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motor endplate


Definition: the large and complex end formation by which the axon of a motor neuron establishes synaptic contact with a skeletal muscle fiber (cell); several terminal branches of a motor axon end in irregular, club-shaped synaptic end formations, each of which is bedded in its own troughlike depression of the muscle fiber's surface; the postsynaptic membrane, the sarcolemma that forms the bottom of the trough, is greatly increased in surface area by deep infoldings protruding into the underlying cytoplasm of the muscle fiber; the subsynaptic interval between the plasma membrane of the axon terminals and the sarcolemma is filled with an amorphous substance; the trough is closed off toward the surface by the Schwann sheath, which peels away from the axons as the latter enter the trough and thus forms a lid over the trough; the slight bulge of this closure plate corresponds to Doyère eminence.

Synonym(s): sole-plate ending

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© Copyright 2018 Wolters Kluwer. All Rights Reserved. Review date: Sep 19, 2016.