Neuromusclular Junciton
...ntial arrives at axon terminal. Acetylcholine is released. Depolarization of motor end plate. Action potential propagates along sarcolemma and down T tubules. Contraction of sarcomeres. When action potential arrives at the axon terminal, the voltage charge of the membrane opens voltage regulated calcium channels allowing calcium ions to enter the axon terminal. The calcium ions cause several synaptic vesicles to fuse with the membrane of the axon terminal. The neurotransmitter acetylcholine is liberated by exocytosis into the synaptic cleft. Additionally, calcium ions are pumped out of the axon terminal. Acetylcholine binds to the receptor sites of chemically regulated ion channels in the motor end plate. This causes the channels to open up, permitting and influx of sodium ions and a small efflux of potassium ions. This ion exchange causes a local depolarization at the motor end plate. After a...