Cross bridge formation Energized myosin head attaches to an actin myofilament

Cross bridge formation energized myosin head attaches

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Cross bridge formation. Energized myosin head attaches to an actin myofilament, forming a cross bridge. Cocking of the myosin head. As ATP is hydrolyzed to ADP and Pi, the myosin head returns to its prestroke high-energy, or “cocked,” position. * Cross bridge detachment. After ATP attaches to myosin, the link between myosin and actin weakens, and the myosin head detaches (the cross bridge “breaks”). The power (working) stroke. ADP and P i are released and the myosin head pivots and bends, changing to its bent low-energy state. As a result it pulls the actin filament toward the M line. 1 2 3 4
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Sliding Filament Model of Contraction Generation of force does not necessarily cause shortening of fiber shortening occurs when tension generated by cross bridges on thin filaments exceeds forces opposing shortening
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Fully relaxed sarcomere of a muscle fiber Z H Z I I A
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Fully contracted sarcomere of a muscle fiber Z Z I I A
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Muscle Force-Length relationship
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Sarcoplasmic Reticulum (SR) and T tubules network of smooth endoplasmic reticulum surrounding each myofibril pairs of terminal cisterns form perpendicular cross channels functions: stores and releases Ca 2+ Sarcolemma Triad: • T tubule • Terminal cisterns of the SR (2) Tubules of the SR Myofibrils Mitochondria
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Part of a skeletal muscle fiber (cell) Myofibril Sarcolemma I band A band I band Z disc H zone Z disc M line Sarcolemma Triad: T tubule • Terminal cisterns of the SR (2) Tubules of the SR Myofibrils Mitochondria
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Rigor Mortis cross bridge detachment requires ATP 3–4 hours after death muscles begin to stiffen with weak rigidity at 12 hours post mortem Dying cells take in calcium cross bridge formation No ATP generated to break cross bridges
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Macroscopic-Anatomy of Striated Skeletal Muscle
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Microscopic-Anatomy of Striated Skeletal Muscle
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Sliding Filament Model of Muscle Contraction
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What should you be able to do now? contrast skeletal, cardiac, and smooth muscle list muscle properties and functions explain the anatomical organization of skeletal muscle relate the microscopic structure of skeletal muscle to its striation tell how the brain activates a muscle explain the sliding filament model of contraction
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  • Spring '14
  • BrettG.Szymik
  • Physiology, cross bridge, skeletal muscle fiber

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