Mononeuronal double innervation of an amphibian striated muscle fibre.

Abstract

1) To ascertain that a single skeletal muscle fibre can have double terminals from branches of a single nerve fibre, experiments were done on preparations of the frog's whole sartorious muscle:(a), on a preparation of a fibre bundle obtained by reducing muscle fibres (b) and also on a preparation of a single muscle fiber connected with a single nerve fibre (c).2) The ocurrence of this mononeuronal double innervation of an individual muscle fibre was clearly demonstrated in this experiment by examining the pictures of the spike potential which were taken at one end of the muscle before and after cutting one or more of branches innervating the muscle.3)(a) showed that double innervation by the same nerve fibre occurs in numbers of muscle fibres in the whole muscle.(b) showed that mononeuronal double innervation occurs by various branchings of a nerve fibre.Furthermore (c) showed most clearly the mononeuronal double innervation and from this the distance between two junctions was estimated.4) Physiological significances of mononeuronal double innervation were considered in comparison with polyneuronal one. A size of motor unit may be different according to its mononeuronal or polyneuronal double innervation.Rapidity and gradation of contraction are also somewhat different between the two.