Calcium ions are released from the sarcoplasmic reticulum. They attach to troponin which causes tropomyosin to change shape, rotate, and expose binding sites on the actin filament.

The myosin head attaches to the actin filament, an inorganic phosphate is released, and the bond to actin is strengthened.

ADP is released from the myosin head which causes the myosin head to pivot and pull the actin filament towards the center of the sarcomere.

Another ATP molecule attaches to the myosin head causing it to detach from the actin filament.

ATP is hydrolyzed into ADP and an inorganic phosphate, and the energy released moves the myosin head back into the cocked position.

Calcium ions leave troponin which causes tropomyosin to rotate back and cover the binding sites on the actin filament and the muscle is done contracting. The calcium ions are actively transported back into the sarcoplasmic reticulum.

Calcium ions are released from the sarcoplasmic reticulum. They attach to troponin which causes tropomyosin to change shape, rotate, and expose binding sites on the actin filament. The myosin head attaches to the actin filament, an inorganic phosphate is released, and the bond to actin is strengthened. ADP is released from the myosin head which causes the myosin head to pivot and pull the actin filament towards the center of the sarcomere. Another ATP molecule attaches to the myosin head causing it to detach from the actin filament. ATP is hydrolyzed into ADP and an inorganic phosphate, and the energy released moves the myosin head back into the cocked position. calcium ions leave troponin which causes tropomyosin to rotate back and cover the binding sites on the actin filament and the muscle is done contracting. The calcium ions are actively transported back into the sarcoplasmic reticulum.