) in their action potentials, and 3 indefinite accumulations (if unmyelinated fibers be included); the branch supplying the skin exhibits 3 cumuli and the corresponding waves, namely, beta, gamma, and delta. The alpha fibers convey motor and muscle-sense impulses. The delta sensory fibers (probably unmyelinated) presumably mediate pain. The beta and gamma fibers would then be left for the mediation of touch and temp. impulses.