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. 6, 3, 1, 4, 2, 5
B. 2, 5, 3, 1, 4, 6
C. 4, 1, 3, 6, 2, 5
D. 3, 5, 2, 1, 6, 4

Answer 1

The correct sequence for muscle fiber contraction is: the impulse travels through transverse tubules, calcium is released from the sarcoplasmic reticulum, calcium binds to troponin on actin, myosin heads form cross-bridges with actin, thin filaments slide over thick filaments, and the muscle fiber contracts.Hence the correct answer is option C: 4, 1, 3, 6, 2, 5.

Step-by-step explanation:

To answer the question regarding the correct sequence of steps during muscle fiber contraction, you must understand the physiological processes behind muscle contraction. Here is the correct arrangement of the given steps:

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

This sequence follows the sliding filament model of muscle contraction, which involves the release of calcium ions from the sarcoplasmic reticulum, the exposure of binding sites on the actin filament, the formation of cross-bridges between actin and myosin, and the shortening of the muscle fiber as a result of the sliding of the thin filaments over the thick ones. This contraction process is powered by ATP.