Cellular component

The junction between the axon of a motor neuron and a muscle fiber. In response to the arrival of action potentials, the presynaptic button releases molecules of neurotransmitters into the synaptic cleft. These diffuse across the cleft and transmit the signal to the postsynaptic membrane of the muscle fiber, leading to a change in post-synaptic potential.

NMJ, motor endplate

In vertebrates, the term 'neuromuscular junction' is limited to synapses targeting skeletal muscle fibers - all of which are cholinergic and excitatory. Both inhibitory and excitatory neuromuscular junctions exist in invertebrates, utilizing a range of neurotransmitters including glutamate, GABA and 5-HT.