Pharmacology Cardiac Hemodynamics Overview and Components
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Questions and Answers

What are the two primary functions of the circulatory system?

  • Fight infection and regulate temperature
  • Delivery of oxygen, nutrients, hormones, and removal of carbon dioxide and metabolic wastes (correct)
  • Transport of blood and collection of wastes
  • Delivery of oxygen and removal of hormones

    • Which component of the circulatory system is responsible for regulating local blood flow?

  • Capillaries
  • Arteries
  • Veins
  • Arterioles (correct)

    • How does the distensibility of veins compare to arteries?

  • Veins are less distensible than arteries
  • Veins have no distensibility
  • Veins are equally distensible as arteries
  • Veins are 6 to 10 times more distensible than arteries (correct)

    • What percentage of blood is typically found in the systemic circulation of an adult?

    <p>84%</p> Signup and view all the answers

    What is the pumping organ in the circulatory system?

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

    Which part of the circulatory system is responsible for the exchange of gases and nutrients?

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

    What term is used to describe the systemic circulation?

    <p>Greater circulation</p> Signup and view all the answers

    Which vessel type serves as a major reservoir for blood?

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

    What is the primary mechanism through which angiotensin II influences blood pressure?

    <p>Causes vasoconstriction</p> Signup and view all the answers

    How does water retention by the kidneys affect arterial pressure (AP)?

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

    What effect does postural hypotension have on cardiac output when transitioning to an upright position?

    <p>Decreases due to blood pooling</p> Signup and view all the answers

    Which mechanism primarily helps to prevent postural hypotension in healthy individuals?

    <p>Auxiliary venous pumps</p> Signup and view all the answers

    What is a key action of the natriuretic peptides in response to volume overload?

    <p>Lowers blood volume</p> Signup and view all the answers

    Which hormone is primarily responsible for water retention in response to low arterial pressure?

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

    What physiological change occurs when blood volume becomes excessive?

    <p>Increased release of ANP and BNP</p> Signup and view all the answers

    What immediate effect does the baroreceptor reflex have in response to a drop in arterial pressure?

    <p>Increases heart rate and constricts blood vessels</p> Signup and view all the answers

    Which of the following is a primary action of C-natriuretic peptide (CNP)?

    <p>Induces vasodilation</p> Signup and view all the answers

    What condition results from a drug that prevents venoconstriction?

    <p>Intensified postural hypotension</p> Signup and view all the answers

    What role do natriuretic peptides play during heart failure?

    <p>Suppressing RAAS</p> Signup and view all the answers

    When arterial pressure is chronically low, how do kidneys respond?

    <p>Retain fluid</p> Signup and view all the answers

    What primarily causes renal blood flow reduction during low arterial pressure events?

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

    Which condition is characterized by pooling of blood in the veins resulting from standing up quickly?

    <p>Postural hypotension</p> Signup and view all the answers

    What is the primary determinant of resistance to blood flow in the circulatory system?

    <p>Vessel diameter</p> Signup and view all the answers

    Which mechanism most significantly assists venous return to the heart?

    <p>Contraction of skeletal muscles</p> Signup and view all the answers

    How does vessel constriction affect blood flow?

    <p>Decreases blood flow by increasing resistance</p> Signup and view all the answers

    What does cardiac output (CO) depend on?

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

    What role does preload play in stroke volume?

    <p>Increased preload raises stroke volume</p> Signup and view all the answers

    Which statement is true regarding afterload?

    <p>Afterload is the arterial pressure the left ventricle must overcome</p> Signup and view all the answers

    What primarily regulates heart rate?

    <p>Autonomic nervous system</p> Signup and view all the answers

    What is the relationship described by the Starling law of the heart?

    <p>Increased muscle fiber length increases contractile force</p> Signup and view all the answers

    When blood pressure drops, what must happen to maintain adequate blood flow?

    <p>Cardiac output must increase</p> Signup and view all the answers

    Which statement regarding stroke volume is false?

    <p>Stroke volume is unaffected by afterload</p> Signup and view all the answers

    How does venous wall constriction affect venous pressure?

