Muscles - November 5th 2007 Reading Chapter 9 3 types of...

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November 5 th 2007 Reading: Chapter 9 3 types of muscle: Skeletal and cardiac are striated and smooth (it contains myosin but not arranged as in the others) Skeletal muscle innervated by somatic motor system in the dorsal horn Cardiac and smooth- autonomic nervous system Skeletal muscle- 40% of body mass, know the structure (fascicles, myofibrils) Excitable peripheral membrane around muscle fiber, t-tubule propagates an action potential, expanded web of calcium storage known as sarcoplasm (sarcoplasmic reticulum) Triad- t-tubule surrounded by buds of SR (aka terminal cisternae) G-actin polymerizes to form an alpha helix, known as the actin filaments. Tropomyosin covers actin binding sites Troponin is a 3-subunit protein that binds calcium Myosin- Thick filaments, contains a heavy chain, <light chain, and two binding sites one for ATP one for actin (2 on each crossbridge)> aka crossbridge Titin-elastic anchor for myosin, you can get muscle shortening with no tension developed because it takes a certain amount of time to adjust the elastic component Nebulin helps align actin, non elastic component which is a structural component. M-line-region of protein connections between tail regions of myosin H-zone region in center where there is no overlap, shortens, includes the m-line I-band- region where there is no overlap between thick and thin filaments, if you shine light through it it lets it through (isotropic band), shortens, includes the z-disk A-band (anisotropic)-diffracts light, constant, myosin end to end length Molecular mechanisms of skeletal muscle contraction Crossbridge holds ADP and inorganic phosphate, intracellular calcium increases, binds troponin, moves tropomyosin, binding of myosin and actin Angular movement means release of ADP and inorganic phosphate, this means rigor state, actin and myosin are binded (until ATP is introduced) in an angular relationship. When ATP binds the myosin head causes release of actin, hydrolysis of ATP brings about the original relaxed state. ATP is never a limiting factor in real life for muscle contraction. Excitation-contraction coupling:
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This note was uploaded on 05/18/2008 for the course BIO 328 taught by Professor Cabot during the Fall '07 term at SUNY Stony Brook.

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Muscles - November 5th 2007 Reading Chapter 9 3 types of...

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