Arrange the following steps of muscle fiber contraction in the correct sequence. 1. The muscle impulse reaches the sarcoplasmic reticulum and calcium is released.
2) Thin filaments are pulled over the thick filaments.
3) Calcium floods the sarcoplasm and binds to troponin molecules leaving active sites.
4) The impulse arrives at the synapse and travels through the transverse tubules.
5) The muscle fiber shortens and contracts.
6) Myosin heads bind to exposed active sites on actin, forming cross-bridges.
A)4, 1, 3, 5, 6, 2
B)4, 1, 3, 2, 6, 5
C)4, 1, 3, 6, 2, 5
D)4, 3, 6, 2, 5, 1

Question

Arrange the following steps of muscle fiber contraction in the correct sequence. 1. The muscle impulse reaches the sarcoplasmic reticulum and calcium is released.
2) Thin filaments are pulled over the thick filaments.
3) Calcium floods the sarcoplasm and binds to troponin molecules leaving active sites.
4) The impulse arrives at the synapse and travels through the transverse tubules.
5) The muscle fiber shortens and contracts.
6) Myosin heads bind to exposed active sites on actin, forming cross-bridges.
A)4, 1, 3, 5, 6, 2
B)4, 1, 3, 2, 6, 5
C)4, 1, 3, 6, 2, 5
D)4, 3, 6, 2, 5, 1

Quizplus · Accepted Answer

The sequence of muscle fiber contraction starts with the arrival of the impulse at the synapse, which travels through the transverse tubules (4). This triggers the release of calcium from the sarcoplasmic reticulum (1) which floods the sarcoplasm and binds to troponin molecules, leaving active sites (3). The myosin heads then bind to these exposed active sites on actin, forming cross-bridges (6). The thin filaments are then pulled over the thick filaments (2), resulting in muscle fiber shortening and contraction (5). Therefore, the correct sequence is 4, 1, 3, 6, 2, and 5. 
Option C is the correct choice as it represents the right sequence.

Arrange the Following Steps of Muscle Fiber Contraction in the Correct