The displacement of tropomyosin exposes the active sites of actin, allowing cross bridges to form. Troponin controls the position of tropomyosin on the thin filament, enabling myosin heads to bind to the active sites on actin
After Ca2+ is released from the sarcoplasmic reticulum, it binds with Troponin C, alters its shape and removes the tropomyosin from the binding site. Then, the myosin head binds to the exposed active sites of actin to form cross-bridges.
