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1. Muscle Composition and Muscular Dystrophy.docx

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Kinesiology 2230A/B
Glen Belfry

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Muscle Pocket Hercules Height is 4’11, weight 135 lbs Can clean and jerk 418 lbs Skeletal Muscle Muscle Structure Muscle fibres are a single cells made up of myofibrils • There are more than 430 muscles in the body  Opposing pairs – agonist and antagonist muscles Fibre Types (twitch time = when the muscle is stimulated how long it takes to shorten/relax) So/ST: slow twitch fibres, predominately aerobic/oxidative FOG/FTa: faster twitch, both glycolytic and oxidative capacity  not producing as much lactate, advantageous to athletes FG/FTb: fast glycolytic fibres, largest fibres in cross sectional area, very little oxidative capacity Recruitment of fibres: use is related to the force required More recently they have started to differentiate the fast twitch fibres of animals vs humans (type 2x/2b) • The 2b fibres in the animal world are very glycolytic, zero oxidative capacity, whereas the 2x fibres in humans have a little oxidative capacity, not nearly as much as the 2a fibres Cardiac • Myocardium, heart muscle • Combination of nervous system and endocrine (epinephrine) system control Smooth • Involuntary, controlled unconsciously • In the walls of blood vessels and internal organs • Smooth muscle is relatively slow (in contraction) compared to cardiac and skeletal muscle  Takes a few seconds to change diameter  Recall local and peripheral stimulus factors Skeletal The two attachment sites are origin (non-moveable) and insertion (movable). Connective Tissue Anatomy Epymisium: tissue surrounding the whole muscle Perimysium: surrounds approximately 150 fibres Endomysium: separates individual fibres Fasciculus: whole group of fibres within perimysium The connective tissues from the epymisium – perimysium – Endomysium come together as the tendon that attaches to the bone • Connective tissue all coalesces in the tendon which transmits force to the bone • Gives transfer of force to bone to create shortening of muscle and movement around joint. Scaffolding Proteins • Scaffolding proteins (titin and nebulin) help muscles keep their shape • Scaffolding proteins gives you the support to generate tremendous strength without damaging the body and allowing transfer throughout the muscles and around the joint itself  Titin in myosin filament (thick)  Nebulin in actin filament (thin) Contract
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