c a ls e q u e s tr in triads tw o te r m in a l c is te r n a e o n e T tu b u

C a ls e q u e s tr in triads tw o te r m in a l c is

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c a ls e q u e s tr in triads tw o te r m in a l c is te r n a e o n e T - tu b u le Calcium ion concentrations related to muscle physiology Cytosol: 1 x 10 -7 mmol/liter ( 0.0000001 mmol/l) ECF: 2.0 mmol/liter SR : 1 x 10 -4 mmol/liter (0.0001 mmol/l) Sarcomere structure Basic functional unit of myofibrils 10,000 sarcomeres may exist end to end per fiber Extend from Z line to Z line A band length of thick filament I band between A bands
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5/21/19 4 Sarcomere structure in 3 dimensions Thick filament Contains 300 myosin molecules Myosin – Myosin tail – Myosin head F o r m s c r o s s b r id g e s w ith a c tin Energized by ATP Myosin ATPase Thin filament: 4 components F actin strand G actin molecules Active site for myosin Tropomyosin Cover active sites in resting fibers Troponin Binds Ca +2 Ca + 2 ion binding to troponin pulls on tropomyosin, exposing active site
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5/21/19 5 Sarcomere changes during contraction sliding filament theory myofilaments interact, the result: Shortening of the sarcomere Control of contraction Signal from nervous system causes contraction of muscle Starts at the neuromuscular junction Excitation-contraction coupling
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  • Spring '18
  • Mark Bolke

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