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IUPUI BIOL 261 - Anatomy Notes Exam 3

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Anatomy Notes Exam 3 Skeletal- single, long and cylindrical striated cells, multinucleate, voluntarily Cardiac- one nucleus per cell (bi), involuntarily Smooth- walls of hallow organs, single fusiform nonstriated cells, uninucleate, involuntaryShared spec. properties: excitability, contractility, elasticity, extensibility Function. of skeletal muscle: movement, body position & posture, support soft tissue, reg. entrance & exit of materials, heat generation, joint stabilizationG. anatomy: skeletal muscle surrounded by epimysium, comprised of bundles of muscle fascicles. Muscle fascicle- group of muscle fibers surrounded by perimysium. Muscle fiber- highly elongated cell (NO CARDIAC) comprised of myofibrils surrounded by endomysiumSarcolemma- plasma membrane of muscle fiber (comprised of abundant myofibrils)Sarcoplasm- cytoplasm of muscle fiber (myofibrils)Myofibril- cylindrical structure surrounded by SR, responsible for contraction of skeletal muscle fiber *arranges parallel to the long axis of the cell with s arranged side to side (distinct light & light bands)SR- controlling contraction of individual myofibrils via release of calcium ionsT tubules- deep invaginations of sarcolemma, allow electrical impulses to travel to interior of cellTerminal cisternae- expanded chambers on either side of a transverse tubule where the tubule of SR has enlarged and fusedTriad- combination of a pair of terminal cisternae + t tubule Sarcomere- myofibrils consist of sarcomeres, repeating units of myofilaments Myofilaments- generate contractile force, determine the striation pattern in skeletal muscle fibers M line- link thick filaments that lie in the center of the sarcomere Z lines- open meshwork of interconnecting proteins called ACTINS, occur where thin filaments from adjacent sarcomeres joinZone of overlap- thin filaments pass between the thick filaments A band- contain thick filaments including the m line, h band, and zone “dark”H band- area containing thick filaments onlyI band- area containing thin filaments only “light”During contraction, z lines move closer together & the I bands and H bands shorten THIN FILAMENTS: F actin- a strand of 300-400 globular G actin moleculesNEBULIN- a slender strand of proteins that holes the f actin strand together G actin- contains an active site that can bind to a thick filament in the same manner that a substrate molecule binds to an enzymes active site

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