After detachment, what energizes the myosin head for the next cycle?

After detachment, what energizes the myosin head for the next cycle?

• A. The myosin head uses ATP energy to re-cock for the next cycle
• B. Calcium is pumped back into the sarcoplasmic reticulum
• C. ADP release deactivates the head
• D. Sodium influx triggers tightening

Answer: (A)

The energy comes from ATP hydrolysis. After detachment, the myosin head binds ATP and then hydrolyzes it to ADP and inorganic phosphate, which re-cocks the head into a high-energy, primed conformation. This energized state allows the head to form a new cross-bridge with actin, enabling the next contraction cycle once Pi is released and the power stroke occurs.

The energy comes from ATP hydrolysis. After detachment, the myosin head binds ATP and then hydrolyzes it to ADP and inorganic phosphate, which re-cocks the head into a high-energy, primed conformation. This energized state allows the head to form a new cross-bridge with actin, enabling the next contraction cycle once Pi is released and the power stroke occurs.