B. Â
Relaxation Phase
Cholinesterase released and acetylcholine breakdown
Sarcolemma & T-tubules repolarized
SR Ca++ pump activated & Ca++ returned to SR terminal cisternae
Actin-myosin crossbridge formation terminated
Return of tropomyosin to actin binding site
Mg++ complex formed with ATP
Passive sliding of filaments
Sarcomeres return to resting state