    <p>Increases venous pressure</p> Signup and view all the answers

    What percentage of blood is found in the venous system in systemic circulation?

    <p>64%</p> Signup and view all the answers

    What initiates the heart's electrical impulse to increase heart rate?

    <p>Sympathetic nervous system acting on SA node</p> Signup and view all the answers

    Which description of blood flow is correct?

    <p>Blood flow is driven by pressure gradients</p> Signup and view all the answers

    What is the primary determinant of stroke volume (SV)?

    <p>Venous return</p> Signup and view all the answers

    Which of the following factors can raise systemic filling pressure?

    <p>Constricting veins</p> Signup and view all the answers

    How does the Starling law affect the output of the right and left ventricles?

    <p>Increased filling of one ventricle affects the other</p> Signup and view all the answers

    What role does the autonomic nervous system (ANS) play in regulating arterial pressure (AP)?

    <p>It adjusts cardiac output and peripheral resistance</p> Signup and view all the answers

    Which factor impedes venous return when elevated?

    <p>Right atrial pressure</p> Signup and view all the answers

    What does the baroreceptor reflex primarily respond to?

    <p>Rapid changes in arterial pressure</p> Signup and view all the answers

    Which system is responsible for long-term control of arterial pressure?

    <p>Renin-angiotensin-aldosterone system (RAAS)</p> Signup and view all the answers

    What is the effect of sympathetic tone on the heart?

    <p>Increases heart rate and contractility</p> Signup and view all the answers

    What happens to the baroreceptor reflex when arterial pressure remains elevated for an extended period?

    <p>It resets to the new elevated pressure</p> Signup and view all the answers

    Which of the following increases arterial pressure (AP)?

    <p>Increased peripheral resistance</p> Signup and view all the answers

    What happens during acute changes in blood pressure as sensed by baroreceptors?

    <p>They trigger immediate actions to restore pressure</p> Signup and view all the answers

    How is arterial pressure defined mathematically?

    <p>$AP = CO imes PR$</p> Signup and view all the answers

    What condition can lead to a failing heart according to Starling law principles?

    <p>Increased blood volume with ineffective contraction</p> Signup and view all the answers

    What is the primary function of the pulmonary circulation?

    <p>Deliver blood to the lungs for oxygenation</p> Signup and view all the answers

    How do arteries and veins differ in terms of their physical structure?

    <p>Arteries do not stretch easily under pressure</p> Signup and view all the answers

    What percentage of blood in an adult is typically found in the heart?

    <p>7%</p> Signup and view all the answers

    What is the function of capillaries in the circulatory system?

    <p>Site for the exchange of fluids and gases</p> Signup and view all the answers

    What role do venules play in the circulatory system?

    <p>Collect blood from capillaries</p> Signup and view all the answers

    In terms of blood distribution, where is the majority of blood located in an adult?

    <p>In the systemic circulation</p> Signup and view all the answers

    Which statement regarding hemodynamics is true?

    <p>It includes regulatory mechanisms related to pharmacology</p> Signup and view all the answers

    What occurs to veins in response to small increases in venous pressure?

    <p>They increase in diameter significantly</p> Signup and view all the answers

    What primarily determines resistance to blood flow within the vessels?

    <p>Vessel diameter, length, and blood viscosity</p> Signup and view all the answers

    Which mechanism most effectively aids venous return to the heart?

    <p>Valves in veins preventing backflow</p> Signup and view all the answers

    What factors primarily regulate stroke volume?

    <p>Myocardial contractility, cardiac afterload, and cardiac preload</p> Signup and view all the answers

    How does vessel dilation affect blood flow?

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

    What happens to cardiac output (CO) when heart rate is increased?

    <p>CO increases, provided stroke volume is stable</p> Signup and view all the answers

    Which statement best describes preload in the context of the heart?

    <p>It is the tension applied to the cardiac muscle before contraction.</p> Signup and view all the answers

    What is the primary effect of increased afterload on stroke volume (SV)?

    <p>SV decreases as the heart struggles against the increased load</p> Signup and view all the answers

    According to the Starling Law of the Heart, what effect does increased venous return have on cardiac output?

