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Muscles April 14

Muscles April 14 - Muscles April 14 Skeletal muscle...

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Muscles April 14 Skeletal muscle structure -muscle is a group of cells bound together by CT -skeletal muscle fibers may increase in size over lifetime, but do not grow new muscles -muscle fiber is a muscle fiber How muscles move bones -flexation vs. extension (one works as the other’s antagonist, e.g. biceps and triceps) -muscle connected to move bones Sliding filament theory -muscles are composed of a series of smaller and smaller units -single muscle is composed of muscle fibers (cells) -muscle fibers are single cells; multi-nucleated -muscle fiber (muscle cell) composed of myofibrils -myofibril composed of thick and thin filaments -thick filaments- myosin -thin filaments- actin Muscle fibers Myofibrils Thick filaments Myosin protein strand Thin filaments 2 actin strands Regulatory proteins coiled together -Functional unit is sacrascome- Sliding filament theory 1. actin: 2 coiled strands 2. myosin with golf-ball heat 3. tropomyosin- winds around actin 4. troponin- inhibits interaction; binds with Ca 2+ ; binds with tropomyosin Thick and thin filament arrangement in scarsome Shortening of scaromere causes muscle contraction Thick and thin filaments repeatedly bind to each other and slide past one another causing the scaramere to shorten 1. Myosin has hundreds of heads protruding from protein. These are binding sites for the thin filament protein actin. When muscle is in the relaxed state, myosin is bound to ATP, high energy state 2. Myosin hydrolyzes ATP ADP + P i
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