[Phenomenon of active reorganization of the architectonics (structure) of motor units]

The density of muscle fibers in a motor unit (MU) was studied electromyographically with the aid of a microelectrode. Muscle biopsy specimens withdrawn from patients with different neuromuscular diseases were subjected to morphological and histochemical studies. During denervation-reinnervation processes, the motoneuron actively reconstitutes the structure of an innervated MU. Apart from branching in the central part, the motoneuron excludes from the innervation zone the muscle fibers located in the most remote areas in respect of the MU center.