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بنام خدا

بنام خدا. Speed of contraction:. Energy Sources. ATP provides immediate energy for muscle contractions from 3 sources Creatine phosphate During resting conditions stores energy to synthesize ATP Anaerobic respiration

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بنام خدا

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  1. بنام خدا

  2. Speed of contraction:

  3. Energy Sources • ATP provides immediate energy for muscle contractions from 3 sources • Creatine phosphate • During resting conditions stores energy to synthesize ATP • Anaerobic respiration • Occurs in absence of oxygen and results in breakdown of glucose to yield ATP and lactic acid • Aerobic respiration • Requires oxygen and breaks down glucose to produce ATP, carbon dioxide and water • More efficient than anaerobic

  4. Slow and Fast Fibers • Slow-twitch or high-oxidative • Contract more slowly, smaller in diameter, better blood supply, more mitochondria, more fatigue-resistant than fast-twitch • Fast-twitch or low-oxidative • Respond rapidly to nervous stimulation, contain myosin to break down ATP more rapidly, less blood supply, fewer and smaller mitochondria than slow-twitch • Distribution of fast-twitch and slow twitch • Most muscles have both but varies for each muscle • Effects of exercise • Hypertrophies: Increases in muscle size • Atrophies: Decreases in muscle size

  5. Myosin-regulated contraction Ca2+ entry and release from SR Ca2+-CaM-MLCK-dependent phosphorylation of myosin light chains . crossbridge cycling Contraction

  6. Relaxation in smooth muscle [Ca2+] decreases Ca channels close RyR close CaM-MLCK activity decr. Phosphatase dephosphorylates MLC Relax

  7. Smooth muscle contracts slowly and efficiently. Blood vessels GI tract lung airways

  8. Smooth muscle can contract without change in voltage: hormones and drugs activate IP3 production and Ca2+ release from SR.

  9. Regulation of Arteriolar Smooth Muscle Constriction Sympathetic: norepinephrine released  receptor receptor splanchnic and skin Antidiuretic hormone/vasopressin Angiotensin II

  10. Regulation of Arteriolar Smooth Muscle Dilation Sympathetic: epinephrine receptor muscle, heart, liver Parasympathetic: ACh Endothelia respond by producing NO Reduce norepinephrine output EDRF - NO Histamine - mast cells Adenosine - low [O2] Lactic acid, high [K+] and metabolites?

  11. Smooth Muscle Regulation • Innervated by autonomic nervous system • Neurotransmitter are acetylcholine and norepinephrine • Hormones important as epinephrine and oxytocin • Receptors present on plasma membrane which neurotransmitters or hormones bind determines response

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