Final answer:
In muscle contraction, the Z-line shifts towards the center of the sarcomere following the sliding filament model, facilitated by the action of myosin pulling actin filaments and powered by ATP hydrolysis.
Step-by-step explanation:
In muscle contraction, when actin filaments pull on both sides of the Z-line, the Z-line should shift towards the center of the sarcomere. This occurs as part of the sliding filament model of contraction. During this process, myosin heads bind to actin and pull it towards the center, powered by the hydrolysis of ATP. As a result, the Z-lines move closer together, shortening the sarcomere and causing muscle contraction.The H zone and the I band shorten during this contraction, but the A band remains the same length. The Z-lines are drawn towards the thick filaments and the sarcomere's zone of overlap increases as the actin filaments slide inward.
It is this movement that facilitates the muscle to contract and generate force.According to the sliding filament model of muscle contraction, when actin filaments pull on both sides of the Z-line, the Z-line shifts towards the center of the sarcomere. This is because the thin filaments are pulled by the thick filaments towards the center, causing the Z-lines to move closer together and shortening the sarcomere. As the actin is pulled towards the M line, the sarcomere shortens and the muscle contracts.