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Musculoskeletal System quiz #1

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  • Explain the sliding filament model of muscle contraction, including the roles of actin, myosin, troponin, tropomyosin, ATP, and calcium.
    The sliding filament model describes how muscles contract by the sliding of actin (thin) and myosin (thick) filaments within sarcomeres. Normally, myosin binding sites on actin are blocked by tropomyosin. When calcium is released from the sarcoplasmic reticulum (triggered by an action potential), it binds to troponin, causing tropomyosin to move and expose the binding sites. Myosin heads, with ATP bound, attach to actin. ATP is hydrolyzed, powering the 'power stroke' that pulls actin past myosin. After the stroke, myosin releases ADP, binds a new ATP, detaches, and the cycle repeats, resulting in muscle contraction.
  • Differentiate between fast-twitch and slow-twitch muscle fibers in terms of their function, energy use, and fatigue resistance.
    Fast-twitch muscle fibers contract rapidly and are used for quick, powerful movements but fatigue quickly because they rely mainly on glycolysis for ATP. Slow-twitch fibers contract more slowly, are used for endurance activities, and resist fatigue because they use aerobic respiration for ATP and contain more myoglobin to store oxygen.
  • What are the main components of the musculoskeletal system and their primary functions?
    The musculoskeletal system consists of muscles, which contract to produce movement, and the skeleton, which provides structural support and protection for organs.
  • Describe the structure and function of a sarcomere in muscle contraction.
    A sarcomere is the contractile unit of a muscle fiber, composed of actin (thin) and myosin (thick) filaments that slide past each other to shorten the muscle during contraction.
  • Explain the role of calcium in the sliding filament model of muscle contraction.
    Calcium is released from the sarcoplasmic reticulum in response to an action potential, binds to troponin, and causes tropomyosin to move, exposing myosin binding sites on actin.
  • How does ATP contribute to the muscle contraction cycle?
    ATP binds to myosin heads, allowing them to attach to actin; its hydrolysis powers the 'power stroke,' and a new ATP molecule is needed for myosin to detach and repeat the cycle.
  • Differentiate between fast-twitch and slow-twitch muscle fibers in terms of contraction speed and energy use.
    Fast-twitch fibers contract quickly and rely mainly on glycolysis for ATP, leading to rapid fatigue, while slow-twitch fibers contract slowly, use aerobic respiration, and are more resistant to fatigue.
  • What is the function of myoglobin in muscle fibers?
    Myoglobin is an oxygen-binding protein in muscle fibers that stores oxygen for use during periods of high demand, especially in slow-twitch fibers.
  • Describe the difference between tendons and ligaments in the musculoskeletal system.
    Tendons connect muscles to bones, enabling movement, while ligaments connect bones to other bones, stabilizing joints.
  • How do antagonistic muscle pairs, such as the biceps and triceps, facilitate movement?
    Antagonistic muscle pairs work in opposition; when one (the flexor) contracts to bend a limb, the other (the extensor) contracts to straighten it.