Cardiac Muscle Contraction: Sarcomere Steps
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Questions and Answers

What are the three variables that may influence stroke volume?

  • Venous return, presence of inotropic agents, and afterload (correct)
  • End-diastolic volume, end-systolic volume, and preload
  • Venous return, presence of inotropic agents, and preload
  • Venous return, end-diastolic volume, and end-systolic volume

    • What is the typical end-diastolic volume (EDV) in a resting adult?

  • 150 mL
  • 130 mL (correct)
  • 60 mL
  • 100 mL

    • What is the typical end-systolic volume (ESV) in a resting adult?

  • 30 mL
  • 75 mL
  • 45 mL
  • 60 mL (correct)

    • What is the formula for calculating stroke volume?

    <p>SV = EDV - ESV (C)</p> Signup and view all the answers

    Which of the following is NOT a factor that influences end-diastolic volume (EDV)?

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

    How does end-systolic volume (ESV) affect stroke volume?

    <p>Decreasing ESV increases stroke volume (C)</p> Signup and view all the answers

    What initiates cardiac muscle contraction?

    <p>Binding of calcium ions to troponin (A)</p> Signup and view all the answers

    What is the role of ATP in cardiac muscle contraction?

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

    What is the role of the sarcoplasmic reticulum in cardiac muscle relaxation?

    <p>To reuptake calcium ions from the sarcoplasm (B)</p> Signup and view all the answers

    What happens during the powerstroke in cardiac muscle contraction?

    <p>The myosin head swivels, pulling the thin filament (C)</p> Signup and view all the answers

    What is the role of plasma membrane calcium pumps in cardiac muscle relaxation?

    <p>To remove calcium ions from the cardiac muscle cell (A)</p> Signup and view all the answers

    What happens to the sarcomeres during cardiac muscle relaxation?

    <p>They return to their resting length (C)</p> Signup and view all the answers

    Which of the following statements is true about ventricular balance?

    <p>Both ventricles pump equal amounts of blood. (B)</p> Signup and view all the answers

    Why is the left ventricle larger and stronger than the right ventricle?

    <p>To pump the same amount of blood through the longer systemic circulation. (D)</p> Signup and view all the answers

    What condition can result from sustained pumping of unequal amounts of blood by the ventricles?

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

    What is the analogy used to explain the difference in work required by the left and right ventricles?

    <p>Throwing a baseball two different distances (D)</p> Signup and view all the answers

    Which of the following is true about the pressure within the left atrium, left ventricle, and aorta during the cardiac cycle?

    <p>The pressure changes in these chambers are shown in Figure 19.24. (C)</p> Signup and view all the answers

    What information is provided in Figure 19.24?

    <p>All of the above. (D)</p> Signup and view all the answers

    What happens to the overlap of thick and thin filaments in cardiac muscle cells during a more forceful ventricular contraction?

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

    How does a decrease in venous return affect the formation of crossbridges in cardiac muscle cells?

    <p>Decreases the formation of crossbridges (D)</p> Signup and view all the answers

    What causes venous return to increase according to the text?

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

    How does a decrease in venous return affect ventricular contraction strength?

    <p>Decreases ventricular contraction strength (A)</p> Signup and view all the answers

    What analogy is provided in the text to explain venous return?

    <p>Filling a balloon with water (D)</p> Signup and view all the answers

    Why does venous return increase during exercise according to the text?

    <p>Higher venous pressure (C)</p> Signup and view all the answers

    What causes the semilunar valves to close during the cardiac cycle?

    <p>The pressure within the ventricles is greater than the pressure within the arterial trunks. (C)</p> Signup and view all the answers

    Why do the AV valves remain closed during the phase when the semilunar valves are closed?

    <p>The pressure within the ventricles is still greater than the pressure within the atria. (A)</p> Signup and view all the answers

    What happens to the blood volume within the ventricular chambers during the phase when all heart valves are closed?

    <p>The blood volume remains the same. (A)</p> Signup and view all the answers

    What causes the AV valves to open during the cardiac cycle?

    <p>The pressure within the ventricles decreases below the pressure within the atria. (B)</p> Signup and view all the answers

    What is the purpose of the opening of the AV valves during the cardiac cycle?

    <p>To allow blood to flow from the atria into the ventricles for ventricular filling. (B)</p> Signup and view all the answers

    What is the significance of the cardiac cycle being repeated with each heartbeat?

    <p>It ensures a consistent flow of blood throughout the body. (A)</p> Signup and view all the answers

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