Neuromuscular transmission (NMT) is a process that permits the central nervous system to control the movement of muscles in the body. Nerve impulses cause the release of a neurotransmitter, acetylcholine (ACh), into the junction between the nerve cell and the muscle cell. Diseases involving the neuromuscular junction are called NMT disorders because they are caused by a dysfunction in the transmission of ACh at the nerve–muscle synapse. Depending on the site of dysfunction, NMT disorders are classified into three distinct groups: postsynaptic disorders, presynaptic disorders, and combined presynaptic and postsynaptic disorders. Neuromuscular transmission block due to an injury of the peripheral nerve appears in the early stages of reinnervation. In microelectrode methods, miniature end-plate potentials (MEPPs) were of normal amplitude but of decreased frequency. The quantum content of the end-plate potential (EPP) decreased significantly, while the quantum size of the EPP was within normal limit. The time course of the EPPs was remarkably prolonged despite the normal time course of MEPPs. Abnormal end-plate responses returned to normal after day 40. Neuromuscular transmission block in the early stages of reinnervation could best be explained by a failure of impulse to invade the axon terminal and by the decreased number of acetylcholine (ACh) quanta readily available for release from the nerve terminals. It is likely that the metabolism of ACh and calcium ions is not appropriate in immature nerve terminals.
Relevant Topics in Neuroscience & Psychology
