Neuromuscular junction: rmp in muscle cells is -90mv, sequence of events in neuromuscular transmission, action potential in alpha-motor nerve, depolarization of alpha-motor nerve terminal, voltage-gated calcium channels open. 4: movement of calcium causes fusing of ach vesicles to membrane terminal, and releases ach in. Influx of calcium quantal amounts: diffusion of ach to muscle cell membrane endplate, attachment of ach to nicotinic ach receptors at endplate, opening of non-specific cation channels (ligand-gated channels) Preferential influx of sodium because rmp of muscle cell is at the equilibrium potential for potassium: preferential influx of sodium into muscle cell. 10. depolarization of muscle cell membrane at the endplate (endplate potential [epp]) no ap yet. 11. local currents open voltage-gated sodium & potassium channels on membrane adjacent to endplate production of ap. 12. ap propagates outward in all directions along muscle cell. 13. ach broken down to choline & acetate by acetylcholinesterase.