When acetylcholine is released into the neuromuscular junction, a) action potent

Question

When acetylcholine is released into the neuromuscular junction,

a) action potentials are triggered, which lead to activation of the contraction cycle. b) the muscle membrane depolarizes, creating an end-plate potential (EPP). c) it binds to receptors that allow Na+ and K+ ions to cross the sarcolemma. d) it binds to receptors that allow Na+ and K+ ions to cross the sarcolemma and the muscle membrane depolarizes, creating an end-plate potential (EPP). e) it binds to receptors that allow Na+ and K+ ions to cross the sarcolemma, the muscle membrane depolarizes, creating an end-plate potential (EPP), and action potentials are triggered, which lead to activation of the contraction cycle.

Explanation / Answer

Answer. E. it binds to receptors that allow Na+ and K+ ions to cross the sarcolemma, the muscle membrane depolarizes, creating an end-plate potential (EPP), and action potentials are triggered, which lead to activation of the contraction cycle.

When acetylcholine vesicles are released because of action potential, it diffuses across the synaptic cleft and binds to nicotinic acetylcholine receptors (nAChRs) on the cell membrane of the muscle fiber, also known as the sarcolemma. This binding causes the nicotinic receptor channels to open and let sodium ions to enter the muscle fibre resulting in depolarization of the sarcolemma. The small depolarization associated with the release of acetylcholine from one synaptic vesicle is called a miniature end-plate potential (MEPP) and its additive effect lead to a greater depolarization of the postsynaptic membrane and become end plate potentials (EPPs). When EPPs cause the membrane to reach threshold (-mV), the voltage gated ion channels in the postsynaptic membrane open causes in influx of sodium ions and a sharp spike in depolarization. It causes an action potential to occur and spread down the postsynaptic membrane leading to muscle contraction

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