Muscle Contraction Process Quiz
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Questions and Answers

What happens when Ca2+ binds to troponin in muscle contraction?

  • Voltage-sensitive tubule proteins return to their original shape.
  • Troponin changes shape, exposing myosin binding sites on the thin filaments. (correct)
  • Myosin-actin interaction is inhibited.
  • Tropomyosin blocks active sites on actin.

    • What initiates the cross bridge cycling in muscle contraction?

  • Tropomyosin blocking active sites.
  • Myosin binding to actin. (correct)
  • Ca2+ being pumped back into the SR.
  • Voltage-sensitive tubule proteins changing shape.

    • What occurs when the muscle action potential ceases in terms of calcium levels?

  • Ca2+ is released from the SR to the cytosol. (correct)
  • Ca2+ release channels of the SR remain open.
  • Ca2+ levels in the sarcoplasm rise.
  • Ca2+ is continually pumped back into the sarcoplasm.

    • What happens when Ca2+ levels are low in muscle contraction?

    <p>Tropomyosin blocks active sites on actin.</p> Signup and view all the answers

    What leads to relaxation in muscle fibers during contraction?

    <p>Tropomyosin unblocking active sites.</p> Signup and view all the answers

    What occurs each time an action potential arrives at the neuromuscular junction?

    <p>The voltage-sensitive tubule proteins change shape.</p> Signup and view all the answers

    What happens when Ca2+ is absent in muscle contraction?

    <p>Relaxation occurs</p> Signup and view all the answers

    During excitation-contraction (E-C) coupling, where does the action potential propagate?

    <p>Along the sarcolemma and T tubules</p> Signup and view all the answers

    Which protein blocks active sites on actin in muscle contraction?

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

    What leads to the sliding of myofilaments during muscle contraction?

    <p>Binding of troponin and myosin</p> Signup and view all the answers

    In which step of excitation-contraction (E-C) coupling are calcium ions released?

    <p>From the terminal cistern of SR</p> Signup and view all the answers

    What happens to myosin-actin interaction if tropomyosin is blocking the active sites?

    <p>It is inhibited</p> Signup and view all the answers

    What is the role of ATP in muscle contraction?

    <p>ATP hydrolysis energizes the myosin head for cross bridge formation</p> Signup and view all the answers

    How does higher intracellular calcium concentration contribute to muscle contraction?

    <p>Ca2+ binds to troponin, triggering a shift in tropomyosin, allowing myosin and actin interaction</p> Signup and view all the answers

    What happens during the working (power) stroke in the cross bridge cycle?

    <p>Myosin heads pivot and pull thin filaments toward the center of the sarcomere</p> Signup and view all the answers

    What is the function of tropomyosin in muscle contraction?

    <p>Tropomyosin blocks myosin-binding sites on actin filaments at rest</p> Signup and view all the answers

    What causes cross bridge detachment in the sarcomere?

    <p>ADP and Pi bind to myosin heads, causing them to release from actin</p> Signup and view all the answers

    In the context of muscle contraction, what does troponin do?

    <p>Troponin binds Ca2+ and triggers a conformational change in tropomyosin</p> Signup and view all the answers

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