Cardiovascular Physiology: Arterial Pressure Regulation

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Questions and Answers

What effect does a decrease in total peripheral resistance (TPR) have on the vascular function curve?

Rotates clockwise, resulting in a steeper slope. (correct)

Rotates counterclockwise, resulting in a steeper slope.

Rotates clockwise, resulting in a flatter slope.

Rotates counterclockwise, resulting in a flatter slope.

What happens to the mean systemic filling pressure when there is an increase in blood volume?

It increases, shifting the vascular function curve to the right. (correct)

It decreases, shifting the vascular function curve to the right.

It decreases, shifting the vascular function curve to the left.

It increases, shifting the vascular function curve to the left.

Which of the following accurately describes the relationship between venous return and right atrial pressure in the context of a steeper vascular function curve?

Venous return decreases for a given right atrial pressure.

Venous return increases more significantly for a given right atrial pressure. (correct)

Venous return remains constant for a given right atrial pressure.

Venous return decreases less significantly for a given right atrial pressure.

What is the primary factor determining the slope of the vascular function curve?

Total peripheral resistance (D) Signup and view all the answers

Which of the following conditions would lead to a flatter vascular function curve?

Decreased venous compliance (D) Signup and view all the answers

How does an increase in blood volume affect the intersection point on the vascular function curve where venous return is zero?

Shifts it to the right. (B) Signup and view all the answers

If the mean systemic filling pressure is constant, what can cause a change in the slope of the vascular function curve?

Changes in total peripheral resistance. (B) Signup and view all the answers

Which of the following is NOT a factor that directly influences mean systemic filling pressure?

Total peripheral resistance (C) Signup and view all the answers

What is the relationship between venous return and right atrial pressure?

Inversely proportional (D) Signup and view all the answers

How does an increase in arteriolar resistance affect blood flow from the arterial to the venous side of the circulation?

Decreases the rate of blood flow. (D) Signup and view all the answers

What causes the knee (flat portion) of the vascular function curve?

Venous collapse (D) Signup and view all the answers

What is the mean systemic filling pressure?

The pressure in the right atrium when venous return is zero (D) Signup and view all the answers

What happens to blood flow when the mean systemic filling pressure is reached?

Blood flow stops (D) Signup and view all the answers

What are the two factors that influence the mean systemic filling pressure?

Blood volume and distribution of blood (A) Signup and view all the answers

Which of the following best describes the relationship between unstressed volume and stressed volume?

Unstressed volume is the volume of blood in the blood vessels when they are at their resting state, while stressed volume is the volume of blood when the vessels are distended. (A) Signup and view all the answers

What is the main factor that determines the intersection point (zero flow) of the vascular function curve with the X-axis?

Mean systemic filling pressure (B) Signup and view all the answers

What is the primary effect of Ang 1-7 on the cardiovascular system?

Vasodilation (D) Signup and view all the answers

Which of the following is NOT a direct effect of angiotensin II on the body?

Increased sodium reabsorption in the collecting ducts (C) Signup and view all the answers

Which hormone is primarily responsible for increasing sodium reabsorption in the kidneys?

Aldosterone (B) Signup and view all the answers

What is the role of ACE2 in the renin-angiotensin system?

It degrades angiotensin II to Ang 1-7 (C) Signup and view all the answers

How does angiotensin II contribute to an increase in blood pressure?

By causing vasoconstriction (B) Signup and view all the answers

Which of the following is an effect of angiotensin II that is NOT related to blood pressure regulation?

Pro-oxidative stress (A), Pro-fibrotic (B), Pro-proliferative (C), Pro-inflammatory (D) Signup and view all the answers

How does angiotensin II affect the release of antidiuretic hormone (ADH)?

It stimulates the release of ADH (A) Signup and view all the answers

What is the primary mechanism by which an increase in blood volume contributes to an increase in blood pressure?

Increased stroke volume (C) Signup and view all the answers

Which of the following statements correctly describes the relationship between angiotensin II and Ang 1-7?

They are produced by different enzymes and have opposite effects (B) Signup and view all the answers

Which of the following is directly responsible for the degradation of angiotensin II?

ACE2 (C) Signup and view all the answers

What occurs in response to a significant blood loss to restore arterial pressure?

Increase in total peripheral resistance (TPR) (B) Signup and view all the answers

Which statement accurately describes the effect of central command during exercise?

