Vascular Physiology Lecture 3

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Questions and Answers

What condition is most likely to result in a higher pulse wave velocity?

  • Stiff central arteries (correct)
  • Decreased blood pressure
  • Increased physical activity
  • Lower heart rate

Which phase of the cardiac cycle is affected by the backward-traveling pulse wave in patients with stiff arteries?

  • Isovolumetric relaxation
  • Early diastole
  • Late filling
  • Systole (correct)

What is one potential outcome of elevated pulse wave velocity in patients with stiff arteries?

  • Augmentation of aortic systolic pressure (correct)
  • Decreased pulse pressure
  • Elimination of inflection points
  • Prolonged diastolic filling time

Which patient demographic is more likely to have stiff central arteries?

<p>Elderly patients (B)</p> Signup and view all the answers

What is the primary factor leading to the premature arrival of the backward-traveling pulse wave?

<p>Higher pulse wave velocity (B)</p> Signup and view all the answers

What property of elastic arteries allows them to stretch during systole?

<p>Distensability (B)</p> Signup and view all the answers

Which phase of the cardiac cycle is primarily associated with elastic recoil in elastic arteries?

<p>Diastole (C)</p> Signup and view all the answers

What is the main function of elastic arteries during the cardiac cycle?

<p>To maintain a continuous blood flow (D)</p> Signup and view all the answers

What mechanism does the heart use to exert pressure on the elastic arteries?

<p>Systolic ejection (D)</p> Signup and view all the answers

Which statement correctly describes the walls of elastic arteries?

<p>Abundant in elastic tissue to allow distensability (A)</p> Signup and view all the answers

What is the primary function of elastic vessels during ventricular diastole?

<p>They increase the velocity of blood flow. (C)</p> Signup and view all the answers

How does the windkessel effect benefit the heart?

<p>By reducing energy expenditure of the heart. (D)</p> Signup and view all the answers

What occurs as a result of elastic recoil in blood vessels during diastole?

<p>Blood flow velocity increases. (D)</p> Signup and view all the answers

What effect does elastic recoil have on the blood flow during diastole?

<p>It enhances the preservation of kinetic energy. (C)</p> Signup and view all the answers

Which statement best describes the influence of elastic vessels on heart function?

<p>They assist in the energy-efficient flow of blood. (C)</p> Signup and view all the answers

What is considered the reference point for assessing arterial and venous pressure?

<p>The heart (D)</p> Signup and view all the answers

How does gravity primarily affect venous pressure in the body?

<p>It increases venous pressure in the lower extremities. (A)</p> Signup and view all the answers

In terms of venous pressure, what role does the heart play?

<p>It acts as a reference point for measurement. (A)</p> Signup and view all the answers

Which factor is least likely to affect venous pressure?

<p>Temperature (B)</p> Signup and view all the answers

What physiological effect does gravity have on the circulation of blood in the body?

<p>It creates a pressure gradient that affects blood return to the heart. (C)</p> Signup and view all the answers

What primarily increases the venous pressure below the heart?

<p>Force of gravity (C)</p> Signup and view all the answers

What happens to the neck veins when the venous pressure is close to zero?

<p>They collapse (D)</p> Signup and view all the answers

What pressure condition exists along the collapsed segment of the neck veins?

<p>Close to zero pressure (D)</p> Signup and view all the answers

Which statement is true regarding venous pressure and gravity?

<p>Gravity increases venous pressure below the heart. (A)</p> Signup and view all the answers

Which statement best describes the relationship between neck veins and venous pressure?

<p>Neck veins collapse above the point where venous pressure is close to zero. (B)</p> Signup and view all the answers

What happens to blood in the lower parts of the body when gravitational force is acting in an erect posture?

<p>Gravity causes an increase in venous pressure in the lower limbs. (C)</p> Signup and view all the answers

How does the gravitational force influence venous return from the lower limbs?

<p>It decreases venous return from the lower limbs. (C)</p> Signup and view all the answers

In an erect posture, the effect of gravity on the body's venous pressure is most pronounced in which areas?

<p>Dependent parts of the body. (B)</p> Signup and view all the answers

What is the primary consequence of increased pressure in the veins of the lower limbs due to gravity?

<p>Stasis of blood in the lower veins. (B)</p> Signup and view all the answers

Which of the following best describes the relationship between gravitational force and venous pressure in the lower body?

<p>Gravitational force leads to increased venous pressure in the dependent areas. (C)</p> Signup and view all the answers

Flashcards

Pulse Wave Velocity (PWV)

The speed at which a pressure wave travels through an artery.

Stiff Central Arteries

The condition where the arteries become stiff and less flexible, often associated with age or atherosclerosis.

Reflected Wave

The backward-traveling wave of pressure that reflects back from the periphery.

Inflection Point

The point on the pressure waveform where the reflected wave meets the forward wave, causing a change in the waveform.

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Augmentation of Aortic Systolic Pressure

The increased pressure in the aorta during systole due to the arrival of the reflected wave.

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Distensability of arteries

The ability of a vessel to stretch or expand in response to increased pressure.

