[The functional organization and motor innervation of the cervical skeletal muscle in mammals]

Structural and functional studies have been done on the nerve-muscle transmission in m. biventer cervicis of mouse using electrophysiological, mechanographic and microscopic techniques. It was shown that each muscle fiber has several synaptic inputs, although m. biventer cervicis is a typical phasic skeletal muscle. Usually, there is a single large synapse of the end-plate type and several small synaptic contacts. Some of the synapses investigated produce typical end-plate potential which is transformed into the action potential. Certain part of synapses are capable of producing action potentials only during facilitation of the transmission by rhythmic stimulation. In curarized preparations, supramaximum single indirect stimulus may evoke in a single point of a fiber multicomponent postsynaptic responses of various amplitude and, sometimes, of various latency. Contractile response of a single segment to a maximum direct stimulation is always higher than to an indirect one. Unusual functional properties of m. biventer cervicis are discussed in relation to peculiarities of its origin.