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Unformatted text preview: Skeletal muscle fibers Sarcolemma (cell membrane) Sarcoplasm (muscle cell cytoplasm) Sarcoplasmic reticulum (modified ER) T-tubules and myofibrils aid in contraction Sarcomeres regular arrangement of myofibrils Myofibrils Thick and thin filaments Organized regularly Muscle Fiber Thin filaments F-actin Nebulin Tropomyosin Covers active sites on G-actin Troponin Binds to G-actin and holds tropomyosin in place Thick filaments Bundles of myosin fibers around titan core Myosin molecules have elongate tail, globular head Heads form cross-bridges during contraction Interactions between G-actin and myosin prevented by tropomyosin during rest...
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