Question

question 6
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which of the following events is the cause of sarcolemma depolarization?
acetylcholine (ach) inactivation and degradation
iqitiation of excitation - contraction coupling
rapid propagation of an electrochemical signal along the sarcolemma
sodium moving into the cell through acetylcholine receptors (achr)

Explanation:

When acetylcholine (ACh) binds to acetylcholine receptors (AChR) on the sarcolemma, sodium ions ($Na^+$) move into the cell. This influx of positively - charged sodium ions changes the membrane potential, leading to depolarization of the sarcolemma. Acetylcholine inactivation and degradation would stop the signal rather than cause depolarization. The initiation of excitation - contraction coupling is a later event in muscle contraction that depends on depolarization. The rapid propagation of an electrochemical signal along the sarcolemma is the result of depolarization, not its cause.

Answer:

Sodium moving into the cell through acetylcholine receptors (AChR)