Sliding Filament Theory steps (in order):
1. Calcium ions are released by sarcoplasmic reticulum into the sarcoplasm.
2. The breakdown of ATP releases energy, releasing the head of the myosin.
3. Calcium ions bind to troponin, exposing the binding site on the actin filament.
4. The myosin head attaches to the exposed binding site on the actin filament, forming a
cross-bridge.
5. The flexing of the cross-bridge pulls the actin filament toward the center of the
sarcomere.
6. An ATP molecule in the reattaches to the ATP binding site on the myosin head.
7. The myosin head is released from the actin filament’s binding site and the binding site is
covered up again.
8. With the ATP molecule in place on the myosin head and calcium ions present, the cycle
can continue.