    <p>It increases ventricular diameter and consequently cardiac output.</p> Signup and view all the answers

    What primarily regulates heart rate under normal physiological conditions?

    <p>Autonomic nervous system activity</p> Signup and view all the answers

    What causes pressure to drop progressively throughout the systemic circulation?

    <p>Resistance from various vessel lengths and diameters</p> Signup and view all the answers

    Which factor does NOT contribute to cardiac afterload?

    <p>Ventricular filling pressure</p> Signup and view all the answers

    What mechanism primarily generates negative pressure in the right atrium to assist in venous return?

    <p>Chest expansion during inspiration</p> Signup and view all the answers

    What is the average cardiac output for an adult in liters per minute?

    <p>5.0 L/min</p> Signup and view all the answers

    What is the primary mechanism by which the Renin-Angiotensin-Aldosterone System (RAAS) raises arterial pressure?

    <p>Vasoconstriction of arterioles</p> Signup and view all the answers

    Which response occurs immediately after a drop in arterial pressure due to the baroreceptor reflex?

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

    What is the effect of postural hypotension on cardiac output when changing positions?

    <p>Decreases cardiac output due to venous pooling</p> Signup and view all the answers

    How do kidneys respond to low arterial pressure over a prolonged period?

    <p>Retain water and sodium</p> Signup and view all the answers

    What is a key action of atrial natriuretic peptide (ANP) in response to high blood volume?

    <p>Increase venous capacitance</p> Signup and view all the answers

    What consequence arises from administering a drug that dilates veins?

    <p>Exacerbated postural hypotension</p> Signup and view all the answers

    What primarily causes renal blood flow and glomerular filtration rate (GFR) reduction when arterial pressure is low?

    <p>Decreased renal perfusion pressure</p> Signup and view all the answers

    Which of the following mechanisms can help restore arterial pressure during postural hypotension?

    <p>Activation of the baroreceptor reflex</p> Signup and view all the answers

    Which is a primary role of C-natriuretic peptide (CNP)?

    <p>Induce vasodilation</p> Signup and view all the answers

    What is the effect of aldosterone during low arterial pressure events?

    <p>Increases sodium and water retention</p> Signup and view all the answers

    What physiological change occurs due to excessive blood volume related to natriuretic peptides?

    <p>Decreased arterial pressure</p> Signup and view all the answers

    In relation to heart failure, how do ANP and BNP protect the heart?

    <p>Suppress RAAS and sympathetic outflow</p> Signup and view all the answers

    What is the immediate response of the cardiovascular system when a person stands up quickly?

    <p>Pooling of blood in the lower extremities</p> Signup and view all the answers

    What role does angiotensin II primarily play in the RAAS?

    <p>Stimulate aldosterone secretion</p> Signup and view all the answers

    What primarily determines the stroke volume (SV) of the heart?

    <p>Venous return</p> Signup and view all the answers

    What effect does venodilation have on systemic filling pressure?

    <p>It lowers systemic filling pressure.</p> Signup and view all the answers

    How does sympathetic tone influence the autonomic nervous system's control of arterial pressure (AP)?

    <p>It increases heart rate and contractility.</p> Signup and view all the answers

    What role does right atrial pressure play in venous return?

    <p>Impairs venous return when elevated.</p> Signup and view all the answers

    Which of the following describes the relationship defined by Starling's law?

    <p>Increased ventricular filling leads to increased force of contraction.</p> Signup and view all the answers

    What is the effect of the baroreceptor reflex when arterial pressure rises too high?

    <p>It dilates arterioles and slows the heart.</p> Signup and view all the answers

    In the context of peripheral resistance, which factor can lead to an increase in arterial pressure (AP)?

    <p>Increased resistance due to arteriolar constriction</p> Signup and view all the answers

    Which factor can directly influence venous return through pharmacological means?

    <p>Increased blood volume</p> Signup and view all the answers

    What happens to the baroreceptor reflex if arterial pressure remains elevated for a prolonged duration?

