A neuromuscular junction is the specialized synapse through which a somatic motor neuron excites a skeletal muscle fibre. Arrival of an action potential at the nerve terminal opens voltage-gated calcium channels; calcium entry triggers release of acetylcholine. Binding of acetylcholine to receptors on the muscle's motor end plate produces a local depolarization that normally triggers a muscle action potential.[ref]
Anatomy and Physiology 2e by J. Gordon Betts and others. Section 10.3, Excitation-Contraction Coupling
The electrical signal then initiates release of stored calcium within the muscle fibre, enabling contraction. Synaptic release and contraction are separate steps: the acetylcholine does not itself pull the contractile filaments. Breakdown of acetylcholine by acetylcholinesterase helps terminate the synaptic signal.[ref]
Anatomy and Physiology 2e by J. Gordon Betts and others. Section 10.3, The Neuromuscular Junction and Sliding Filament Model
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