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chapter 9

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Terms in this set (29)

  • Smooth muscle characteristics
    Not striated and involuntary muscle type.
  • Purpose of shivering and sitting upright
    Shivering produces heat; sitting upright maintains posture.
  • Connective tissue layers in muscle
    Epimysium: surrounds whole muscle; Perimysium: surrounds fascicles; Endomysium: surrounds individual muscle fibers.
  • What is one muscle fiber?
    A long, multinucleated cell formed by fused myoblasts; myosatellite cells repair damaged fibers.
  • Muscle cell membrane, cytoplasm, and ER names
    Sarcolemma: membrane; Sarcoplasm: cytoplasm; Sarcoplasmic reticulum: specialized ER.
  • Effect of ruptured tendon and aponeurosis definition
    Ruptured tendon means force cannot reach bone, so no movement; Aponeurosis is a broad, sheetlike tendon.
  • Role of T tubules, terminal cisternae, triad, and SR
    T tubules carry action potentials inward; terminal cisternae store Ca²⁺; triad = 1 T tubule + 2 terminal cisternae; SR stores/releases Ca²⁺.
  • Proteins in thin and thick filaments
    Thin: actin, troponin, tropomyosin; thick: myosin. Tropomyosin blocks sites; troponin binds Ca²⁺.
  • Sarcomere changes during contraction
    I band, H zone, and Z-to-Z distance shorten; A band length stays constant; overlap between filaments increases.
  • Resting ion concentrations and pump function
    Na⁺ high outside, K⁺ high inside; pump moves 3 Na⁺ out and 2 K⁺ in; Na⁺ enters during depolarization, K⁺ exits during repolarization.
  • Sequence of events at the neuromuscular junction (NMJ)
    Order: D, G, B, F, A, E, C (specific steps of NMJ signaling).
  • How does the NMJ signal end?
    AChE breaks down acetylcholine, closing receptors and allowing muscle fiber relaxation.
  • Excitation–contraction (E–C) coupling steps
    Action potential → T tubules → SR releases Ca²⁺ → Ca²⁺ binds troponin → tropomyosin moves → binding sites exposed.
  • ATP roles in muscle contraction
    ATP detaches myosin heads, hydrolysis re-cocks them, and powers Ca²⁺ pumping back into SR.
  • Effect if Ca²⁺ can't bind troponin or ACh receptors are blocked
    No cross-bridge formation → no contraction; blocked receptors cause weakness or paralysis.
  • Why is ATP needed for muscle relaxation?
    ATP powers SR Ca²⁺ pumps and Na⁺/K⁺ pumps; removing Ca²⁺ lets tropomyosin cover actin sites again.
  • Phases of a muscle twitch
    Latent (no tension), contraction (tension rises), relaxation (tension falls).
  • Why does calcium matter in wave summation and tetanus?
    Residual Ca²⁺ from previous stimuli allows tension to build with repeated stimulation.
  • What is a motor unit?
    One motor neuron plus all the muscle fibers it controls; smaller units allow finer control.
  • Two ways to increase muscle tension
    Increase stimulation frequency and recruit more motor units; small units recruited first.
  • Length–tension relationship in muscle
    Optimal filament overlap produces maximal tension; overstretched or over-shortened sarcomeres reduce force.
  • Types of muscle contraction during a bicep curl
    Concentric: lifting (shortening); eccentric: lowering (lengthening while active); isometric: holding (no length change).
  • Why is lowering a weight not muscle relaxation?
    Muscle remains active to resist gravity; this is an isometric contraction.
  • Why use phosphocreatine at sprint start?
    Stored ATP lasts ~2 seconds; phosphocreatine quickly regenerates ATP until glycolysis increases.
  • Causes of muscle fatigue
    Fatigue results from metabolites, ion imbalances, fuel depletion, and neural factors; low pH reduces Ca²⁺ binding.
  • Cori cycle and EPOC explained
    Lactate from muscle → blood → liver → glucose → muscle; EPOC is elevated oxygen use post-exercise to restore ATP and clear lactate.
  • Hypertrophy vs. atrophy
    Hypertrophy: muscle fibers grow with use; atrophy: fibers shrink with disuse, e.g., after casting a leg.
  • Diseases affecting muscle function: polio, botulism, myasthenia gravis
    Polio: motor neuron damage; botulism: blocks ACh release; myasthenia gravis: autoimmune loss of ACh receptors.
  • Difference between tetanus and rigor mortis
    Tetanus: infection causes spasms by disrupting neural inhibition; rigor mortis: no ATP after death prevents myosin detachment.