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Muscle Tissue Structure and Function - Anatomy & Physiology

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Termini in questo insieme (20)

  • Layers of connective tissue in skeletal muscle
    Epimysium surrounds entire muscle, Perimysium surrounds fascicles, Endomysium surrounds individual muscle fibers.
  • Definition of a muscle fascicle
    A bundle of muscle fibers surrounded by perimysium connective tissue.
  • Structure of a muscle fiber
    A muscle fiber is a single muscle cell, surrounded by sarcolemma, containing many myofibrils.
  • Function of the sarcolemma
    The muscle cell membrane that encloses the sarcoplasm and conducts action potentials.
  • Role of myofibrils in muscle fibers
    Myofibrils are bundles of protein filaments responsible for muscle contraction.
  • Basic contractile unit of muscle
    The sarcomere, which extends from one Z line to the next.
  • Components of a sarcomere
    Contains thick filaments (myosin), thin filaments (actin), Z lines, M line, H zone, I band, and A band.
  • Function of the Z line in sarcomeres
    Defines the boundary between adjacent sarcomeres and anchors thin filaments.
  • Difference between A band and I band
    A band contains thick filaments and overlapping thin filaments; I band contains only thin filaments.
  • Role of the H zone
    Central region of the A band with only thick filaments, no thin filament overlap.
  • Structure of thick filaments
    Composed mainly of myosin molecules with heads that form cross-bridges during contraction.
  • Structure of thin filaments
    Made of F actin strands, tropomyosin, troponin complex, and nebulin.
  • Function of tropomyosin and troponin
    Tropomyosin blocks active sites on actin; troponin binds calcium to move tropomyosin and expose active sites.
  • Sliding filament model of contraction
    Myosin heads bind to actin active sites, pivot, and slide thin filaments past thick filaments to shorten sarcomeres.
  • Role of calcium ions in muscle contraction
    Ca2+ binds to troponin, causing tropomyosin to move and expose actin active sites for myosin binding.
  • Function of transverse (T) tubules
    Transmit action potentials deep into muscle fibers to trigger calcium release from the sarcoplasmic reticulum.
  • Role of sarcoplasmic reticulum in muscle fibers
    Stores and releases Ca2+ to initiate muscle contraction.
  • Definition of a motor unit
    A motor neuron and all the muscle fibers it innervates, contracting together.
  • All-or-none principle in muscle contraction
    Individual muscle fibers contract fully or not at all when stimulated.
  • Difference between isotonic and isometric contractions
    Isotonic changes muscle length with constant tension; isometric develops tension without changing length.