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Titin Type of structural protein that stabilizes the position of myosin Regulatory Category of proteins that switches the contraction process on and off action potentials What causes the release of calcium from the SR into the muscle cell Dystrophin Type of protein that links the thin filaments to the sarcolemma Contractile Category of proteins that generates the force during contraction Length The forcefulness of a muscle contraction depends on the ____ of the sarcomere Actin Type of protein that provides a site where a myosin head can attach Actin/ Thin During the sliding filament mechanism which filament is pulled toward the center Myosin Which type of contractile protein converts ATP to energy of motion Structural Category of proteins that aligns the thick and thin filaments properly calcium Which ion is most important in starting the contraction of the muscle ATP Hydrolysis/ Formation of cross Bridges/ Power Stroke/ Detachment of myosin from Actin List the four steps of the contraction cycle (In order) Z discs seperate one sarcomere from the next A band middle part of sarcomere where thick and thin filaments overlap one another I band lighter part of a sarcomere, contains thin but no thick filaments H zone center of each A band which contains thick but not thin filaments M line supporting proteins that hold the thick filaments together in the H zone muscle proteins what are myofibrils built from troponin, tropomyosin two types of regulatory proteins myosin, actin two types of contractile proteins titin, dystrophin two types of structural proteins sliding filament mechanism myosin heads attach to and walk along thin filaments at both ends of a sarcomere shortens what happens to the sarcomere and muscle after the sliding filament mechanism? contraction cycle the onset of contraction begins with the SR releasing calcium ions into the muscle cell, where they bind to actin opening the myosin binding sites ATP hydrolysis step where hydrolosis of ATP reorients and energizes the myosin head formation of cross-bridges step where myosin head attaches to the myosin-binding site on actin power stroke step when the crossbridge rotates, sliding the filaments detachment of myosin from actin step when as the next ATP binds to the myosin head, the hyosin head detaches from actin ATP, Ca++ the contraction cycle repeats as long as what two things are available? Ca++ pumps the muscle cell membrane contains what that return Ca++ back to the SR quickly? relaxes what happens to the muscle as the Ca++ level in the cell drops?