Molecular Events in Muscle Contraction Quiz
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Questions and Answers

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

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

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

  • To pump calcium into the cell
  • To pump sodium out of the cell
  • To pump sodium into the cell
  • To pump calcium out of the cell (correct)

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

  • Calcium concentration has no effect on force generation
  • As calcium concentration increases, force generation decreases
  • As calcium concentration increases, force generation increases (correct)
  • There is no relationship between calcium concentration and force generation

    • Which factors influence the performance of the heart's contraction?

    <p>All of the above</p> Signup and view all the answers

    What determines the strength of contraction of each myocardial cell?

    <p>Both A and B</p> Signup and view all the answers

    What are the contractile elements responsible for active tension in the myocardial cell?

    <p>Actin and myosin</p> Signup and view all the answers

    What is the role of the T-tubular system in excitation-contraction coupling?

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

    Which of the following is true about the effect of ACh on Ca2+ current during the plateau of the action potential?

    <p>ACh decreases inward Ca2+ current</p> Signup and view all the answers

    What is the effect of increasing intracellular Na+ on contractility?

    <p>Increases contractility</p> Signup and view all the answers

    What happens to contractility when heart rate decreases?

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

    Why can't cardiac muscle be tetanized?

    <p>The effective refractory period is too short</p> Signup and view all the answers

    Which of the following is NOT a mechanism for relaxation in cardiac muscle?

    <p>Passive diffusion of Ca2+ out of the cell</p> Signup and view all the answers

    Which term refers to the intrinsic ability of cardiac muscle to develop force at a given muscle length?

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

    What is the primary factor that determines the amount of Ca2+ released from the sarcoplasmic reticulum during excitation-contraction coupling?

    <p>The amount of Ca2+ previously stored in the SR</p> Signup and view all the answers

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

    <p>Phosphorylation of TnI</p> Signup and view all the answers

    Which protein plays a role in calcium-induced calcium release in cardiac muscle?

    <p>Troponin-C</p> Signup and view all the answers

    What is the primary factor that determines the amount of calcium released from the sarcoplasmic reticulum during excitation-contraction coupling?

    <p>Troponin-C</p> Signup and view all the answers

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

    <p>To pump calcium out of the cell</p> Signup and view all the answers

    What determines the strength of contraction of each myocardial cell?

    <p>Intracellular free calcium concentration</p> Signup and view all the answers

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

    <p>Direct relationship</p> Signup and view all the answers

    What are the contractile elements responsible for active tension in the myocardial cell?

    <p>Myosin and actin</p> Signup and view all the answers

    Which of the following is NOT a mechanism for relaxation in cardiac muscle?

    <p>Ca2+ release from the sarcoplasmic reticulum</p> Signup and view all the answers

    Which of the following is responsible for passive tension in the myocardial cell?

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

    What is the function of the transverse-tubular (T-tubular) system in cardiac muscle?

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

    Which of the following is true about the sliding filament mechanism in the myocardial cell?

    <p>Shortening occurs by the sliding of thick and thin filaments past each other</p> Signup and view all the answers

    What is the role of troponin C in cardiac muscle contraction?

    <p>It binds to calcium ions, inducing a conformational change</p> Signup and view all the answers

    Which of the following is NOT a characteristic of the myocardial cell?

    <p>Has a poorly developed T-tubular system in the ventricles</p> Signup and view all the answers

    What is the main source of ATP production in cardiac muscle?

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

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

    <p>Remove calcium ions from the myoplasm to promote relaxation</p> Signup and view all the answers

    Which of the following agents actively transports Ca2+ out of the cell when [Ca2+] is high?

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

    Which term refers to the contractile strength of cardiac muscle?

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

    What is the primary mechanism for relaxation in cardiac muscle?

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

    What factor determines the strength of contraction of each myocardial cell?

    <p>Intracellular Ca2+ concentration</p> Signup and view all the answers

    Which protein is phosphorylated to stimulate the activity of the SERCA pump in cardiac muscle?

    <p>Phospholamban (PLB)</p> Signup and view all the answers

    What effect does parasympathetic stimulation have on cardiac contractility?

    <p>Decreases contractility</p> Signup and view all the answers

    What is the main role of the sodium-calcium exchanger (NCX) in cardiac muscle?

    <p>Transporting Na+ out of the cell</p> Signup and view all the answers

    Which of the following mechanisms impacts contractility in cardiac muscle?

    <p>Increasing intracellular Na+</p> Signup and view all the answers

    Which of the following is NOT a mechanism for relaxation in cardiac muscle?

    <p>Increasing intracellular Na+</p> Signup and view all the answers

    What is the effect of decreasing the Na+ gradient across the sarcolemma on contractility?

