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Vertebrate Functional Morphology BSC 400/500 Muscles (Chapter 10): Muscle Functions: Supply force for movement and together with the skeletal system, they allow an animal to act Restrain movement, by keeping the body in place Surround visceral organs, blood vessels, respiratory channels, and glands and influence their activities Form sphincters that control the passage of material through tubular structures Produce heat for thermoregulation (shivering) Produce electrical energy o Electric organs (specialized group of muscles developed by some fish) – can generate strong bursts of electrical energy that can paralyze prey o Used as protection Muscle Types: Skeletal Muscle = musculature attached to bones, body movement o Striated, Voluntary – controlled by somatic motor neurons o Structure: Make up 40% of body mass Derived mostly from myotomes of embryo and develop from end to end fusion of many myoblasts Attach to bones by collagenous tendons Contain an origin and insertion Inside muscles are bundles of muscle fibers, connective tissue, blood vessels, and nerves Entire muscle is wrapped in a connective tissue sheath that is continuous with the fascia and tendons Muscle cells = largest cells of the body, extend the length of the muscle, and referred to as muscle fibers Membrane = sarcolemma and the cytoplasm sacroplasm Each muscle fiber is composed of a bundle of contractile units called myofibrils Muscle fibers = multinucleated and myofibrils composed of 2 filamentous proteins: Actin (the thin filament) and myosin (the thick filament) o Offset orientation of actin and myosin filaments show alternating light and dark bands when muscle fibers view under microscope striated appearance o Actin and myosin arranged in units called sacromeres = functional
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unit of the muscle, bounded by Z lines on each side Regions: A band = myosin (thick) filaments stacked along with parts of actin (thin) filaments H zone = middle of the A band where actin doesn’t reach M line = extends vertically down the center of the A band I band = has part of actin that don’t project into A band Sarcoplasmic Reticulum = smooth endoplasmic reticulum inside muscle cells Surrounding the cells is a duct-work set of tubes called T-tubules or Transverse tubules Cells connected to the nervous system by way of neuromuscular junctions = sites where a nerve’s terminal axon is aligned with the motor endplate of the muscle fiber Cardiac Muscle = musculature of the heart o Striated, Involuntary – controlled by intrinsic system, autonomic nervous system, and hormones o Structure/Function: Cardiac muscle only found in the heart and is composed of moderately elongated fibers possessing a single nucleus that frequently branches Myofilaments are also arranged to give striated appearance Individual cells are connected end to end at specialized junctions called intercalated disks
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This note was uploaded on 04/29/2010 for the course BIOL 1404 taught by Professor Machaeldini during the Fall '09 term at Texas Tech.

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