Muscle Physiology: Skeletal Contraction
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Questions and Answers

Which type of muscle fiber has a higher resistance to fatigue?

  • Type II fibers
  • Type I fibers (correct)
  • Type III fibers
  • Type IV fibers

    • What is the primary storage fuel for Type II muscle fibers?

  • Glucose
  • Glycogen (correct)
  • Protein
  • Fat

    • Which of the following characteristics is NOT associated with Type I muscle fibers?

  • Large mitochondrial volume
  • High amounts of oxidative enzymes
  • Extensive sarcoplasmic reticulum (correct)
  • High myoglobin content

    • Which type of activity is primarily associated with Type I muscle fibers?

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

    What type of muscle fibers are the external ocular muscles primarily composed of?

    <p>Type II fibers</p> Signup and view all the answers

    What distinguishes Type II fibers from Type I fibers in terms of enzyme composition?

    <p>Higher glycolytic enzymes in Type II fibers</p> Signup and view all the answers

    Which characteristic is true about Type II muscle fibers in comparison to Type I fibers?

    <p>They are larger in size.</p> Signup and view all the answers

    What is the primary reason Type I fibers have a higher myoglobin content compared to Type II fibers?

    <p>To support aerobic metabolism</p> Signup and view all the answers

    What is the primary difference between muscle groups with fast fibers and those with slow fibers?

    <p>Fast fibers produce a greater velocity and more force compared to slow fibers.</p> Signup and view all the answers

    How does aging affect muscle fiber composition?

    <p>Results in a loss of fast fibers and an increase in slow fibers.</p> Signup and view all the answers

    What happens to muscle tension during tetanus?

    <p>It develops about four times that of individual twitch contractions.</p> Signup and view all the answers

    What characterizes isometric contraction?

    <p>There is no change in external muscle length, but tension increases.</p> Signup and view all the answers

    What is the role of calcium ions during muscle stimulation?

    <p>They are involved in the release for continuous cross-bridge cycling.</p> Signup and view all the answers

    What does the maximal stimulus do to muscle fibers?

    <p>Activates all muscle fibers.</p> Signup and view all the answers

    What occurs during the staircase phenomenon?

    <p>Free calcium ions in the myofibrils remain continuously high.</p> Signup and view all the answers

    Which athlete classification has a higher percentage of slow muscle fiber composition?

    <p>Distance runners with 70% slow fibers.</p> Signup and view all the answers

    What characterizes muscle fatigue?

    <p>Inability to maintain muscle work</p> Signup and view all the answers

    What is primarily responsible for muscle fatigue during exercises lasting 10-180 seconds?

    <p>Lactic acid accumulation</p> Signup and view all the answers

    Which statement about isometric and isotonic contractions is correct?

    <p>Isometric contractions maintain muscle length while isotonic contractions change length.</p> Signup and view all the answers

    What happens to the muscle contraction duration when fatigue occurs?

    <p>It prolongs.</p> Signup and view all the answers

    What factor contributes to muscle fatigue by interrupting blood flow?

    <p>Diminished oxygen supply</p> Signup and view all the answers

    Which factor does NOT affect muscle contraction during exercise?

    <p>Type of nutrients ingested</p> Signup and view all the answers

    In exercises longer than one hour, what is a primary cause of fatigue?

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

    What effect does lactic acid accumulation have on muscle function?

    <p>Decreases pH, affecting muscle contraction</p> Signup and view all the answers

    What is the effect of increasing the initial length of the muscle fibre beyond 2.2 μ on tension development?

    <p>It decreases tension development.</p> Signup and view all the answers

    Which type of contraction occurs when muscle tension remains constant while the muscle shortens to lift a weight?

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

    What defines the term 'afterload' in muscle contraction?

    <p>The load encountered only after the muscle starts to contract.</p> Signup and view all the answers

    What happens to the velocity of shortening as afterload increases during isotonic contraction?

    <p>It decreases.</p> Signup and view all the answers

    What happens to mechanical efficiency when no external work is done by the muscle?

    <p>It equals zero.</p> Signup and view all the answers

    Which statement is true regarding isometric contraction?

    <p>The muscle maintains posture against gravity.</p> Signup and view all the answers

    How does sarcomere length below 2.2 μ affect tension during isometric contraction?

    <p>It decreases tension development.</p> Signup and view all the answers

    What is the relationship between the load moved and external work during isotonic contraction?

    <p>No external work is done, regardless of load.</p> Signup and view all the answers

    Study Notes

    Skeletal Muscle Contraction

    • Skeletal muscle contraction is a complex process influenced by various factors.

    Muscle Fiber Types

    • Fast twitch fibers (Type 2a or 2b): Anaerobic, pale color, low blood supply, fatigue rapidly, fewer capillaries and mitochondria. Sprinter.
    • Slow twitch fibers (Type 1): Aerobic, red color, high blood supply, fatigue slowly, many capillaries and mitochondria. Marathon runner.

    Factors Affecting Muscle Contraction

    • Type of Muscle Fibers: Different fiber types have varying properties that affect their function in different activities.
    • Stimulus Strength: Increasing stimulus strength increases the number of activated fibers (recruitment). Maximum stimulus activates all fibers. Beyond that, further increases don't increase the response.
    • Stimulus Frequency: Increasing the frequency of stimulation leads to stronger contraction by releasing more calcium. Repeated stimulation can lead to a sustained contraction (tetanus).
    • Staircase Phenomenon: Repeated stimulation of a muscle results in a progressively increasing force of contraction.
    • Isometric Contraction: Muscle contracts but does not shorten. Tension increases. Initial muscle length impacts tension development.
    • Isotonic Contraction: Muscle contracts and shortens, maintaining constant tension. Velocity of shortening decreases as afterload increases.
    • Preload: The load a muscle experiences before contraction begins.
    • Afterload: The load a muscle experiences after contraction begins.

    Muscle Fatigue

    • Fatigue is the inability to sustain muscle work.
    • Causes of fatigue: Metabolites (e.g., lactic acid), glycogen depletion, decrease in oxygen, and diminished neuromuscular junction transmission.
    • Characterized by decreased strength, prolonged duration, and incomplete relaxation.
    • Duration of exercise impacts the cause of fatigue.

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    Description

    This quiz explores the intricate process of skeletal muscle contraction, focusing on muscle fiber types and the factors influencing contraction strength. Understand the differences between fast and slow twitch fibers, as well as how stimulus strength and frequency impact muscle performance. Perfect for students studying human physiology or sports science.

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