Final answer:
The dissociation of the actinomyosin complex in the contractile cycle is most immediately caused by the release of ADP and inorganic phosphate (Pi) from the myosin head.
Step-by-step explanation:
In the contractile cycle, the dissociation of the actinomyosin complex results most immediately from the release of ADP and inorganic phosphate (Pi) from the myosin head. The dissociation of the actinomyosin complex in the contractile cycle is most immediately caused by the release of ADP and inorganic phosphate (Pi) from the myosin head.
This release of ADP and Pi causes a conformational change in the myosin head, leading to its detachment from the actin filament. The myosin head remains in a high-energy conformation until it binds another ATP and undergoes another conformational change to return to its original position.