02-05 Muscle Structure Function EXB101 F10

02-05 Muscle Structure Function EXB101 F10 - EXB 101...

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EXB 101: Exercise Physiology Lectures 2-5 Objectives Skeletal Muscle Structure and Function
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Objectives • To understand how energy is stored and utilized in the body at rest and during exercise. – Where does energy utilization occur? – How is energy stored? – How is energy generated? – What is metabolism? – What metabolic pathways are utilized during acute and chronic exercise? – How do skeletal muscles adapt to changes in activity?
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Exercise Metabolism
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The ability to use energy is the hallmark of all living organisms This energy, in the form of ATP, is found in all cells , but in small amounts ranging from 3 mmol/kg up to 6 mmol/kg in skeletal muscle. ATP is used to drive a number of processes: Making cell proteins Storing fuels Synthesizing RNA Transport of substrates Signaling to regulate cellular processes.
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Skeletal Muscle • ~660 skeletal muscles in the body • 45% of body weight • Primary Function: Force Generation • Secondary Functions: – Heat production – Glucose uptake and storage – Regulation of metabolic rate – Source of fuel (amino acids)
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Cellular components of muscle 75% water, 20% protein, 5% other • Contractile Tissue: Myosin, Actin • Connective Tissue: tendons, fascia • Vascular Tissue • Neural Tissue – Motor innervation: α -motoneurons, γ - motoneurons – Sensory receptors: muscle spindle, Golgi tendon organs, mechanoreceptors, nociceptors • Cellular organelles – Nucleus – Mitochondria – Ribosomes, Golgi Apparatus, Endoplasmic Reticulum
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Unique Features of Skeletal Muscle • Muscle cells are multinucleated – 200-300 nuclei per cubic mm • Muscle cells are capable of regeneration – Satellite cells • Muscle cells are very adaptable – Muscle fibers can alter their size throughout life in response to various stressors. – Muscle fibers can modify their metabolic properties in response to alterations in use.
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Epimysium Perimysium Endomysium (basement membrane, basal lamina) Plasma Membrane or Sarcolemma
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Muscle Fibers
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Skeletal Muscle Fibers The size of the fiber is determined by the number of myofibrils. Fiber cross-sectional area varies from 2000-7500 μ m 2 Fiber length varies from 3-4 mm to 30 cm – Fibers do not necessarily extend the entire length of the muscle. Muscle fibers are surrounded by 2 membranes – Basement membrane or basal lamina – Plasma membrane or sarcolemma
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Myonuclei: – Post-mitotic – Beneath sarcolemma – Periphery of fiber Satellite Cells: – Undifferenetiated
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02-05 Muscle Structure Function EXB101 F10 - EXB 101...

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