When an action potential from a motor neuron arrives at the neuromuscular juncti
ID: 303185 • Letter: W
Question
When an action potential from a motor neuron arrives at the neuromuscular junction (NMJ), a series of events occurs that leads to muscle contraction. Which of the following events will occur last (that is, after all of the others listed below)?
depolarization of the muscle cell
release of Ca2+ from the sarcoplasmic reticulum
acetylcholine (ACh) release
conformational change in troponin
depolarization of the muscle cell
release of Ca2+ from the sarcoplasmic reticulum
acetylcholine (ACh) release
conformational change in troponin
Explanation / Answer
The final step in muscle contraction is release of Ca2+ from the sarcoplasmic reticulum and immediately begin to resequester every calcium ions that have been released and when the Ca2+ ions are absent, we will observe a change in the configuration of troponin and tropomyosin which blocks action of the myosin molecule heads and contraction ceases.
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