[Synaptoarchitectonic structure of muscles as a synchronizing apparatus for muscle contraction]

Synaptoarchitecture is a new notion, refering to the spatial distribution of motor and plates, to the shape of these synapses and to the last ramifications of motor were fibers. In muscles of the rats limbs, endplates are forming a small strip almost perpendicularly to the main direction of muscle fibers. But in sphincters and in orbicular muscles end plates are randomly distributed. The spatial distributions of end plates in muscles of the limbs build up a synchronizer for simultaneous contraction of all fibers in a given muscle. However in some few muscles of the rat, as are the m. sartorius, m. gracilis and mm. glutei, there are many strips, corresponding to the composite structure of these muscles. A composite structure is one which fibers are not only attached to a tendon, but also to other fibers in the midst of the muscle, without any tendon. It is possible to synchronize even a composite structure, if all synapses are properly located, the end plates being all at the same distance from the farthest insertion. In some rodents, lagomorphs and carnivores almost all muscles are composite. Consequently they are all of the disperse type. There is a bunivoque correspondence between the composite structure and the disperse type of innvervation. The shape of motor end plates is changeable under various pathological and physiological circumstances. Beside the common form, there are "myoid" synapses, as may be encountered in myasthenia gravis, in intensive corticotherapy and in the sphincter ani externus. Myoid synapses are of several sorts: elongated, multipartite and minute synapses. For explanation of these various shapes a hypothesis is put forward, concerning structural changes in the postsynaptic membrane. Finally nervous fibers are so located, as to permit the follow up of the pertinent motor endplate, dislocated by muscular contraction.