    <p>It resets to the new pressure level.</p> Signup and view all the answers

    What occurs if the heart fails in accordance with Starling's law?

    <p>It leads to pulmonary congestion due to output discrepancies.</p> Signup and view all the answers

    Which system provides long-term regulation of arterial pressure?

    <p>Renin-angiotensin-aldosterone system (RAAS)</p> Signup and view all the answers

    Which statement is true regarding the actions of the autonomic nervous system on cardiac output (CO)?

    <p>Parasympathetic activity decreases CO while sympathetic activity increases it.</p> Signup and view all the answers

    What impact does constriction of veins have on systemic filling pressure?

    <p>It raises systemic filling pressure.</p> Signup and view all the answers

    Study Notes

    Hemodynamics Overview

    • Hemodynamics studies blood movement, regulation, and driving forces in the circulatory system.
    • It is crucial for understanding how cardiovascular drugs work.
    • The circulatory system delivers essentials (oxygen, nutrients, hormones, electrolytes) to cells and removes waste (carbon dioxide, metabolic wastes).
    • It has two divisions: pulmonary (lungs) and systemic (other organs).
    • The pulmonary circulation delivers blood to the lungs. The systemic circulation delivers blood to all other organs and tissues. Systemic circulation is also known as the greater or peripheral circulation.

    Circulatory System Components

    • The system comprises the heart and blood vessels.
    • Arteries transport blood under high pressure to tissues.
    • Arterioles regulate local blood flow.
    • Capillaries are the sites for exchange of fluid, oxygen, carbon dioxide, nutrients, hormones, and wastes.
    • Venules collect blood from capillaries.
    • Veins transport blood back to the heart; they act as a blood reservoir.
    • Arteries are less distensible (elastic) than veins. Veins are 6-10 times more distensible, meaning small increases in venous pressure cause large increases in vessel diameter, which produce a large increase in venous volume.

    Blood Distribution

    • The average adult has ~5L of blood.
    • Blood is distributed unevenly: mostly in veins (64%), with less in arteries (13%) and capillaries (7%) of the systemic circulation.
    • Pulmonary circulation and heart hold smaller portions (9% and 7%, respectively).

    Blood Flow Dynamics

    • Blood flows from higher to lower pressure.
    • Pressure gradient drives flow.
    • Resistance is determined by vessel diameter, length, and viscosity.
    • Larger vessels have lower resistance, leading to increased flow with dilation and decreased flow with constriction.
    • Blood flow is maintained when resistance rises by increasing blood pressure accordingly.

    Pressure Changes in Systemic Circulation

    • Blood pressure in the aorta is ~120 mm Hg.
    • It gradually drops to ~18 mm Hg in capillaries and even more negative (0-5 mm Hg) in the right atrium.
    • Inspiration (chest expansion) generates negative atrial pressure.
    • Venous return is crucial for blood movement back to the heart despite low capillary pressure. Three mechanisms ensure venous return: negative pressure in the right atrium, venous smooth muscle contraction, and the venous valve and skeletal muscle pump.

    Venous Return Mechanisms

    • Negative pressure in the right atrium pulls blood toward the heart.
    • Venous smooth muscle contraction increases venous pressure, aiding blood return.
    • Venous valves and skeletal muscle contractions act as a venous pump, promoting blood movement toward the heart.

    Cardiac Output

    • Cardiac output (CO) is the volume of blood pumped per minute (~5L/min).
    • The formula is CO = Heart Rate (HR) × Stroke Volume (SV).
    • Increases in HR or SV increase CO; decreases decrease CO.
    • The average HR is ~70 beats/min and SV is ~70 mL, resulting in an average CO of ~4.9 L/min.

    Heart Rate Regulation

    • The autonomic nervous system (ANS) controls heart rate.
    • The sympathetic nervous system increases rate via beta-1 adrenergic receptors in the SA node.
    • The parasympathetic nervous system decreases rate via muscarinic receptors in the SA node, with impulses via the vagus nerve.

    Stroke Volume Regulation

    • Stroke volume (SV) depends on myocardial contractility, cardiac afterload, and preload.
    • Myocardial contractility, determined by cardiac dilation (venous return), is influenced by sympathetic nervous system activity (beta-1 adrenergic receptors).

