Muscle Contraction and Sarcomere Shortening Quiz
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Questions and Answers

What is the functional unit of the myofibril in a cardiac muscle fiber?

  • M-line
  • Z-line
  • Sarcomere (correct)
  • I-band

    • What is the role of the intercalated discs in cardiac muscle fibers?

  • Act as sites for energy production
  • Regulate oxygen intake
  • Allow for rapid communication between adjacent cells (correct)
  • Store excess calcium ions

    • What gives cardiac muscle fibers their striated appearance?

  • Golgi apparatus
  • Mitochondria
  • Myofibrils (correct)
  • Endoplasmic reticulum

    • How are cardiac muscle fibers different from skeletal muscle fibers?

    <p>Presence of T-tubules and intercalated discs in cardiac muscle fibers</p> Signup and view all the answers

    What is the significance of the central nucleus in a cardiac myocyte?

    <p>Provides genetic material for protein synthesis</p> Signup and view all the answers

    Which cellular structure is responsible for storing and releasing intracellular calcium ions during muscle contraction?

    <p>Sarcoplasmic reticulum</p> Signup and view all the answers

    What is the role of tropomyosin in muscle contraction?

    <p>Inhibit the interaction between actin and myosin</p> Signup and view all the answers

    Which subunit of troponin binds the entire troponin molecule to tropomyosin?

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

    What induces a conformational shift in tropomyosin, exposing the active sites on the actin filament?

    <p>Binding of calcium by TnC</p> Signup and view all the answers

    What is the composition of each myosin molecule?

    <p>Two globular heads and a rod-like tail</p> Signup and view all the answers

    What is the function of the myosin heads during muscle contraction?

    <p>Bind ATP and G-actin forming cross bridges</p> Signup and view all the answers

    How does binding of calcium ions contribute to muscle contraction?

    <p>Exposes active sites on G-actin for myosin binding</p> Signup and view all the answers

    What is the main function of the Transverse (T) tubule in a cardiac myocyte?

    <p>Propagation of electrical changes into the sarcoplasm</p> Signup and view all the answers

    How does the Transverse (T) tubule contribute to Excitation-Contraction Coupling in a cardiac myocyte?

    <p>By propagating electrical changes into the sarcoplasm</p> Signup and view all the answers

    What is the role of the dilated terminal of the sarcoplasmic reticulum in a cardiac myocyte?

    <p>Storage of calcium during muscle relaxation</p> Signup and view all the answers

    Where do 25% of intracellular Calcium ions enter from, in a cardiac myocyte?

    <p>T tubules through voltage gated Ca channels</p> Signup and view all the answers

    What distinguishes the sarcoplasmic reticulum in cardiac muscle from that in skeletal muscle?

    <p>Presence of T tubules and dyads</p> Signup and view all the answers

    How does the wide diameter of the T tubule impact calcium handling in a cardiac myocyte?

    <p>Increases influx of calcium ions from extracellular fluid</p> Signup and view all the answers

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