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

What determines the strength of contraction of each myocardial cell?

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

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

<p>Actin and myosin (C)</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 (B)</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 (B)</p> Signup and view all the answers

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

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

What happens to contractility when heart rate decreases?

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

Why can't cardiac muscle be tetanized?

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

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

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

What determines the strength of contraction of each myocardial cell?

<p>Intracellular free calcium concentration (B)</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 (A)</p> Signup and view all the answers

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

<p>Myosin and actin (C)</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 (B)</p> Signup and view all the answers

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

<p>Titin (D)</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 (D)</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 (B)</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 (D)</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 (B)</p> Signup and view all the answers

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

<p>Mitochondria (C)</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 (C)</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) (C)</p> Signup and view all the answers

Which term refers to the contractile strength of cardiac muscle?

<p>Ionotropy (D)</p> Signup and view all the answers

What is the primary mechanism for relaxation in cardiac muscle?

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

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

<p>Intracellular Ca2+ concentration (C)</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) (D)</p> Signup and view all the answers

What effect does parasympathetic stimulation have on cardiac contractility?

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

Which of the following mechanisms impacts contractility in cardiac muscle?

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

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

<p>Increasing intracellular Na+ (A)</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 (D)</p> Signup and view all the answers

What happens to contractility when heart rate increases?

<p>Contractility increases (B)</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 (C)</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 (C)</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 (A)</p> Signup and view all the answers

What determines the strength of contraction of each myocardial cell?

<p>Intracellular Ca2+ concentration (C)</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 (D)</p> Signup and view all the answers

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

<p>Titin (D)</p> Signup and view all the answers

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

<p>Fatty acid oxidation (A)</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 (A)</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 (B)</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 (B)</p> Signup and view all the answers

What happens to contractility when heart rate increases?

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

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

<p>Contractility increases (C)</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 (D)</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 (B)</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+ (C)</p> Signup and view all the answers

What happens to contractility when heart rate increases?

<p>Contractility increases (C)</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 (D)</p> Signup and view all the answers

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

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

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

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

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

<p>Troponin-C (A)</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 (B)</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 (D)</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 (D)</p> Signup and view all the answers

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

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

What is the primary mechanism for relaxation in cardiac muscle?

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

What determines the strength of contraction of each myocardial cell?

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

Which of the following mechanisms impacts contractility in cardiac muscle?

<p>Increasing heart rate (A)</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 (B)</p> Signup and view all the answers

What determines the strength of contraction of each myocardial cell?

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

What is the primary mechanism for relaxation in cardiac muscle?

<p>Decreased intracellular Ca2+ (B)</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 (C)</p> Signup and view all the answers

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

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

Why can't cardiac muscle be tetanized?

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

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

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

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