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)?
A) acetylcholine (ACh) release
B) action potential propagation down the T tubules
C) conformational change in troponin
D) depolarization of the muscle cell
E) release of Ca2+ from the sarcoplasmic reticulum

Question

Quizplus · Accepted Answer

The conformational change in troponin occurs last in this sequence. After the action potential arrives at the NMJ, ACh is released, leading to depolarization of the muscle cell. This depolarization propagates down the T tubules, triggering the release of Ca2+ from the sarcoplasmic reticulum. The increase in Ca2+ concentration then leads to a conformational change in troponin, which is the final step in initiating muscle contraction.

When an Action Potential from a Motor Neuron Arrives at the Neuromuscular