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An action potential arrives at the presynaptic terminal causing voltage-gated
calcium ion channels to open, increasing the calcium ion permeability of the
presynaptic terminal cell membrane.
Calcium ions (Ca) enter the presynaptic terminal and cause vesicles to release
their neurotransmitter, acetylcholine (ACh), from the synaptic vesicles into the
presynaptic cleft.
Diffusion of acetylcholine across the synaptic cleft and binding of acetylcholine to
acetylcholine receptors on the postsynaptic muscle fiber membrane causes an
increase in the permeability of ligand-gated sodium ion channels.
The movement of sodium ions (Na) into the muscle cell results in depolarization
of the postsynaptic membrane. Once threshold has been reached, a postsynaptic
action potential is generated and is propagated over the muscle cell membrane.
Acetylcholine is rapidly broken down to acetic acid and choline in the synaptic
cleft by the enzyme acetylcholinestera