    <p>Positive inotropic effect</p> Signup and view all the answers

    What happens to contractility when heart rate increases?

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

    Which of the following is true about the effect of ACh on Ca2+ current during the plateau of the action potential?

    <p>ACh decreases inward Ca2+ current</p> Signup and view all the answers

    What is the primary factor that determines the amount of Ca2+ released from the sarcoplasmic reticulum during excitation-contraction coupling?

    <p>Intracellular Ca2+ concentration</p> Signup and view all the answers

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

    <p>To decrease intracellular Ca2+ concentration</p> Signup and view all the answers

    What determines the strength of contraction of each myocardial cell?

    <p>Intracellular Ca2+ concentration</p> Signup and view all the answers

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

    <p>Directly proportional</p> Signup and view all the answers

    Which of the following is responsible for the passive tension in the myocardial cell?

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

    What is the main source of ATP production in cardiac muscle?

    <p>Fatty acid oxidation</p> Signup and view all the answers

    What is the role of the sodium-calcium exchanger (NCX) in cardiac muscle?

    <p>Transporting sodium out of the cell and calcium into the cell</p> Signup and view all the answers

    What determines the strength of contraction of each myocardial cell?

    <p>The strength of contraction of all the individual myocardial cells</p> Signup and view all the answers

    What is the primary factor that determines the amount of calcium released from the sarcoplasmic reticulum during excitation-contraction coupling?

    <p>The concentration of calcium in the cytoplasm</p> Signup and view all the answers

    What happens to contractility when heart rate increases?

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

    What is the effect of increasing intracellular Na+ on contractility?

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

    Which of the following is NOT a mechanism for relaxation in cardiac muscle?

    <p>Active transport of Ca2+ into the cell by the Na+-Ca2+ exchanger</p> Signup and view all the answers

    What is the primary mechanism for relaxation in cardiac muscle?

    <p>Active transport of Ca2+ out of the cell by the Na+-Ca2+ exchanger</p> Signup and view all the answers

    What is the main role of the sodium-calcium exchanger (NCX) in cardiac muscle?

    <p>To transport Ca2+ into the cell in exchange for Na+</p> Signup and view all the answers

    What happens to contractility when heart rate increases?

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

    What determines the strength of contraction of each myocardial cell?

    <p>The amount of Ca2+ released from the sarcoplasmic reticulum</p> Signup and view all the answers

    What is the effect of increasing intracellular Na+ on contractility?

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

    Which of the following is responsible for passive tension in the myocardial cell?

    <p>The extracellular matrix</p> Signup and view all the answers

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

    <p>Troponin-C</p> Signup and view all the answers

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

    <p>To pump sodium out of the cell and calcium into the cell</p> Signup and view all the answers

    What is the primary factor that determines the amount of calcium released from the sarcoplasmic reticulum during excitation-contraction coupling?

    <p>Calcium-induced calcium release</p> Signup and view all the answers

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

    <p>To pump sodium out of the cell and calcium into the cell</p> Signup and view all the answers

    What is the effect of increasing intracellular Na+ on contractility?

    <p>It increases contractility</p> Signup and view all the answers

    What is the primary mechanism for relaxation in cardiac muscle?

    <p>Sarcoplasmic reticulum Ca2+ pump</p> Signup and view all the answers

    What determines the strength of contraction of each myocardial cell?

    <p>Calcium concentration</p> Signup and view all the answers

    Which of the following mechanisms impacts contractility in cardiac muscle?

    <p>Increasing heart rate</p> Signup and view all the answers

    Which of the following is true about the effect of ACh on Ca2+ current during the plateau of the action potential?

    <p>ACh decreases inward Ca2+ current</p> Signup and view all the answers

    What determines the strength of contraction of each myocardial cell?

    <p>Intracellular Ca2+ concentration</p> Signup and view all the answers

    What is the primary mechanism for relaxation in cardiac muscle?

    <p>Decreased intracellular Ca2+</p> Signup and view all the answers

    What is the main role of the sodium-calcium exchanger (NCX) in cardiac muscle?

    <p>Transporting Ca2+ out of the cell and Na+ into the cell</p> Signup and view all the answers

    What is the effect of increasing intracellular Na+ on contractility?

    <p>Increases contractility</p> Signup and view all the answers

    Why can't cardiac muscle be tetanized?

    <p>Due to the duration of the effective refractory period</p> Signup and view all the answers

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

    <p>Directly proportional</p> Signup and view all the answers

    What is the main source of ATP production in cardiac muscle?

    <p>Fatty acid oxidation</p> Signup and view all the answers

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