Function of Neuromuscular Junction notes

action potential arrives at presynaptic terminal —> causes voltage gated calcium ions to open —> increasing calcium ion permeability of presynapatic cell membrane

calcium ions flow in —> cause vesicles to release ACh into presynaptic cleft

ACh diffuse across synaptic cleft and binding to ACh receptors on postsynaptic muscle fiber membrane

• causes permeability in ligand-gated sodium ion channels

movement of sodium ions into cell —> depolarization of postsynaptic membrane

once threshold reached, postsynaptic action potential is generated and propagated across muscle cell membrane

ACh rapidly broken down into acetic acid + choline in synaptic cleft by the enzyme acetylcholinesterase

• choline is reabsorbed by presynaptic terminal and combined with acetic acid to form more ACh, which enters the synaptic vesicles