Podcast
Questions and Answers
What is the relationship described by Starling's Law regarding the heart's contraction?
What is the relationship described by Starling's Law regarding the heart's contraction?
How does sympathetic nerve stimulation affect myocardial contractility?
How does sympathetic nerve stimulation affect myocardial contractility?
What affects the difficulty of ejecting blood during ventricular contraction?
What affects the difficulty of ejecting blood during ventricular contraction?
What happens to stroke volume if arterial pressure falls?
What happens to stroke volume if arterial pressure falls?
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What role do baroreceptors play in heart rate control?
What role do baroreceptors play in heart rate control?
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How does a rise in venous pressure affect stroke volume?
How does a rise in venous pressure affect stroke volume?
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What mechanism is primarily responsible for cardiac output increase when arterial pressure falls?
What mechanism is primarily responsible for cardiac output increase when arterial pressure falls?
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What triggers the release of vasopressin in response to decreased systemic blood pressure?
What triggers the release of vasopressin in response to decreased systemic blood pressure?
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What is the relationship between total peripheral resistance (TPR) and arterial pressure when TPR falls and cardiac output remains unchanged?
What is the relationship between total peripheral resistance (TPR) and arterial pressure when TPR falls and cardiac output remains unchanged?
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What factors influence stroke volume?
What factors influence stroke volume?
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How does an increase in cardiac output (CO) affect arterial and venous pressure assuming TPR remains unchanged?
How does an increase in cardiac output (CO) affect arterial and venous pressure assuming TPR remains unchanged?
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What physiological response occurs when local vasodilators are released after eating a meal?
What physiological response occurs when local vasodilators are released after eating a meal?
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What best describes the relationship between venous pressure and ventricular filling?
What best describes the relationship between venous pressure and ventricular filling?
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What occurs in the heart during systole?
What occurs in the heart during systole?
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What happens to venous pressure when cardiac output decreases and TPR remains constant?
What happens to venous pressure when cardiac output decreases and TPR remains constant?
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Which factor is considered part of the control of cardiac output?
Which factor is considered part of the control of cardiac output?
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Flashcards
Stroke Volume
Stroke Volume
The volume of blood pumped out of the heart with each beat.
Afterload
Afterload
The pressure against which the heart must eject blood.
Preload
Preload
The amount of blood in the ventricle at the end of diastole, just before contraction.
Inotropic State
Inotropic State
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Total Peripheral Resistance (TPR)
Total Peripheral Resistance (TPR)
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Cardiac Output
Cardiac Output
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Systolic Pressure
Systolic Pressure
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Diastolic Pressure
Diastolic Pressure
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Starling's Law
Starling's Law
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End-Systolic Volume
End-Systolic Volume
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Aortic Impedance
Aortic Impedance
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Myocardial Contractility
Myocardial Contractility
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Autonomic Control of Heart Rate
Autonomic Control of Heart Rate
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Vasopressin
Vasopressin
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Compensatory Mechanisms
Compensatory Mechanisms
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Study Notes
Cardiac Output Overview
- Cardiac output is the product of stroke volume and heart rate.
- Arterial and venous pressures influence both.
Stroke Volume
- Determined by the interaction of preload, inotropic state, and afterload.
- Preload: the amount of blood in the ventricles before contraction.
- Inotropic state: the force of ventricular contraction.
- Afterload: the resistance the ventricles must overcome to eject blood.
- Stroke volume is the difference between end diastolic volume and end systolic volume.
- The heart fills in diastole.
Ventricular Filling
- Ventricles fill until intraventricular pressure equals venous pressure.
- Venous pressure directly affects ventricular filling.
- A relationship exists between venous pressure and ventricular volume, known as the ventricular compliance curve.
End Diastolic Volume and Force of Contraction
- Starling's Law of the heart: the more the heart fills, the harder it contracts. The stronger the contraction the larger the stroke volume.
- Rises in venous pressure automatically increase end diastolic volume.
Myocardial Contractility
- Myocardial contractility (inotropic state) is influenced by sympathetic and vagal nerve activity, drugs, and receptors.
- Sympathetic stimulation increases contractility.
- Vagal stimulation decreases contractility.
End Systolic Volume
- Determined by the force of ventricular contraction and the difficulty of ejecting blood (aortic impedance).
- Force of contraction is influenced by end diastolic volume (Starling's Law) and contractility.
- Contractility is increased by sympathetic stimulation.
- Aortic impedance, or the resistance to blood ejection from the ventricle, is largely determined by the TPR (total peripheral resistance).
Direct Effects of Arterial and Venous Pressures on Stroke Volume
- Increased venous pressure leads to increased stroke volume.
- Decreased arterial pressure leads to increased stroke volume.
Control of Heart Rate
- Heart rate is controlled by autonomic outflow to the heart, including baroreceptors, and signals from the carotid sinus.
- The carotid sinus senses arterial pressure.
- Signals are sent to the medulla to regulate the heart.
- Falls in arterial pressure increase heart rate by reducing parasympathetic activity and increasing sympathetic activity.
- Increases in heart rate increase contractility via increasing sympathetic activity.
Total Peripheral Resistance (TPR) Changes
- TPR affects both arterial and venous pressure.
- If TPR falls and cardiac output remains constant, arterial pressure falls, and venous pressure rises.
- If TPR rises and cardiac output remains constant, arterial pressure rises, and venous pressure falls.
Changes in Demand for Blood
- Total peripheral resistance (TPR) is inversely proportional to the body's need for blood.
- Metabolic changes affect TPR and generate signals in the form of changes in arterial and venous pressure.
- For example, eating a meal increases blood flow to the gut. This is signaled by local vasodilators and leads to decreased TPR.
Demand-Led Pumping
- If the body needs more blood, the heart needs to pump more to meet the 'demand'.
- Demand is expressed as changes in arterial and venous pressures.
- The heart responds to these changes (falls in arterial pressure and rises in venous pressure) by increasing its pumping action.
Control of Cardiac Output Summary
- Cardiac output is influenced by stroke volume (preload, inotropic state, afterload), and heart rate.
- Both arterial and venous pressure affect these parameters, and in turn cardiac output.
Compensatory Mechanisms of Blood Pressure
- Decreased systemic blood pressure stimulates central baroreceptors
- This triggers the release of vasopressin from the pituitary gland to increase peripheral vascular resistance (vasoconstriction) to increase blood pressure.
Summary
- Falls in arterial pressure increase cardiac output via increased stroke volume and heart rate.
- Rises in venous pressure lead to increased heart rate and increased stroke volume.
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Description
This quiz explores the key concepts surrounding cardiac output, including its definition and components such as stroke volume and heart rate. It delves into the physiological factors influencing stroke volume and examines the principles of ventricular filling, compliance, and Starling's Law. Test your understanding of these critical cardiovascular principles.