It directs an increase in sympathetic outflow. (D) Signup and view all the answers

How does exercising skeletal muscle influence venous return?

Through the muscle's squeezing action on the veins. (C) Signup and view all the answers

What is the relationship between venous return and cardiac output in the context of exercise?

Increased venous return allows for increased cardiac output. (B) Signup and view all the answers

What is the effect of hemorrhage on the carotid sinus nerve firing rate?

It decreases. (A) Signup and view all the answers

What is the primary force driving fluid movement across capillary walls?

A combination of hydrostatic and effective osmotic pressure (C) Signup and view all the answers

What role do proteins play in fluid movement across capillaries?

Proteins contribute to effective osmotic pressure (D) Signup and view all the answers

In which type of capillary are proteins most likely to pass freely?

Intestinal capillaries (B) Signup and view all the answers

What is the main function of the lymphatic system?

Returning interstitial fluid and proteins to the vascular compartment (D) Signup and view all the answers

Which of the following factors contributes to lymph flow back to the thoracic duct?

All of the above (D) Signup and view all the answers

Why are the lymphatic capillaries considered one-way valves?

They possess flap valves that allow fluid and protein to enter but not exit (C) Signup and view all the answers

What is the significance of the reflection coefficient in relation to effective osmotic pressure?

It indicates the permeability of the membrane to a particular solute (C) Signup and view all the answers

Which of the following is NOT a characteristic of brain capillaries?

Presence of fenestrations (B) Signup and view all the answers

What is the primary function of the thoracic duct?

Collecting and transporting lymph from the lower body and left side of the upper body (B) Signup and view all the answers

Which of the following statements about the lymphatic system is CORRECT?

The lymphatic system plays a vital role in maintaining fluid balance (D) Signup and view all the answers

Which type of capillaries allows the passage of limited amounts of protein due to being fenestrated?

Kidney and intestinal capillaries (A) Signup and view all the answers

What primarily contributes to the effective osmotic pressure in capillary blood?

Proteins (D) Signup and view all the answers

How do lymphatic capillaries facilitate the return of interstitial fluid and proteins to the vascular compartment?

By employing one-way flap valves (D) Signup and view all the answers

Which statement best describes how fluid movement across capillary walls is driven?

By the sum of hydrostatic and effective osmotic pressures (A) Signup and view all the answers

What is the role of smooth muscle in lymphatic vessels?

To promote lymph flow through contraction (A) Signup and view all the answers

What is the primary role of renin in the body?

To convert angiotensinogen to angiotensin I (B) Signup and view all the answers

How does angiotensin II directly affect the kidneys?

By stimulating sodium-H⁺ exchange (B) Signup and view all the answers

What is the expected effect of an ACE inhibitor like captopril?

Decreased production of aldosterone (C) Signup and view all the answers

Which receptor type does angiotensin II primarily activate to exert its effects?

AT₁ receptors (D) Signup and view all the answers

What mechanism primarily accounts for the slow response time of the renin-angiotensin II-aldosterone system?

Production of new proteins in the kidney (C) Signup and view all the answers

What role do precapillary sphincters play in the microcirculation?

They determine blood flow into the capillary bed. (D) Signup and view all the answers

How does vasoconstriction of arterioles affect blood flow to capillaries?

It decreases blood flow to the capillaries. (A) Signup and view all the answers

What regulates the contractile state of arteriolar vascular smooth muscle?

Neural, endocrine, and paracrine factors. (B) Signup and view all the answers

What anatomical feature primarily facilitates the exchange of nutrients and waste in tissues?

Capillaries. (B) Signup and view all the answers

What structure precedes the capillaries and is involved in regulating blood flow?

