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Multiple Choice
In the context of the sliding filament theory, what is the H zone within a sarcomere?
A
The area that shortens during muscle contraction
B
The central part of the A band where only myosin filaments are present
C
The region where actin and myosin filaments overlap
D
The boundary between adjacent sarcomeres
Verified step by step guidance
1
Begin by understanding the structure of a sarcomere, which is the basic functional unit of muscle fibers. It is composed of repeating units between two Z lines.
Identify the A band within the sarcomere. The A band is the dark area that contains the entire length of the thick filaments, primarily composed of myosin.
Recognize the H zone as the central part of the A band. It is the region where only myosin filaments are present, without overlapping actin filaments.
During muscle contraction, the sliding filament theory explains that actin filaments slide over myosin filaments, leading to the shortening of the sarcomere.
Note that the H zone shortens during muscle contraction because the actin filaments move into this region, reducing the area where only myosin is present.