Final answer:
During muscle contraction, the sarcomere and I band shorten while the A band's length remains unchanged but moves closer, leading to muscle fiber contraction and increased muscle tension.
Step-by-step explanation:
When a skeletal muscle generates enough force during contraction to shorten, the direct answer is D) the sarcomere and the I band will shorten. The A band remains the same length but moves closer together as the sarcomere shortens.
During contraction, muscle fibers utilize ATP to power the movement of myosin heads binding to actin, resulting in the sliding of thin filaments towards the center of the sarcomere. This action decreases the distance between the Z lines, causing the I bands to get smaller and the H zone to nearly disappear.
The A band, which comprises thick filaments, maintains its width even when the muscle is fully contracted. The overall shortening of each sarcomere leads to the contraction of the entire muscle fiber, increasing the total muscle tension.
During muscle contraction, the sarcomere, which is the fundamental unit of muscle contraction, shortens. The A band, which contains the thick filaments, does not change in length, but different A bands move closer together. The I band, which contains the thin filaments, also shortens. Overall, the shortening of these components results in muscle contraction and the generation of force.