Resting state
Motor nerve action potential arrives at motor end plate
Acetylcholine released, sarcolemma and membranes depolarized (Na+ flux into fiber)
Action potential transmitted via T-tubules to SR
Ca++ released from SR terminal cisternae into sarcoplasm
Ca++ bound by troponin
Myosin ATPase activated and ATP hydrolyzed
Tropomyosin shift from actin binding site
Actin-myosin crossbridge formation
Repeated formation & breaking of crossbridges resulting in sliding of filaments and sarcomere shortening
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
(1) The nervous events that take place in contraction.
(2) The role of calcium in turning the muscle "on."
(3) The factors related to the actual contraction process.
(4) The events that take place to cause relaxation to occur.
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