How are signals transmitted across a neuromuscular junction?
Calcium ions enter the presynaptic terminal via voltage gated calcium channels, once the presynaptic terminal is depolarised by an action potential.Calcium ions stimulate vesicles to fuse with the presynaptic membrane, and release the neurotransmitter acetylcholine by exocytosis.Acetylcholine diffuses across the synaptic cleft, and binds to ligand gated sodium channels on the sarcolemmaBinding of acetylcholine allows sodium ions to enter the muscle cell t-tubule system and depolarise this cell.Action potential is initiated and propagates along the t-tubule system.
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