Question

During a muscle fiber contraction, which of the following decreases in size?

Check All That Apply.

a. A band.

b. Entire sarcomere.

c. H zone.

d. l band.

Answer 1

During muscle fiber contraction, the H zone and I band decrease in size, while the A band remains the same length. The entire sarcomere shortens due to the sliding filament model of muscle contraction.

Step-by-step explanation:

During a muscle fiber contraction, certain regions within the muscle fiber's sarcomere decrease in size. Specifically:

• The H zone, which contains only thick filaments, decreases in size during contraction.
• The I band, which contains only thin filaments, also decreases in size.
• The A band remains the same length; it does not shorten during muscle contraction.
• The entire sarcomere shortens, reducing the distance between Z lines, which are the boundaries of each sarcomere.

This process is explained by the Sliding Filament Model of Skeletal Muscle Contraction. According to this model, during contraction, the Z lines move closer together, the zone of overlap where thin and thick filaments occupy the same area increases, and the I band becomes smaller.