During the cross bridge cycle, what occurs after ADP is released from the myosin head?

The correct answer is that myosin slides the thin filament towards the sarcomere center after ADP is released from the myosin head. This step is crucial in the cross bridge cycle, where the release of ADP signifies that the power stroke has already occurred. When ADP is released, the myosin head is in a low-energy state and has already performed the work of pulling the actin filament towards the center of the sarcomere, which results in muscle contraction. This sliding motion occurs as the myosin head is firmly attached to actin, which leads to the contraction of the muscle fiber.

Understanding this step is key to comprehending muscle contraction, as the actin and myosin interaction is the fundamental mechanism by which muscles generate force. The release of ADP allows this sliding process to happen efficiently, enabling the muscle fibers to shorten and produce movement.