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Elastic Recoil of arteries

The ability of a vessel to return to its original size after being stretched.

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Systole

The phase of the heartbeat when the heart contracts and pumps blood.

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Diastole

The phase of the heartbeat when the heart relaxes and fills with blood.

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Elastic Arteries

Arteries that have a large amount of elastic tissue in their walls. They are able to stretch and recoil, which helps to maintain blood flow.

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Elasticity of blood vessels

The ability of blood vessels, specifically arteries, to expand and contract due to pressure changes.

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What is ventricular diastole?

The decrease in blood pressure that occurs between heartbeats (ventricular diastole).

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Windkessel effect

The expansion of the arteries during ventricular systole and the recoil of the arteries during ventricular diastole helps maintain a constant blood flow despite the intermittent pumping of the heart.

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Energy expenditure of the heart

The energy the heart uses to pump blood.

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How the Windkessel effect saves energy

The ability of the Windkessel effect to reduce the heart's energy expenditure by maintaining a constant blood flow.

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Gravitational force

The force of attraction between any two objects with mass.

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Gravity's effect on Venous pressure

The force of gravity affects the pressure within veins.

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Heart as a reference point

The point used for measuring pressures in the circulatory system.

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Venous Pressure and Gravity

The pressure in veins below the heart is higher due to gravity.

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Venous Collapse

When the pressure in veins is close to zero, the veins collapse above that point.

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Collapsed Vein Pressure

A collapsed segment of a vein has a pressure close to zero, not below atmospheric pressure.

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Pressure in a Collapsed Vein

The pressure in a collapsed segment of a vein is essentially the same as the surrounding air pressure.

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Venous Pressure

Venous pressure is the pressure of blood inside veins.

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Gravity

The force that pulls objects towards each other, like the force that pulls us towards the Earth.

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Gravitational Force on Blood

The force that gravity exerts on blood in your body, especially when you stand up.

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Venous Return

The amount of blood returning to your heart from your legs is reduced when gravity pulls blood down.

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Gravity's Effect on Veins

The force of gravity impacts blood flow in veins, especially in your lower legs when you're standing upright.

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Study Notes

Vascular Physiology Lecture 3

  • The lecture covers arterial pulse, elastic arteries, delayed compliance, and gravitational forces on the cardiovascular system (CVS).

Overview

  • Concept 1: Arterial Pulse
  • Concept 2: Elastic arteries
  • Concept 3: Delayed compliance
  • Concept 4: Changes in CVS caused by gravitational forces

Concept 1: Arterial Pulse

  • Blood flows through the circulatory system, exiting the left ventricle and entering the aorta.
  • During systole, the left ventricle contracts, forcing blood into the ascending aorta. The aortic wall dilates, creating a pressure wave (pulse wave) that travels through the arteries.
  • The pressure wave expands arterial walls, creating a palpable pulse.
  • Features of the pulse wave (or pressure wave):
    • Systolic pressure: Peak pressure (e.g., 120 mmHg)
    • Diastolic pressure: Lowest pressure (e.g., 80 mmHg)
    • Diastolic pressure corresponds to end ventricular diastolic pressure and the opening of the aortic valve.
    • Note: Diastolic pressure in the aorta is not equal to diastolic pressure in the ventricle.

Concept 2: Elastic Arteries

  • Large arteries (e.g., aorta, carotid, iliac, axillary arteries) contain elastic tissues.
  • These arteries exhibit two main properties that contribute to blood flow
    • Distensibility (in Systole): The ability of arteries to expand to accommodate the blood pumped by the heart with a relatively moderate increase in pressure.
    • Elastic recoil (in Diastole): The ability of elastic arteries to return to their original shape and exert this potential energy on blood, facilitating continuous blood flow even during diastole.

Concept 3: Delayed Compliance

  • The term "delayed compliance" describes how blood vessels react when their volume increases.
  • At first, there is a substantial pressure increase, but the progressive stretching of smooth muscles in vessel walls eventually allows the pressure to return to normal levels (minutes to hours).
  • In other words: A sudden increase in blood volume momentarily elevates pressure, but subsequent relaxation of the vessel walls progressively reduces the pressure over time.

Concept 4: Gravitational Forces

  • Gravity affects hydrostatic pressure in the body's fluid systems, including the cardiovascular system

  • Hydrostatic pressure: Force exerted by fluids at rest due to gravity.

    • Factors: Acceleration of gravity (g), height (h), and density (ρ)
      • The formula: P = pgh
  • In a supine (lying down) position, the cardiovascular system is roughly at the same horizontal level, mitigating hydrostatic pressure variance.

  • Vertical differences are consequential. Blood in the lower extremities increases pressure there, but reduces pressure in the upper parts of the body.

  • Effect of gravity on venous pressure: In the upright position,

    • Decreases venous pressure in body parts above the heart.
    • Increases venous pressure in body parts below the heart.
  • Effect of gravity on arterial pressure:

    • Adds 0.77 mmHg to arterial pressure for each cm below the heart.
    • Subtracts 0.77 mmHg from arterial pressure for each cm above the heart.

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