Actin Heads Filaments Binding Binds Contraction Sites Myosin

actin filaments have binding sites for myosin heads (actin-myosin binding sites), normally blocked by tropomyosin (so muscle relaxed), when signal stimulates muscles to contract, mysoin heads binds to actin forming mysoin-actin cross-bridges, the heads flex (change angle) which moves actin filaments along, then heads detach and unflex (using ATP) and binds further along actin filament, and process continues