Physiology and Pathology of Heart Rate Regulation
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Questions and Answers

What is the amount of blood pumped out of each ventricle per beat called?

  • Stroke Volume (correct)
  • Cardiac Index
  • Cardiac Output
  • End Diastolic Volume

    • What is the correlation between resting cardiac output and body surface area?

  • Cardiac Index (correct)
  • Heart Rate
  • Stroke Volume
  • End Systolic Volume

    • What is the formula to calculate cardiac output?

  • Heart Rate x Cardiac Index
  • Stroke Volume x Heart Rate (correct)
  • End Diastolic Volume x End Systolic Volume
  • Cardiac Index x Body Surface Area

    • What is the normal End Diastolic Volume (EDV) of the ventricle?

    <p>120 ml</p> Signup and view all the answers

    What is the effect of an increase in End Systolic Volume (ESV) on Stroke Volume?

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

    What is the effect of an increase in venous return to the heart on Stroke Volume?

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

    Which of the following pathologies can affect Stroke Volume?

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

    What is the difference between the ventricular End Diastolic Volume and the End Systolic Volume?

    <p>Stroke Volume</p> Signup and view all the answers

    What happens to the plateau level of the cardiac output curve in marathon runners?

    <p>It increases by 60-100%</p> Signup and view all the answers

    What is the total effect of combining nervous excitation of the heart and hypertrophy in marathon runners on the heart's pumping ability?

    <p>The heart can pump as much as 30-40 L/min</p> Signup and view all the answers

    What is a factor that can cause hypoeffectivity of the heart?

    <p>Coronary artery blockage</p> Signup and view all the answers

    What is the result of increased arterial pressure against which the heart must pump?

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

    What can cause abnormal heart rhythm or rate of heartbeat?

    <p>Pathological factors</p> Signup and view all the answers

    What can be a result of coronary artery blockage?

    <p>Heart attack</p> Signup and view all the answers

    What is the effect of an increase in afterload on stroke volume?

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

    Which of the following factors decreases stroke volume?

    <p>Sitting or standing from lying position</p> Signup and view all the answers

    What is the effect of lowering aortic pressure on stroke volume?

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

    What are the three ways that the body regulates stroke volume from minute-to-minute?

    <p>Filling pressure, aortic pressure, and contractility</p> Signup and view all the answers

    What is the effect of changing filling pressure on stroke volume?

    <p>It changes stroke volume by changing LVEDV</p> Signup and view all the answers

    What is the effect of hemorrhage on stroke volume?

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

    Which of the following factors increases afterload?

    <p>High environmental temperature</p> Signup and view all the answers

    What is the effect of epinephrine on stroke volume?

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

    What is the frequency of ultrasonic waves emitted from a transducer/receiver in echocardiography?

    <p>2.25MHz</p> Signup and view all the answers

    What is reflected back from various parts of the heart in echocardiography?

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

    What does a recording of echoes displayed against time on an oscilloscope provide in echocardiography?

    <p>A record of the movements of the ventricular wall, septum and valves during the cardiac cycle</p> Signup and view all the answers

    What is an advantage of echocardiography?

    <p>Provides information about structure and movement of valves and chambers</p> Signup and view all the answers

    What is a disadvantage of echocardiography?

    <p>Less accurate and requires well-trained operator</p> Signup and view all the answers

    What is depicted in Figure 1.0?

    <p>Cardiac output curves for the normal heart and for hypoeffective and hypereffective hearts</p> Signup and view all the answers

    What is the right atrial pressure at point A on the normal cardiac output curve?

    <p>0 mmHg</p> Signup and view all the answers

    What is the cardiac output at point A on the normal cardiac output curve?

    <p>5 L/min</p> Signup and view all the answers

    What is the principle behind Fick's method?

    <p>The amount of a substance taken up by an organ is equal to the arterial level of the substance minus the venous level</p> Signup and view all the answers

    What is the advantage of the Direct Fick Method?

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

    What is the disadvantage of the Direct Fick Method?

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

    What is the purpose of the indicator dilution technique?

    <p>To measure cardiac output</p> Signup and view all the answers

    What is the advantage of the thermodilution technique?

