Cardiac Myocyte Contractile cycle
 - Ca2+ binds to TnC → TnI is inhibited → conformational change in tropomyosin that exposes active site between actin and myosin.
 - Myosin heads interact with active sites on actin filaments and “flex,” like oars on a boat, to “row” myosin along actin in an ATP-dependent reaction:
 - ADP is released from the myosin head, which then binds a new ATP, releasing the actin filament.
 - The cycle can then repeat itself, allowing myosin to travel further along the actin molecules and progressively shorten the muscle fibers, as long as (i) the cytosolic Ca2+ concentration remains sufficiently high to inhibit the action of TnI and (ii) there is enough ATP to drive crossbridge formation.


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