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Events of Muscle Relaxation. The enzyme, acetylcholinesterase (AChE), in the neuromuscular junction, breaks down remaining acetylcholine in the synaptic cleft.
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Events of Muscle Relaxation • The enzyme, acetylcholinesterase (AChE), in the neuromuscular junction, breaks down remaining acetylcholine in the synaptic cleft. • Sodium ions are not released into the motor end plate (muscle fiber) stopping the generation of a muscle action potential which would travel through the T tubules. • Calcium ion channels close on the SR and Ca+2 is reabsorbed (actively pumped) from the sarcoplasm into the sarcoplasmic reticulum. • Calcium ions cannot bind to troponin causing the tropomyosin complex to slide back over myosin binding sites on actin. • Cross-bridges separate and the muscle fiber resumes its resting state, or relaxation