What produces power strokes according to the sliding filament theory?

The sliding filament theory explains how muscles contract at the molecular level, particularly through the interactions between the proteins actin and myosin. Myosin is a motor protein that plays a crucial role in muscle contraction. According to the theory, when a muscle is stimulated to contract, myosin heads bind to sites on the actin filaments, forming cross-bridges.

Once these cross-bridges are formed, the myosin heads pivot and pull the actin filaments toward the center of the sarcomere, which results in the "power stroke." This action is powered by the hydrolysis of ATP (adenosine triphosphate), which provides the energy necessary for myosin heads to perform this movement. Essentially, myosin is responsible for generating the force that leads to muscle contraction and thus produces the power strokes that cause the sliding action of actin filaments, contributing to overall muscle shortening and movement.

Other components like actin, tropomyosin, and calcium ions have important roles in the process but do not directly produce the power strokes. Actin serves as the filament that myosin interacts with, while tropomyosin regulates these interactions and calcium ions play a role in exposing binding sites on actin for myosin, but