An area of membrane between a motoneuron and the membrane plasma of a muscle (i.e., the motor end plate) that forms a synapse between them that ramifies into a number of fine branches with terminal swellings called synaptic boutons. The boutons lie over the motor end plates, and they are separated by a synaptic cleft. Each skeletal muscle fiber typically receives one terminal branch of a motoneuron. A nerve impulse traveling down the axon creates small depolarizations in the end plate at a critical threshold, which results in the release of the neurotransmitter acethycholine into the synaptic cleft and in turn the production of an excitatory postsynaptic potential (EPSP) leading to muscle contraction. Acethylcholine has to be rapidly removed from the synaptic cleft to allow for multiple signals to arrive at the muscle, as well as for repeated contractions in sustained muscle activity. Its removal is accomplished in part by the action of acetylcholinesterase that degrades the neurotransmitter. Galen (129-200), the father of experimental physiology, was the first to propose a realistic connection between muscle and nerve, Andreas Versalius (1514-1564) the first to show the functional relationship between the two, and Charles Bell (1774-1842) in 1811 that each muscle is supplied by two nerves, one motor (the ventral horn), the other sensory (the dorsal horn). Following the discovery of neuromuscular junction receptors by John Newport Langley (1852-1925), the first to identify acethycoline as the neuromuscular junction transmitter was Henry Hallett Dale (1875-1968) in 1914. The neuromuscular junction itself had been initially identified by means of light microscopy in the 1860s.
See Acetylcholine (AcH), Acetylcholinesterase (AcHE), Action potential, Axon retraction (or pruning), Botulinous (or botulinum, Boutons, Dorsal horn, Motoneuron, Motor end plate, Muscle fiber, Neurotransmiitters, Synapse, Synaptic cleft, Ventral horn