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Muscle Tissue and Contraction - Anatomy & Physiology

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Terms in this set (22)

  • Main function of muscle tissue
    Convert chemical energy to mechanical energy to create movement and generate force.
  • Four properties of muscle tissue
    Contractility: forcibly shorten; Extensibility: ability to stretch; Elasticity: return to original length; Excitability: respond to stimuli.
  • Types of muscle tissue in the human body
    Skeletal, Cardiac, and Smooth muscle tissues.
  • Which muscle types are striated?
    Skeletal and Cardiac muscles are striated; Smooth muscle is non-striated.
  • Voluntary vs involuntary muscle control
    Skeletal muscle is voluntary; Cardiac and Smooth muscles are involuntary.
  • Largest muscle cell type
    Skeletal muscle cells are typically the largest muscle cells.
  • Organization of skeletal muscle tissue
    Muscle fibers bundled into fascicles, fascicles bundled into muscle, surrounded by connective tissues: endomysium, perimysium, and epimysium.
  • Connective tissue connections to bones
    Muscles connect to bones via tendon-like and aponeurosis-like structures.
  • Structure of a muscle fiber
    A long, multinucleated cell surrounded by the endomysium and plasma membrane called the sarcolemma.
  • What is a sarcomere?
    The smallest contractile unit of a muscle fiber, composed of actin and myosin filaments.
  • Sliding filament theory
    Muscle shortens as myosin (thick filament) pulls on actin (thin filament), increasing overlap without changing filament length.
  • Contractile proteins of the sarcomere
    Myosin (thick filament) and Actin (thin filament).
  • Regulatory proteins in muscle contraction
    Tropomyosin blocks myosin binding sites on actin; Troponin binds Ca+2 and moves tropomyosin to expose binding sites.
  • Structural protein in sarcomere
    Titin provides elasticity and helps sarcomere return to resting length.
  • Regions of the sarcomere
    Z disc: sarcomere boundary; M line: middle anchoring myosin; A band: length of myosin; I band: actin only; H zone: myosin only.
  • What shortens during muscle contraction?
    The sarcomere shortens; the I band and H zone decrease; A band length remains constant.
  • Role of the sarcoplasmic reticulum in contraction
    Stores and releases Ca+2 ions to trigger muscle contraction.
  • Excitation-contraction coupling
    Process where an action potential triggers Ca+2 release, exposing myosin binding sites and causing contraction.
  • Neurotransmitter at neuromuscular junction
    Acetylcholine (ACh) is released to stimulate muscle fiber contraction.
  • Phases of action potential in muscle fiber
    Depolarization: Na+ enters cell making inside positive; Repolarization: K+ exits restoring negative charge.
  • Cross-bridge cycle steps
    1) Myosin binds actin; 2) Power stroke pulls actin; 3) ATP binds myosin releasing actin; 4) ATP hydrolysis cocks myosin head.
  • Effect of ATP depletion on muscle contraction
    Myosin remains bound to actin causing muscle rigidity; contraction cannot continue.