    Preload

    • Preload is the stretch on the heart before contraction, primarily determined by ventricular filling pressure (venous return).
    • Increased preload = increased stroke volume; decreased preload = decreased stroke volume.
    • End-diastolic volume (EDV) and end-diastolic pressure (EDP) are measures of preload.

    Afterload

    • Afterload is the resistance against which the heart contracts (left ventricular pressure to eject blood).
    • Increased afterload = decreased stroke volume; decreased afterload = increased stroke volume.
    • Peripheral resistance (arteriole constriction/dilation) impacts afterload.

    Starling's Law of the Heart

    • Heart contraction force is proportional to fiber length (ventricular diameter), up to a point.
    • Increased venous return increases cardiac output proportionally.
    • This maintains systemic and pulmonary blood flow balance in a healthy heart.

    Venous Return Determinants

    • Systemic filling pressure (7 mm Hg) is crucial. Increased or decreased pressure is achieved via vein constriction/dilation, potentially influenced by alterations in blood volume.
    • Auxiliary muscle pumps, flow resistance, and atrial pressure affect venous return.

    Systemic-Pulmonary Balance

    • A failure in Starling's mechanism causes one ventricle to pump less blood than the other.
    • This imbalance leads to blood backup into the pulmonary circulation (pulmonary congestion).
    • The myocardium operates in accordance with Starling's law to maintain both sides in balance.

    Arterial Pressure (AP)

    • AP is the driving force for blood through arteries; AP = Peripheral Resistance (PR) × Cardiac output (CO).
    • Increased PR or CO increases AP; decreased PR or CO decreases AP.
    • Peripheral resistance is controlled by arteriolar constriction/dilation.
    • Cardiac output is regulated by factors previously discussed.

    Overview of Control Systems

    • AP is regulated by the autonomic nervous system, the renin-angiotensin-aldosterone system (RAAS), the kidneys, and natriuretic peptides.

    Autonomic Nervous System Control (Steady State)

    • Sympathetic tone increases heart rate and contractility, leading to increased CO.
    • Parasympathetic tone slows the heart, decreasing CO.
    • Sympathetic tone causes moderate vasoconstriction to maintain AP.
    • Absence of sympathetic tone significantly lowers AP.

    Baroreceptor Reflex

    • Maintains AP via a rapid feedback loop.
    • Baroreceptors sense AP changes, sending signals to the medulla for proper adjustments to arterioles, veins, and the heart.

    Renin-Angiotensin-Aldosterone System (RAAS)

    • Influences AP through vasoconstriction (angiotensin II) and water retention (aldosterone).

    Renal Water Retention

    • Low AP reduces renal blood flow and glomerular filtration rate, causing water retention to raise AP.
    • Reduced AP also triggers the RAAS, increasing angiotensin II and aldosterone to further reduce renal blood flow and increase sodium retention, leading to water retention.

    Postural Hypotension (Orthostatic Hypotension)

    • Reduced AP when moving from supine to upright positions due to blood pooling in veins and reduced venous return.
    • Auxiliary muscle pumps and the baroreceptor reflex help manage/recover from postural hypotension. Drugs that prevent venoconstriction prolong and intensify postural hypotension.

    Natriuretic Peptides

    • Protect against volume overload by reducing blood volume, promoting vasodilation, and impacting preload and blood pressure.
    • ANP, BNP, and CNP are three notable peptides, each with similar but differentiated mechanisms. ANP is from the atria, BNP from the ventricles, and CNP from vascular endothelium. Their release is signaled by increased preload due to volume overload. They cause diuresis, natriuresis, and vasodilation to lower blood pressure. They also impact the RAAS and sympathetic outflow as part of heart failure protection.

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    Description

    This quiz covers the essential concepts of hemodynamics, focusing on the movement of blood in the circulatory system and the roles of various components. It highlights the significance of blood distribution across different vessels and how cardiovascular drugs interact with these processes. Test your knowledge on the heart, blood vessels, and the function of the circulatory system.

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