A Second Motor Nerve System to Frog Skeletal Muscle

Abstract

A separate small-nerve motor system to frog''s skeletal muscles is described. Small diam. motor nerve fibres evoke local potentials and local shortening at the region of the nerve-muscle junction in contrast to the well known twitch responses associated with propagated muscle impulses. The small nerve fibre system can be stimulated exclusively after elimination of the large diam. fibres from nerve trunks (a) by progressive pressure block or galvanic block, (b) by cutting all but a desired small nerve fibre, (c) by reflex stimulation. The small nerve fibre system is active reflexly in spinal or lightly anesthetized prepns. Appreciable muscle tension without the appearance of twitch responses may be set up.