Which of the statements about muscle contraction are correct? During muscle contraction, the sarcomere becomes shorter. During muscle contraction, the band becomes shorter. During muscle contraction, the H zone becomes shorter. During muscle contraction, the distance between the Z disk and the M disk becomes shorter. All of the answers above are correct.
The Correct Answer and Explanation is:
The correct answer is: All of the answers above are correct.
Explanation:
Muscle contraction occurs through a process called the sliding filament theory, where the thick and thin filaments (myosin and actin) within the sarcomere interact to shorten the muscle fiber. Here’s how the statements fit into this process:
- During muscle contraction, the sarcomere becomes shorter:
The sarcomere is the functional unit of muscle contraction. It is the region between two Z discs. As actin (thin filament) and myosin (thick filament) slide over each other, the sarcomere shortens, leading to muscle contraction. - During muscle contraction, the band becomes shorter:
This refers to the I band, which is the region of the sarcomere containing only actin filaments. During contraction, the actin filaments slide past the myosin filaments, reducing the length of the I band. - During muscle contraction, the H zone becomes shorter:
The H zone is the part of the sarcomere where only myosin filaments are present. As actin filaments slide toward the M line, the H zone shrinks, or may even disappear, because the actin filaments overlap more with the myosin filaments during contraction. - During muscle contraction, the distance between the Z disk and the M disk becomes shorter:
The Z disk marks the boundary of the sarcomere, while the M disk is at the center of the sarcomere, where myosin filaments are anchored. As the actin filaments slide inward, the distance between these two disks decreases, contributing to the shortening of the muscle.
All these changes are driven by the interaction between actin and myosin filaments in response to signals from the nervous system, leading to muscle contraction and overall shortening of the muscle.