    <p>The saline is completely innocuous</p> Signup and view all the answers

    What is the clinical usefulness of the Doppler technique and echocardiography?

    <p>Evaluating and planning therapy in patients with valvular lesions</p> Signup and view all the answers

    What is measured by the Doppler technique and echocardiography?

    <p>Velocity and volume of blood flow through valves</p> Signup and view all the answers

    What is the disadvantage of the indicator dilution technique?

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

    Study Notes

    Physiology Causes of Decreased Stroke Volume

    • During sleep, athletes may experience decreased stroke volume
    • Pathology causes include:
      • Heart failure
      • Congenital heart disease
      • Hypothyroidism
      • Hypothermia
      • Raised intracranial pressure
      • Certain drugs (antiarrhythmic, calcium channel blockers, beta blockers)

    Stroke Volume

    • Defined as the amount of blood pumped out of each ventricle per beat
    • Average stroke volume: 70 mL
    • Cardiac output: stroke volume x heart rate
    • Cardiac output (approximate): 5040 mL/min (70 mL x 72 beats/min)
    • Cardiac index: cardiac output per minute per square meter of body surface area
    • Average cardiac index: 3.2 L/min/m²

    Factors Affecting Stroke Volume

    • End-diastolic volume (EDV) and end-systolic volume (ESV) affect stroke volume
    • EDV: filled volume of ventricle prior to contraction (approx. 120 mL)
    • ESV: residual volume of blood remaining in ventricle after ejection (approx. 50 mL)
    • Stroke volume: EDV - ESV (approx. 70 mL)
    • Increase in EDV increases stroke volume, while increase in ESV decreases stroke volume
    • Strong heart contraction can decrease ESV to 10-20 mL, increasing stroke volume
    • Large amounts of blood flow into ventricles during diastole can increase EDV to 150-180 mL, increasing stroke volume

    Preload and Afterload

    • Preload affects stroke volume through increased venous return to the heart, increasing EDV
    • Increased EDV stretches muscle fibers, increasing force of ventricular contraction
    • Afterload affects stroke volume through pressure generated by the ventricle to eject blood into the aorta
    • Changes in afterload affect ESV and stroke volume
    • Increase in afterload increases ESV, decreases stroke volume

    Factors Affecting Cardiac Output

    • Anxiety and excitement: increase cardiac output by 50-100%
    • Eating: increase cardiac output by 30%
    • Exercise: increase cardiac output by up to 700%
    • High environmental temperature: increase cardiac output
    • Pregnancy: increase cardiac output
    • Epinephrine: increase cardiac output
    • Sitting or standing from lying position: decrease cardiac output by 20-30%
    • Rapid arrhythmias, heart disease: decrease cardiac output

    Pressure-Volume Loop

    • The body regulates stroke volume through three ways:
      • Filling pressure (preload)
      • Aortic pressure (afterload)
      • Contractility
    • Changing filling pressure changes stroke volume only by changing LVEDV (example: transfusion)
    • Lowering aortic pressure causes the ventricle to empty more completely, increasing stroke volume

    Methods of Measuring Cardiac Output

    • Direct Fick Method: accurate, but invasive (catheter insertion through patient's vein)
    • Indicator dilution technique: accurate, but invasive (injection of marker substance)
    • Thermodilution: accurate, non-invasive (saline injection through pulmonary artery)
    • Doppler technique + echocardiography: non-invasive, accurate, but requires well-trained operator

    Hyper- and Hypoeffective Heart

    • Hyper-effective heart: pumps better than normal, with increased cardiac output
    • Hypo-effective heart: pumps less than normal, with decreased cardiac output
    • Factors that cause hypoeffectivity include:
      • Coronary artery blockage
      • Inhibition of nervous excitation
      • Pathological factors affecting heart rhythm or rate
      • Valvular heart disease
      • Increased arterial pressure
      • Congenital heart disease
      • Myocarditis
      • Cardiac hypoxia

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    Heart Rate, Stroke Volume, and Cardiac Output PDF

    Description

    This quiz covers the physiological and pathological factors that affect heart rate regulation, including sleep, heart failure, and medications.

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