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. #Pathophysiology #Cardiology #Myocyte #Contractile #Cycle #Contraction
