Questions and Answers
What is cardiac output?
Volume of blood ejected by each ventricle each minute.
What is cardiac output determined by?
What is stroke volume?
Blood pumped per beat.
What is stroke volume determined by?
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What is the Frank-Starling law of the heart?
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What influences venous return?
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What is afterload?
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What does the sympathetic nervous system do to stroke volume?
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How is heart rate determined?
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What is ejection fraction of cardiac output?
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What does the cardiovascular system consist of?
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How is the flow of blood measured?
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What are the determinants of resistance in blood flow?
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What is the relationship between vessel's radius and blood flow?
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What function do arteries serve?
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What is blood pressure?
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What is systolic pressure?
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What is diastolic pressure?
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What is pulse pressure?
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What is Mean Arterial Pressure (MAP)?
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What determines MAP?
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What type of muscle is found in arterioles?
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What do arterioles determine?
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What alters the radius of vessels?
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What is the only steady blood flow?
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Study Notes
Cardiac Output
- Volume of blood ejected by each ventricle per minute.
- Determined by heart rate (HR) and stroke volume (SV). Equation: CO = HR x SV.
Stroke Volume
- Amount of blood pumped per heartbeat, measured in ml/beat.
- Influenced by:
- End diastolic volume (EDV): blood volume in ventricles before contraction, indicating venous return.
- Afterload: resistance the heart must overcome to eject blood.
- Sympathetic activity: enhances stroke volume.
Frank-Starling Law
- The heart pumps according to the amount of blood received; increased diastolic volume leads to increased stroke volume.
Venous Return
- Easier when lying down than standing due to gravity effects.
- Higher venous return when lying down, indicating blood accumulation in the upper body.
Cardiac Muscle
- Not at optimal resting length at rest; the muscle stretches as it fills with blood.
Afterload Impact
- Increased afterload decreases stroke volume; smaller vessel diameter requires more work from the heart.
Sympathetic Nervous System
- Increases stroke volume through enhanced contractility; increases calcium in the sarcoplasmic reticulum, enhancing ventricular contraction strength.
Heart Rate Determinants
- Influenced by the balance of sympathetic (increases HR) and parasympathetic (decreases HR) activity on the sinoatrial (SA) node.
- Parasympathetic tone dominates at rest, slowing the intrinsic heart rate.
Ejection Fraction
- Fraction of blood pumped out of the heart with each beat, calculated as SV/EDV x 100.
- Normal ejection fraction ranges from 50% to 65%.
Components of Cardiovascular System
- Comprised of heart, blood, and blood vessels which transport blood.
Blood Flow Measurement
- Flow rate (F) determined by the pressure gradient (P) and resistance (R) in vessels: F = P/R.
- Blood flow is directly proportional to pressure and inversely related to resistance.
Determinants of Resistance
- Blood viscosity, vessel length (increases with obesity), and vessel radius (the main determinant).
Vessel Radius Impact
- Minor alterations in vessel radius can significantly affect blood flow; resistance is proportional to 1/radius^4.
Arteries
- Elastic and allow low-resistance blood flow due to large radius; function as a pressure reservoir during heart relaxation.
Blood Pressure
- Force of blood against vessel walls, influenced by blood volume and vessel wall compliance (stretchability).
Systolic and Diastolic Pressure
- Systolic: maximum arterial pressure; average is approximately 120 mmHg.
- Diastolic: minimum pressure; average is approximately 80 mmHg.
Pulse Pressure
- Difference between systolic and diastolic pressures.
Mean Arterial Pressure (MAP)
- Average pressure pushing blood into tissues throughout the cardiac cycle, calculated as diastolic + 1/3(systolic - diastolic) or CO x total peripheral resistance.
MAP Determinant
- Primarily determined by arterioles.
Muscle Type in Arterioles
- Composed of smooth muscle.
Arterioles Function
- Control the radius of blood vessels through:
- Vasoconstriction: narrowing blood vessels.
- Vasodilation: widening blood vessels.
Radius Alterations in Vessels
- Influenced by changes in other organs affecting localized blood flow.
Consistent Blood Flow
- Steady blood flow is maintained primarily to the brain.
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Description
Test your knowledge on cardiac output and stroke volume concepts with these flashcards. Learn the definitions, formulas, and determinants involved in understanding how blood is ejected from the heart. Perfect for students studying physiology or related medical fields.
