Which of the following is the correct sequence that occurs during the excitation and contraction of a muscle cell?
1) Tropomyosin shifts and unblocks the cross-bridge binding sites.
2) Calcium is released and binds to the troponin complex.
3) Transverse tubules depolarize the sarcoplasmic reticulum.
4) The thin filaments are ratcheted across the thick filaments by the heads of the myosin molecules using energy from ATP.
5) An action potential in a motor neuron causes the axon to release acetylcholine, which depolarizes the muscle cell membrane.
A)1, 2, 3, 4, 5
B)2, 1, 3, 5, 4
C)2, 3, 4, 1, 5
D)5, 3, 1, 2, 4
E)5, 3, 2, 1, 4

Question

Quizplus · Accepted Answer

The correct sequence is: an action potential causes acetylcholine release (5), which depolarizes the muscle cell membrane and transverse tubules (3), leading to calcium release that binds to troponin (2), causing tropomyosin to shift and unblock binding sites (1), allowing myosin to ratchet thin filaments using ATP (4).

Which of the Following Is the Correct Sequence That Occurs