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Questions and Answers
What is the amount of blood pumped out of each ventricle per beat called?
What is the amount of blood pumped out of each ventricle per beat called?
What is the correlation between resting cardiac output and body surface area?
What is the correlation between resting cardiac output and body surface area?
What is the formula to calculate cardiac output?
What is the formula to calculate cardiac output?
What is the normal End Diastolic Volume (EDV) of the ventricle?
What is the normal End Diastolic Volume (EDV) of the ventricle?
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What is the effect of an increase in End Systolic Volume (ESV) on Stroke Volume?
What is the effect of an increase in End Systolic Volume (ESV) on Stroke Volume?
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What is the effect of an increase in venous return to the heart on Stroke Volume?
What is the effect of an increase in venous return to the heart on Stroke Volume?
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Which of the following pathologies can affect Stroke Volume?
Which of the following pathologies can affect Stroke Volume?
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What is the difference between the ventricular End Diastolic Volume and the End Systolic Volume?
What is the difference between the ventricular End Diastolic Volume and the End Systolic Volume?
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What happens to the plateau level of the cardiac output curve in marathon runners?
What happens to the plateau level of the cardiac output curve in marathon runners?
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What is the total effect of combining nervous excitation of the heart and hypertrophy in marathon runners on the heart's pumping ability?
What is the total effect of combining nervous excitation of the heart and hypertrophy in marathon runners on the heart's pumping ability?
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What is a factor that can cause hypoeffectivity of the heart?
What is a factor that can cause hypoeffectivity of the heart?
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What is the result of increased arterial pressure against which the heart must pump?
What is the result of increased arterial pressure against which the heart must pump?
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What can cause abnormal heart rhythm or rate of heartbeat?
What can cause abnormal heart rhythm or rate of heartbeat?
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What can be a result of coronary artery blockage?
What can be a result of coronary artery blockage?
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What is the effect of an increase in afterload on stroke volume?
What is the effect of an increase in afterload on stroke volume?
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Which of the following factors decreases stroke volume?
Which of the following factors decreases stroke volume?
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What is the effect of lowering aortic pressure on stroke volume?
What is the effect of lowering aortic pressure on stroke volume?
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What are the three ways that the body regulates stroke volume from minute-to-minute?
What are the three ways that the body regulates stroke volume from minute-to-minute?
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What is the effect of changing filling pressure on stroke volume?
What is the effect of changing filling pressure on stroke volume?
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What is the effect of hemorrhage on stroke volume?
What is the effect of hemorrhage on stroke volume?
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Which of the following factors increases afterload?
Which of the following factors increases afterload?
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What is the effect of epinephrine on stroke volume?
What is the effect of epinephrine on stroke volume?
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What is the frequency of ultrasonic waves emitted from a transducer/receiver in echocardiography?
What is the frequency of ultrasonic waves emitted from a transducer/receiver in echocardiography?
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What is reflected back from various parts of the heart in echocardiography?
What is reflected back from various parts of the heart in echocardiography?
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What does a recording of echoes displayed against time on an oscilloscope provide in echocardiography?
What does a recording of echoes displayed against time on an oscilloscope provide in echocardiography?
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What is an advantage of echocardiography?
What is an advantage of echocardiography?
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What is a disadvantage of echocardiography?
What is a disadvantage of echocardiography?
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What is depicted in Figure 1.0?
What is depicted in Figure 1.0?
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What is the right atrial pressure at point A on the normal cardiac output curve?
What is the right atrial pressure at point A on the normal cardiac output curve?
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What is the cardiac output at point A on the normal cardiac output curve?
What is the cardiac output at point A on the normal cardiac output curve?
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What is the principle behind Fick's method?
What is the principle behind Fick's method?
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What is the advantage of the Direct Fick Method?
What is the advantage of the Direct Fick Method?
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What is the disadvantage of the Direct Fick Method?
What is the disadvantage of the Direct Fick Method?
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What is the purpose of the indicator dilution technique?
What is the purpose of the indicator dilution technique?
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What is the advantage of the thermodilution technique?
What is the advantage of the thermodilution technique?
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What is the clinical usefulness of the Doppler technique and echocardiography?
What is the clinical usefulness of the Doppler technique and echocardiography?
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What is measured by the Doppler technique and echocardiography?
What is measured by the Doppler technique and echocardiography?
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What is the disadvantage of the indicator dilution technique?
What is the disadvantage of the indicator dilution technique?
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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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Description
This quiz covers the physiological and pathological factors that affect heart rate regulation, including sleep, heart failure, and medications.