Metarterioles. (D) Signup and view all the answers

Study Notes

Cardiovascular Physiology Regulation of Arterial Pressure

Cardiac output is determined by left ventricular end-diastolic volume, which depends on venous return
Right atrial pressure is linked to left ventricular end-diastolic volume
Cardiac output and venous return have a relationship that can be visualized through graphs
Cardiac function curve (Figure 4.26) plots the relationship between cardiac output and right atrial pressure, based on the Frank-Starling relationship for the left ventricle.
Cardiac output increases with increasing venous return (right atrial pressure) up to a certain point (approximately 4 mm Hg right atrial pressure).
Maximum cardiac output is approximately 9 L/min
Vascular function curve (Figure 4.26) depicts the relationship between venous return and right atrial pressure.
Venous return is blood flow through the systemic circulation back to the right heart
Venous return is inversely related to right atrial pressure, meaning higher right atrial pressure results in lower venous return
Mean systemic filling pressure is the value of right atrial pressure at which venous return is zero.
Mean systemic filling pressure is determined by blood volume and the distribution of blood between the unstressed volume and the stressed volume.
Blood volume changes affect mean systemic filling pressure by shifting the vascular function curve.
Increased blood volume shifts the curve to the right, while decreased blood volume shifts the curve to the left
Compliance of veins affects the curve shift
Increased venous compliance decreases mean systemic filling pressure (and vice-versa)
Total Peripheral Resistance (TPR) affects the slope of the vascular function curve:
- Decreasing TPR makes the slope steeper, increasing venous return with small changes in right atrial pressure.
- Increasing TPR makes the slope flatter, decreasing venous return with small changes in right atrial pressure.
Changes in TPR affect both the cardiac function curve and the vascular function curve
Blood volume and venous compliance change the mean systemic filling pressure and thus shift the vascular function curve to the right or left in a parallel manner
The effects of changes in blood volume or venous compliance are parallel shifts (one example is shown in Figure 4.29)
Changes in total peripheral resistance (TPR) affect the slope of the vascular function curve.
- Increased TPR causes a clockwise rotation, resulting in a flatter slope.
- Decreased TPR causes a counterclockwise rotation, resulting in a steeper slope.
Increased TPR leads to decreased cardiac output and reduced venous return.
Decreased TPR leads to increased cardiac output and increased venous return.
The mechanisms regulating blood pressure are complex and involve central nervous system (CNS) and local control mechanisms.
Local control of blood flow is primarily in charge of matching blood flow to the metabolic demand of the tissues
The central command is a series of responses initiated by the anticipation of exercise. It triggers increased sympathetic outflow to the heart (increasing heart rate and contractility), and blood vessels, as well as decreased parasympathetic outflow.
The central command leads to selective vasoconstriction in non-exercising tissues (in an attempt to redistribute blood flow) and vasodilation in exercising skeletal muscle tissues.
Local metabolites (such as lactate, K+, and adenosine) cause vasodilation, increasing blood flow in exercising tissue (active hyperemia), and help meet the increased oxygen demand.
Decreased blood flow to a tissue, such as during occlusion, activates reactive hyperemia
Hypoxia (low O2), a local metabolic factor, also affects blood flow.
The cerebral, pulmonary, skin, and skeletal muscle circulations respond to local metabolites and CNS control to ensure appropriate blood flow in each tissue.
Hemorrhage (blood loss) elicits compensatory responses:
- Increased heart rate, contractility, and cardiac output
- Increased total peripheral resistance
- Increased renin, angiotensin II, and aldosterone.
- Increased circulating epinephrine and ADH
Posture changes (e.g., from lying to standing) have compensatory cardiovascular responses.

Regulation of Microcirculation

Vasoconstriction and vasodilation of arterioles control blood flow into capillaries
Mediators (e.g., norepinephrine, angiotensin II, adenosine) cause vasoconstriction
Mediators (e.g., adenosine, K+, histamine) cause vasodilation

Exchange of Substances Across the Capillary Wall

Movement of substances across capillaries is primarily through simple diffusion.
Lipid-soluble substances (e.g., O2, CO2) diffuse readily.
Water-soluble substances (e.g., ions, glucose) diffuse through aqueous channels between cells.
Hydrostatic and osmotic pressures (Starling pressures) are critical in fluid movement across capillaries.
Colloid osmotic pressure, influenced by protein concentration, drives fluid absorption.

Lymph

Lymph capillaries collect interstitial fluid and proteins, returning them to circulation.
Lymphatic vessels return fluids to the cardiovascular system, which helps maintain fluid balance.

Integrative Functions of the Cardiovascular System

Blood flow in different tissues is finely tuned and regulated in coordination with the cardiovascular system.
The central nervous system (CNS) plays a key role in regulating cardiovascular function from anticipation of exercises to blood loss.
Local metabolites (tissue-specific factors) also direct blood flow to suit the specific need of each tissue.

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Description

Explore the intricacies of cardiac output and venous return in relation to arterial pressure. This quiz covers key concepts such as the Frank-Starling mechanism, cardiac function curves, and vascular function curves. Test your understanding of how right atrial pressure influences cardiovascular dynamics.