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Skeletal Muscle

Skeletal Muscle

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Skeletal Muscle

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  1. Skeletal Muscle • State possible sources of fatigue • Distinguish the different muscle fiber types.

  2. Central Peripheral Afferent Feedback Psychological Motivation Neural Transmission Muscular Transmission • AP Propagation • AP Propagation Muscular contraction • cross-bridge interference Origins of Localized Muscle Fatigue SITES OF THE SOURCES OF FATIGUE

  3. ATP Origins of Localized Muscle Fatigue Depletion Theory of Fatigue: Fatigue results from the depletion of metabolites necessary for energy production Glucose Oxygen ADP or CP Reaction Enzymes

  4. Decreases membrane excitability • Decreases Ca++ affinity for Troponin • Inhibits Aerobic Metabolism • Decreases the release of Ca++ • Obstructs glycolysis Origins of Localized Muscle Fatigue Accumulation Theory of Fatigue: Lactic Acid and free H+ K+ NH3

  5. Skeletal Muscle Fiber Types • innervating nerve is primary determinant of fiber type during development • a motor unit is composed of homogenous fibers • all human muscles contain mixture of three general fiber types • slow twitch (ST, oxidative, red) • fast twitch (FTa, fast-oxidative, red) • fast twitch (FTb, glycolytic, white)

  6. Time Course of Contributions from Different Energy Sources fast twitch glycolytic (white) slow twitch oxidative (red) Oxidative

  7. Fiber Type Characteristics Performance characteristics affected by: • Ca2+-ATPase • myosin ATPase speed • aerobic capacity (mitochondria, myoglobin, blood supply, fatigue resistance) • anaerobic capacity (glycolytic enzymes)

  8. Muscle Movements‘Not all force results in movement.’ • Isotonic - (same force), muscle fibers create a force that moves a load. Muscle shortens or lengthens. • Isometric - (same distance), muscle fibers create changing force but does not move a load. Muscle length doesn’t change. Tendon collagen stretches out. • concentric– develops tension while shortening • eccentric– develops tension while lengthening *(most muscle actions are a combination of these)