During a muscle contraction, which myofilament is pulled along?

During a muscle contraction, the actin myofilaments are pulled along by the myosin myofilaments through a process known as the sliding filament theory. In this mechanism, the myosin heads attach to binding sites on the actin filaments and pull them toward the center of the sarcomere, resulting in muscle shortening and contraction.

Actin is a key player in the contraction process, as it provides the structural framework on which myosin can exert force. The interaction between actin and myosin is regulated by proteins such as tropomyosin and troponin, which control the availability of binding sites on actin. While troponin plays a critical role in the regulation of muscle contractions by responding to calcium levels, it does not get pulled along itself. Titin, on the other hand, is a giant protein that helps maintain the structure of the sarcomere but does not participate directly in the contraction process. Therefore, the myofilament that is actively pulled along during contraction is actin.