phys muscle notes

phys muscle notes - Skeletal Muscle -striated -major...

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Skeletal Muscle -striated -major component of body mass -allows for interaction with the external environment -not all attached to skeleton -under control of somatic nervous system (CNS) -can only contract (shorten) -exist in pairs -fatigue tolerance varies -produce body heat -attached to bone by tendons 1. insertion-movable attachment 2. origin- less movable attachment -contracting a muscle causes tension 1.flexors-decrease angle of joint 2. extensors- increase angle of joint -agonist = prime mover of any skeletal movement -antagonistic muscles = muscles that act on the same joint to produce opposite actions Structure of Muscle
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Muscle Fiber: muscle fiber--> myofibrils-->sarcomere-->myofilaments-->thick and thin filaments -thick filaments= myosin -thin filaments= actin, troponin, tropomyosin Myofibril: A band = dark, mostly thick filaments (myosin) H band = light area at center of A band = where actin and myosin DO NOT overlap I band = light, mostly thin filaments (actin) Z line = center of I band = where actin attach
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Contractile unit: Sarcomere -muscle contracts because the thick and thin filaments slide past one another contraction: actin and myosin must interact Sites of Interaction: Cross Bridges -heads of myosin interact with actin -sliding of filaments is produced by action of cross bridges -each myosin head contains an ATP binding site which functions as an ATPase 1. ATP binds to myosin head 2. ATP is hydrolyzed to ADP 3. Binds to actin 4. Myosin undergoes conformational change (power stroke) which exerts force on actin and slides filaments 5. ADP released 6. Myosin detaches 7. New ATP formed
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Contraction Requires an Increase in Free Ca -when Ca is low, muscle is relaxed because actin and myosin are unable to interact
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phys muscle notes - Skeletal Muscle -striated -major...

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