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36 Cards in this Set
- Front
- Back
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3 types of muscle
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Skeletal
Cardiac Smooth |
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Basic unit of skeletal muscle
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Fiber
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Basic unit of cardiac and smooth muscle
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Cell
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General characteristics of skeletal muscle
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MULTINUCLEATED SYNCITIUM
Formed by fusion of small myoblasts Diameter 100-100 microns Length can be from few millimeters to meter Cell membrane- sarcolemma (nuclei are under) Cross striation |
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3 types of connective tissue in skeletal muscle
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Endomysium
Perimysium Epimysium |
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Endomysium
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Thin layer of reticular fibers surrounding individual muscle fibers
Contains capillaries and smallest nerve fibers -almost undetectable |
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Perimysium
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Thicker connective tissue layer surrounding bundles of fibers (fascicle)
Contains large blood vessels and nerves |
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Epimysium
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Sheath of dense connective tissue surrounding collection of fascicles
Carries major vascular and nerve supply |
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2 types of muscle fibers in skeletal muscle
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Red and white
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Red fibers
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-Small
-A lot of myoglobin and mitochondria -Great resistance to fatigue -Less muscle tension -Slow twitch motor units -Found in leg and breast of migrating birds |
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White fibers
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-Large
-Little myoglobin and mitochondria -Fatigue rapidly -Large peak muscle tension -Fast twitch motor unit -Precise control -Extraocular muscles, finger muscles |
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Intermediate fibers
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Intermediate size and myoglobin levels
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Muscle fascicle
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Bundle of fibers
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Myofibril
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Structural and functional unit of muscle
Syncitium |
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Thick myofilament
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-Myosin II composed of two heavy polypeptide chains and four light chains
-Globular myosin head has binding sites for ATP and actin |
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F actin
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double helix, composed of G actin subunits
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Tropomyosin
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two double helix polypeptide chains - masks myosin binding site of actin in resting muscle
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Troponin C binds..
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Ca
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Troponin T binds..
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to tropomyosin
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Troponin I binds..
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to actin, inhibiting actin myosin interaction
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A band is mostly
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dark band, mostly thick myosin filaments in relaxed muscle
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I band
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isotropic, light band (mostly thin filaments of actin)
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Z line
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darker line at the middle of I line
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Sarcomere
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Portion of myofibril between two Z lines, basic contractile unit of striated muscle
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M line
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Middle of sarcomere
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In contraction I line
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decreases
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Alpha actinin, desmin and nebulin
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anchor thin filaments in Z line
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Titin
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anchors thick filaments in Z line
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Tropomodulin
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maintains length of actn filament
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Myomesin and C protein
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hold thick filaments aligned at M line
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Dystrophin
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anchors actin to laminin
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Absense of dystrophin results in
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Duschenne dystrophy
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Terminal cisterna stores
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Ca
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T tubules
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Penetrate into muscle fibers and regulate Ca channels
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Triad
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T tubules and adjacent terminal cisternae at border of A and I bands
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What triggers Ca release from terminal cisternae
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Depolarization of T tubule
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