Which of the following is the correct sequence that describes the excitation and contraction of a skeletal muscle fi
1) Tropomyosin shifts and unblocks the cross- bridge binding sites.
2) Calcium is released and binds to the troponin complex.
3) The sarcoplasmic reticulum is depolarized when a wave of depolarization moves from the neuromuscu junction into the cell's interior by way of the transverse tubules.
4) The thin filaments are ratcheted across the thick filaments by the heads of the myosin molecules using e from ATP.
5) An action potential in a motor neuron causes the axon to release acetylcholine, which depolarizes the muscle cell membrane at the neuromuscular junction.

Question

Quizplus · Accepted Answer

The correct sequence for the excitation and contraction of a skeletal muscle fiber starts with the action potential in a motor neuron causing the release of acetylcholine at the neuromuscular junction (5), followed by depolarization of the sarcoplasmic reticulum via transverse tubules (3), leading to the release of calcium which binds to the troponin complex (2). This causes tropomyosin to shift and unblock the cross-bridge binding sites (1), allowing the myosin heads to bind to the thin filaments and use ATP to ratchet across them, causing muscle contraction (4).

Which of the Following Is the Correct Sequence That Describes