Muscle Physiology: Muscle Fiber Contraction
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Questions and Answers

What happens to the mechanical response of a muscle fiber when the frequency of action potentials is increased?

  • It decreases beyond the level of maximal tetanic tension
  • It remains constant
  • It increases up to the level of maximal tetanic tension (correct)
  • It decreases
  • At what load does the maximum velocity of muscle fiber shortening occur?

  • At zero load (correct)
  • At 50% of maximum load
  • At minimum load
  • At maximum load
  • What is the primary source of fuel for muscle fibers at the beginning of exercise?

  • Muscle glycogen (correct)
  • Fatty acids from the blood
  • Glucose from the blood
  • Creatine phosphate
  • What is the primary mechanism of ATP formation in the mitochondria of muscle fibers?

    <p>Oxidative phosphorylation</p> Signup and view all the answers

    What is the optimal sarcomere length for generating maximum isometric tetanic tension?

    <p>Lo</p> Signup and view all the answers

    What is a contributing factor to muscle fatigue during high-intensity exercise?

    <p>Increase in H+ concentration</p> Signup and view all the answers

    What is the primary mechanism by which muscle tension is increased?

    <p>Recruiting additional motor units in a muscle</p> Signup and view all the answers

    What type of exercise increases a fiber's capacity for oxidative ATP production?

    <p>Long-duration, low-intensity exercise</p> Signup and view all the answers

    Which type of motor unit is recruited first during muscle contraction?

    <p>Slow-oxidative motor units</p> Signup and view all the answers

    What is the result of increased synthesis of actin and myosin in muscle fibers?

    <p>Increased strength</p> Signup and view all the answers

    What is the primary function of antagonistic muscles around a joint?

    <p>To flex and extend a limb</p> Signup and view all the answers

    What type of muscle contraction is characterized by a high velocity of movement?

    <p>Contraction with high motor-unit recruitment</p> Signup and view all the answers

    What is the primary reason why muscle tension is greater than the load in an isometric contraction?

    <p>To compensate for the mechanical disadvantage of the lever system</p> Signup and view all the answers

    What is the primary cause of hypocalcemic tetany?

    <p>Decreased extracellular Ca2+ concentration</p> Signup and view all the answers

    What is the role of calcium ions in sodium channels?

    <p>To interact with the exterior surface of sodium channels to regulate their opening</p> Signup and view all the answers

    What is the primary defect in muscular dystrophies?

    <p>Defects in muscle-membrane-stabilizing proteins</p> Signup and view all the answers

    What is the primary effect of heavy exercise on muscle contraction?

    <p>Involuntary tetanic contractions</p> Signup and view all the answers

    What is the primary mechanism of muscle contraction in the lever system?

    <p>Isometric contraction</p> Signup and view all the answers

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