physiology of skeletal muscle

physiology of skeletal muscle - Physiology of Skeletal...

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Unformatted text preview: Physiology of Skeletal Muscle o Skeletal Muscle structure Sarcomere-smallest contractile unit containing thin and thick filaments Muscle fiber-single cell containging many sarcomeres in series Sarcolemma-surrounds each muscle fiber Fasiculi-bindles of muscle fibers which are grouped to form a whole muscle o Motor Unit Motor nerve cell + dividing axon + all the muscle fibers innervated 100: I - 600: 1 ratio of muscle fibers per nerve Precision muscles - small motor units (ocular) Power muscles - large motor units (gastrocnemeus) All - or - None Law o Similar to nerves-Threshold vs. sub-threshold vs. suprathreshold =Minimal vs. Maximal stimuli-"graded responses" due to muscle fiber recruitment RecruitmentIF orce Gradation o Each muscle fiber produces a constant amount of force when activated.-tr the task requires more force:-Recruit more motor units.-Increase frequency o{stimulation-t stimulus = t active motor units = t force tension E-C Coupling-':" " 1 ' ' ,,' ",,,, ..,-,,.'.,,,,,, Excitation-Contraction (E-C) Coupling o EC coupling is the physiologic mechanism where an electrical discharge at the muscle initiates chemical events at the cell surface leading to intracellular Ca+2 release and ultimately a muscle contraction =From nerve to muscle Excitation-Contraction Coupling o AP in neuron reaches axon terminal and causes the release of ACh into synapse (neuromuscluar juntion) ACh receptors in motor end plate transmit AP across surface of muscle cell and down T-tubules .Ca++ is released from SR and binds wi troponin and exposes cross-bridge binding site on actin-Myosin cross bridge binds to actin and "power stroke" occurs (ratcheting effect) .ATP binds to cross bridge and breaks bond between actin and myosin-Filaments return to resting position - if enough Ca++ is available within cell, another cycle can occur Profile of a Sarcomere Sure. )1l1C1T Sliding Filament Theory...
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physiology of skeletal muscle - Physiology of Skeletal...

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