Muscle Fiber Types and Metabolism
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Muscle Fiber Types and Metabolism

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Questions and Answers

Which pathway is primarily responsible for ATP production during short bursts of intense exercise?

  • Oxidative phosphorylation
  • Krebs cycle
  • Anaerobic glycolysis
  • Creatine phosphate transfer (correct)

    • What is the main advantage of oxidative phosphorylation compared to anaerobic glycolysis?

  • It produces ATP without oxygen.
  • It generates a greater number of ATP molecules per glucose molecule. (correct)
  • It occurs entirely within the cytoplasm.
  • It requires less time to commence ATP production.

    • Which of the following correctly describes muscle fiber types in terms of their energy use?

  • Type I fibers primarily use glycolysis for energy.
  • Type I fibers are adapted for aerobic activity and rely on oxidative phosphorylation. (correct)
  • Type II fibers are low in myoglobin content and rely mainly on aerobic metabolism.
  • Type II fibers have high endurance and rely on oxidative phosphorylation.

    • What occurs during muscle hypertrophy?

    <p>Increase in muscle fiber size due to resistance training.</p> Signup and view all the answers

    How does the motor control system adapt during prolonged exercise?

    <p>It reduces the recruitment of motor units to conserve energy.</p> Signup and view all the answers

    What is the primary difference between oxidative fibers and glycolytic fibers?

    <p>Oxidative fibers have a higher capacity for ATP synthesis and are more fatigue-resistant.</p> Signup and view all the answers

    What triggers muscle hypertrophy?

    <p>Enhanced synthesis of myosin and actin due to testosterone.</p> Signup and view all the answers

    Which of the following is true regarding skeletal muscle tone?

    <p>Muscle tone is a low-level state of tension even at rest.</p> Signup and view all the answers

    What type of muscle fiber conversion is possible?

    <p>Fast-glycolytic fibers can be converted to fast-oxidative fibers.</p> Signup and view all the answers

    What distinguishes voluntary movements from reflexes?

    <p>Voluntary movements can be initiated and terminated at will.</p> Signup and view all the answers

    What occurs as a result of denervation atrophy?

    <p>Significant muscle shrinkage and tissue loss.</p> Signup and view all the answers

    Which motor activity is characterized by repetitive patterns?

    <p>Rhythmic activities.</p> Signup and view all the answers

    During isotonic contractions, what remains constant while the muscle changes length?

    <p>The load</p> Signup and view all the answers

    Which type of muscle contraction involves a muscle developing tension without changing length?

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

    What characterizes concentric contractions regarding load and velocity?

    <p>Higher load results in lower velocity</p> Signup and view all the answers

    Which statement accurately describes eccentric contractions?

    <p>The muscle lengthens while lowering an object</p> Signup and view all the answers

    In the context of muscle metabolism, glycolysis primarily occurs in which cellular compartment?

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

    Which of the following best describes oxidative phosphorylation?

    <p>A pathway dependent on the electron transport chain</p> Signup and view all the answers

    Which type of muscle fiber is primarily engaged in endurance activities?

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

    What is the primary characteristic of muscle hypertrophy?

    <p>Increased muscle fiber size</p> Signup and view all the answers

    What primarily causes muscle atrophy?

    <p>Inactivity or immobilization</p> Signup and view all the answers

    Which motor control mechanism primarily regulates voluntary movements?

    <p>Cerebral cortex</p> Signup and view all the answers

    Study Notes

    Muscle Fiber Types

    • Fast twitch fibers are defined by higher ATP-splitting activity, also known as myosin ATPase activity.
    • Different muscle fibers have different ATP-synthesizing abilities.
    • Oxidative fibers produce more ATP through oxidative phosphorylation than glycolytic fibers which makes them more resistant to fatigue.
    • The genetic endowment of muscle fibers varies, not only among individuals but also within muscles of one individual.
    • It is possible to induce changes in muscle fibers, specifically in their oxidative capacities and diameters.

    Muscle Metabolism and Fiber Types

    • The body has 3 primary pathways for synthesizing ATP during muscle contraction.
      • Transferring a high-energy phosphate from creatine phosphate to ADP
      • Oxidative phosphorylation
      • Anaerobic glycolysis
    • Creatine phosphate is the first energy store used at the onset of muscle activity. It provides energy to ADP in order to form ATP.

    Control of Motor Movement

    • A nervous system command to contract a motor neuron, triggers a contraction of all skeletal muscle fibers within its motor unit.
    • Human motor activity is typically categorized as reflex, voluntary, or rhythmic.
    • Reflexes are automatic responses to stimuli that do not require conscious effort.

    Withdrawal Reflex

    • An example of a reflex. A painful stimulus causes a withdrawal of a limb.

    Crossed Extensor Reflex

    • A postural reflex that stabilizes the body when a withdrawal reflex occurs.
    • It ensures that the opposite limb is in a position to bear weight.

    Muscle Tone

    • Muscle tone is the constant, involuntary, low-level tension within a muscle.
    • This helps to maintain postural stability.
    • There are 2 contributing factors to muscle tone:
      • Elasticity of the muscle
      • Muscle physiology

    Types of Contraction

    • Isotonic: The muscle changes length while the load remains constant. It's like when you lift an object.
    • Isokinetic: The muscle changes length while the velocity of shortening remains constant. This is often found in exercise machines.
    • Isometric: The muscle contracts but does not change length. This occurs when you hold a weight in a fixed position or maintain posture.

    Concentric and Eccentric Contractions

    • Concentric: The muscle shortens, and the higher the load, the lower the velocity at which the muscle fiber shortens.
    • Eccentric: The muscle lengthens. This is like lowering a book to place it on a desk. There is a direct relationship between eccentric contraction velocity and load.

    Lever Systems: Muscles, Bones, and Joints

    • Bones act as levers; joints act as fulcrums (pivot points).
    • Muscle insertion points are often situated farther from the joint, resulting in a mechanical disadvantage. For example, the bicep muscle must exert a force 7 times greater than the load to lift a weight.

    Motor Units

    • A motor unit consists of one motor neuron and all the muscle fibers that it innervates.

    Twitch Summation

    • When a muscle fiber receives a single action potential (AP), it produces a twitch.
    • Two twitches from two APs can sum together to produce greater tension than one.
    • This happens because an AP is much shorter than the duration of a twitch.

    Twitch Summation and Tetanus

    • As the frequency of APs increases, the amount of tension produced by the muscle fiber increases until it reaches a maximum (tetanus).

    Length-Tension Relationship

    • The optimal muscle length for generating the maximum amount of tension is Io.
    • This is the length where the overlap between myosin cross-bridges and actin's binding sites is optimal.

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    Related Documents

    Muscle Physiology II (Contraction) PDF

    Description

    This quiz explores the various types of muscle fibers, focusing on their ATP-synthesizing abilities and metabolic pathways. Understand the differences between fast-twitch and oxidative fibers, as well as the role of creatine phosphate in muscle contraction. Test your knowledge of muscle metabolism and the control of motor movement.

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