Cardiac Muscle Physiology
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Questions and Answers

What is the primary factor that modulates the contraction of cardiac muscles?

  • K+ ions
  • Na+ ions
  • Mg2+ ions
  • Ca2+ ions (correct)

    • What is the term for the force of contraction of cardiac muscles?

  • Lusitropy
  • Dromotropy
  • Chronotropy
  • Inotropy (correct)

    • What is the effect of a negative inotropic effect?

  • The force of contraction increases
  • The force of contraction decreases (correct)
  • The heart rate increases
  • The heart rate decreases

    • What is the term for the property of cardiac muscle relaxation?

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

    What is the effect of a positive lusitropic effect?

    <p>The rate of myocardial relaxation increases</p> Signup and view all the answers

    What is the term for the heart rate?

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

    What is the effect of a positive chronotropic effect?

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

    What binds to Beta 1 (β1) receptors in the heart?

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

    What happens to the left ventricular volume during the isovolumic contraction phase?

    <p>It remains the same</p> Signup and view all the answers

    What is the result of the rise in pressure during the isovolumic contraction phase?

    <p>Opening of the aortic valve</p> Signup and view all the answers

    What happens to the aortic flow during the rapid ejection phase?

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

    What happens to the left ventricular volume during the rapid ejection phase?

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

    What is the duration of diastole compared to systole under normal conditions?

    <p>It is longer</p> Signup and view all the answers

    What is the atrio-ventricular pressure difference needed to open the mitral valve?

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

    What happens to the left ventricular pressure at the beginning of the diastole?

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

    What happens to the left ventricular volume during the diastole?

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

    What is the relationship between heart rate and stroke volume at a normal cardiac output?

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

    What is cardiac output determined by?

    <p>Heart rate and stroke volume</p> Signup and view all the answers

    What happens to stroke volume when heart rate increases?

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

    What is the effect of high aortic valve pressure on blood ejection?

    <p>It makes blood ejection more difficult</p> Signup and view all the answers

    What determines wall stress in the ventricle?

    <p>Law of Laplace</p> Signup and view all the answers

    What happens to the ventricular muscle when there is an increase in arterial pressure and/or wall stress?

    <p>It must exert greater force</p> Signup and view all the answers

    In what condition does wall stress have a significant effect on afterload?

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

    What is the formula for cardiac output?

    <p>CO = HR x SV</p> Signup and view all the answers

    What is the effect of increased sympathetic activation on heart rate?

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

    What percentage of Ca2+ is reuptaken by SERCA in sarcoplasm?

    <p>80%</p> Signup and view all the answers

    What is the volume of blood in the left ventricle before systole?

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

    What is the function of the Na-Ca exchanger in cardiac muscle cells?

    <p>Transports Ca2+ from inside to outside in exchange with Na+</p> Signup and view all the answers

    What is the formula to calculate cardiac output?

    <p>HR x SV</p> Signup and view all the answers

    Which event in the cardiac cycle corresponds to Phase 2?

    <p>Isovolumetric Ventricular Contraction</p> Signup and view all the answers

    What is the effect of endurance training on heart rate?

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

    What is the percentage of blood pumped out of the left ventricle in each contraction?

    <p>67%</p> Signup and view all the answers

    What is the characteristic of the PV curve during diastole?

    <p>Flat/less steep curve</p> Signup and view all the answers

    What happens to the ventricles during diastole?

    <p>They become less distensible</p> Signup and view all the answers

    What is the stroke volume if the EDV is 150 mL and ESV is 50 mL?

    <p>100 mL</p> Signup and view all the answers

    What is the result of a large increase in volume during diastole?

    <p>Low pressure change</p> Signup and view all the answers

    What is the cardiac output if the heart rate is 55 bpm and stroke volume is 100 mL?

    <p>5500 mL/min</p> Signup and view all the answers

    What is the volume of blood left in the left ventricle after systole?

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

    What is the function of Ca2+-ATPase in cardiac muscle cells?

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

    What is the characteristic of the PV curve during systole?

    <p>Steep curve</p> Signup and view all the answers

    What is the result of a small increase in volume during systole?

    <p>High pressure change</p> Signup and view all the answers

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