Muscle Contraction and Relaxation
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Questions and Answers

Which protein is involved in calcium-induced calcium release in cardiac muscle?

  • Troponin-C (correct)
  • Myosin
  • Actin
  • Tropomyosin

    • What is the role of the sodium-calcium exchanger in cardiac muscle?

  • To pump sodium ions out of the sarcoplasmic reticulum
  • To pump calcium ions out of the sarcoplasmic reticulum (correct)
  • To pump calcium ions into the sarcoplasmic reticulum
  • To pump sodium ions into the sarcoplasmic reticulum

    • What is the relationship between intracellular free calcium concentration and force generation by cardiac muscle?

  • Force generation is independent of intracellular free calcium concentration
  • As intracellular free calcium concentration increases, force generation increases (correct)
  • Intracellular free calcium concentration does not affect force generation
  • As intracellular free calcium concentration increases, force generation decreases

    • Which of the following is responsible for the strength of contraction of each myocardial cell?

    <p>Excitation-contraction coupling processes</p> Signup and view all the answers

    What is the main role of the T-tubular system in cardiac muscle?

    <p>Carry action potentials into the cell interior</p> Signup and view all the answers

    What is the function of the sarcoplasmic reticulum in excitation-contraction coupling?

    <p>Store and release Ca2+</p> Signup and view all the answers

    How does Ca2+ induce muscle contraction in cardiac muscle?

    <p>Ca2+ binds to troponin C, unblocking actin active sites</p> Signup and view all the answers

    Which of the following is NOT a mechanism that impacts contractility in the heart?

    <p>Decreasing extracellular Na+</p> Signup and view all the answers

    What is the effect of heart rate on contractility in the heart?

    <p>Increased heart rate increases contractility</p> Signup and view all the answers

    Can cardiac muscle be tetanized?

    <p>No, because the duration of the effective refractory period is approximately equal to the duration of the mechanical event</p> Signup and view all the answers

    How do defects in the sarcoplasmic reticulum Ca pump (SERCA) affect contractility in the heart?

    <p>They decrease contractility</p> Signup and view all the answers

    Which mechanism actively transports Ca2+ out of the cell by exchanging 3 Na+ for 1 Ca2+?

    <p>Na+-Ca2+ exchanger (NCX)</p> Signup and view all the answers

    Which mechanism actively transports Ca2+ back into the sarcoplasmic reticulum (SR) by using ATP?

    <p>ATP-dependent Ca2+-pump (SERCA)</p> Signup and view all the answers

    What is the term for the intrinsic ability of cardiac muscle to develop force at a given muscle length?

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

    Which mechanism increases the force of cardiac contractility by increasing the rate and magnitude of Ca2+ release from the sarcoplasmic reticulum (SR)?

    <p>Sympathetic stimulation of cardiac contractility</p> Signup and view all the answers

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