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Sliding Filament Theory and the Sacromere definitions

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  • Sarcomere
    The fundamental unit of muscle contraction, composed of overlapping actin and myosin filaments.
  • Myosin
    A thick filament protein with heads that pull on actin to shorten the sarcomere during contraction.
  • Actin
    A thin filament protein that myosin pulls on to facilitate muscle contraction.
  • Tropomyosin
    A thread-like protein that blocks myosin binding sites on actin, regulating muscle contraction.
  • Troponin
    A globular protein that binds calcium, moving tropomyosin to allow myosin-actin interaction.
  • Titin
    An elastic filament protein that helps the sarcomere return to its original size post-contraction.
  • Z-disc
    The boundary of a sarcomere, anchoring actin filaments and marking the sarcomere's ends.
  • M-line
    The central line in a sarcomere that anchors myosin filaments.
  • I-band
    The light band in a sarcomere containing only actin filaments.
  • A-band
    The dark band in a sarcomere where actin and myosin overlap.
  • H-zone
    The central region of the A-band with only myosin, which diminishes during contraction.
  • Myofibril
    A cylindrical organelle within muscle cells, composed of repeating sarcomeres.
  • Sliding Filament Theory
    A model explaining muscle contraction by the sliding of actin over myosin, shortening the sarcomere.
  • Myosin Heads
    Protrusions on myosin filaments that bind to actin and pull it during contraction.
  • Sarcoplasmic Reticulum
    A structure that releases calcium to trigger muscle contraction by interacting with troponin.