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muscle09 - Characteristics of Muscle Types Skeletal Muscle...

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Characteristics of Muscle Types Skeletal Muscle: Requires Action Potentials & Motor Neurons “twitch” contractions; striated Cardiac Muscle: Action potentials, but no motor neurons (“pacemaker” cells); “twitch” type contractions autonomic nervous system modulates Smooth Muscle: no motor neurons; pacemaker cells & autonomic nervous system; action potentials in some types; non-twitch slow contractions. Fig 9-1
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Fig 9-2 (Single muscle cell) Organization of Skeletal Muscle
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Electron micrographs of muscle show a repeat pattern of alternating dark (A) and light (I) bands Similar to Fig 9-3a Sarcomere: z-line to z-line = functional unit
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Summary Muscle cells (fibers) contain myofibrils Myofibrils show alternating light (I) and dark (A) bands I bands are bisected by “z-lines” I bands contain “thin filaments” = actin A bands contain thick filaments = myosin Z-line to Z-line = “sarcomere”
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Details of filaments in a single sarcomere Fig 9-3b A-band is composed of myosin “thick” filaments I-band composed of actin “thin” filaments plus regulatory proteins Thin filaments partially overlap thick filaments and amount of overlap changes with shortening
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