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Skeletal Muscle Contraction definitions

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  • Sarcomere
    Structural unit of muscle fiber whose length changes during contraction, with specific regions shrinking or remaining constant.
  • Sliding Filament Model
    Mechanism describing how thick and thin filaments interact to shorten muscle fibers without altering overall muscle volume.
  • H Zone
    Region within a sarcomere containing only thick filaments, which decreases in size during muscle contraction.
  • I Band
    Area of a sarcomere composed solely of thin filaments, narrowing as muscle contracts.
  • A Band
    Section of a sarcomere representing the length of thick filaments, remaining unchanged during contraction.
  • M Disc
    Central structure in the sarcomere toward which actin filaments are pulled during contraction.
  • Z Disc
    Boundary of a sarcomere anchoring actin filaments, moving closer to the center during contraction.
  • Actin
    Thin filament protein pulled toward the center of the sarcomere, enabling muscle shortening.
  • Myosin
    Thick filament protein whose head interacts with actin to drive muscle contraction through cyclic movements.
  • Actomyosin Cycle
    Five-step biochemical process involving ATP and filament interactions, resulting in sarcomere contraction.
  • Troponin
    Regulatory protein binding calcium, triggering a conformational change that exposes binding sites for contraction.
  • Tropomyosin
    Long regulatory protein blocking binding sites on actin, preventing contraction until shifted by troponin.
  • Sarcoplasmic Reticulum
    Membranous organelle in muscle cells responsible for storing and releasing calcium to regulate contraction.
  • Calcium
    Ion released upon nervous stimulation, binding to troponin and enabling muscle contraction by exposing binding sites.
  • Power Stroke
    Movement of the myosin head that shifts actin toward the center of the sarcomere, driving muscle contraction.