Blood Vessel Compliance and Function Quiz
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Questions and Answers

What is the relationship between compliance, distensibility, and volume in blood vessels?

  • Compliance is inversely proportional to distensibility.
  • Compliance depends solely on the volume of the vessel.
  • Compliance is the square of distensibility.
  • Compliance is equal to distensibility times volume. (correct)

    • Why is the compliance of systemic veins much greater than that of systemic arteries?

  • Systemic veins are less distensible.
  • Systemic veins are located closer to the heart.
  • Systemic veins have more blood.
  • Systemic veins are more distensible and have a larger volume. (correct)

    • When the arterial system is filled with 700 ml of blood, what is the mean arterial pressure?

  • 75 mm Hg
  • 50 mm Hg
  • 150 mm Hg
  • 100 mm Hg (correct)

    • How much change in volume is required in the systemic venous system to affect venous pressure significantly?

    <p>Several hundred milliliters (A)</p> Signup and view all the answers

    What effect does sympathetic stimulation have on vascular smooth muscle tone?

    <p>It increases the pressure at each volume. (C)</p> Signup and view all the answers

    What is a principal method by which the body increases heart pumping during increased vascular tone?

    <p>Shifting large volumes of blood into the heart. (D)</p> Signup and view all the answers

    During hemorrhage, what role does sympathetic control of vascular capacitance play?

    <p>It constricts vessel sizes to maintain circulation. (C)</p> Signup and view all the answers

    What volume range does the systemic venous system typically contain?

    <p>2000 to 3500 milliliters (B)</p> Signup and view all the answers

    What is the primary function of the distensible nature of arteries?

    <p>To allow smooth, continuous blood flow (C)</p> Signup and view all the answers

    How does the distensibility of veins compare to that of arteries?

    <p>Veins are about eight times more distensible than arteries (A)</p> Signup and view all the answers

    What defines vascular compliance or capacitance?

    <p>The total blood volume stored per mm Hg pressure increase (C)</p> Signup and view all the answers

    What is expressed by the formula for vascular distensibility?

    <p>The fractional increase in volume per mm Hg rise in pressure (C)</p> Signup and view all the answers

    Which statement accurately describes pulmonary circulation compared to systemic circulation?

    <p>Pulmonary arteries have greater distensibility than systemic arteries (D)</p> Signup and view all the answers

    What happens to veins during slight increases in venous pressure?

    <p>They store an additional 0.5 to 1.0 liter of blood (D)</p> Signup and view all the answers

    Why is compliance more important than distensibility in hemodynamic studies?

    <p>It shows the total blood volume that can be stored at a certain pressure (B)</p> Signup and view all the answers

    If a blood vessel originally containing 10 milliliters increases its volume by 1 milliliter at 1 mm Hg, what is the vascular distensibility?

    <p>0.1 per mm Hg (C)</p> Signup and view all the answers

    What primarily determines pulse pressure?

    <p>Stroke volume output and arterial compliance (D)</p> Signup and view all the answers

    What happens to pulse pressure as arteries become more noncompliant with age?

    <p>Pulse pressure can increase to twice normal (D)</p> Signup and view all the answers

    What is the velocity of pressure pulse transmission in the normal aorta?

    <p>3 to 5 m/sec (B)</p> Signup and view all the answers

    What two factors contribute to the damping of pressure pulses?

    <p>Resistance to blood movement and compliance of the vessels (B)</p> Signup and view all the answers

    How does increased arterial resistance impact pulse pressure?

    <p>It reduces pulse pressure (B)</p> Signup and view all the answers

    What role does compliance play in the transmission of pressure pulses?

    <p>Increased compliance slows down pulse transmission (A)</p> Signup and view all the answers

    What primarily causes the initial distention of the aorta during systole?

    <p>Inertia of the blood (B)</p> Signup and view all the answers

    Which statement accurately describes the relationship between stroke volume and arterial compliance?

    <p>Higher stroke volume typically results in higher pulse pressure if compliance is low (C)</p> Signup and view all the answers

    What is the typical lower limit of right atrial pressure in mm Hg?

    <p>-3 to -5 mm Hg (C)</p> Signup and view all the answers

    What causes the right atrial pressure to approach lower values?

    <p>Severe hemorrhage (A)</p> Signup and view all the answers

    What effect does increased compliance of a vessel have on pressure pulses?

    <p>It dampens the pulsations of pressure. (A)</p> Signup and view all the answers

    When does blood begin to back up in the large veins?

    <p>When right atrial pressure rises above +4 to +6 mm Hg (C)</p> Signup and view all the answers

    What physiological mechanism allows veins to propel blood forward?

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

    What is the pressure in small peripheral veins when a person is lying down compared to right atrial pressure?

    <p>About +4 to +6 mm Hg greater (D)</p> Signup and view all the answers

    Which factor would NOT contribute to an increase in right atrial pressure?

    <p>Decreased large vessel tone (C)</p> Signup and view all the answers

    What is a common cause for elevated intra-abdominal pressure?

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

    Under what condition can right atrial pressure increase to very abnormal levels?

    <p>Serious heart failure (C)</p> Signup and view all the answers

    What happens to the veins when right atrial pressure rises above their normal value?

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

    What is the normal right atrial pressure in mm Hg?

    <p>0 mm Hg (A)</p> Signup and view all the answers

    How does intra-abdominal pressure affect blood flow in the veins of the legs?

    <p>Leg veins must be at a higher pressure than abdominal pressure to open (B)</p> Signup and view all the answers

    What effect does a strong pumping action of the right heart have on right atrial pressure?

    <p>It decreases right atrial pressure. (A)</p> Signup and view all the answers

    What can contribute to increased abdominal pressure, which can affect venous return?

    <p>Excessive fluid in the abdominal cavity (C)</p> Signup and view all the answers

    Which of the following statements about the regulation of cardiac output is true?

    <p>It is influenced by both heart ability and venous return. (C)</p> Signup and view all the answers

    What happens to the right atrial pressure when peripheral venous return increases?

    <p>It increases. (A)</p> Signup and view all the answers

    What does the pressure rise in a body of water for each 13.6 millimeters of distance below the surface?

    <p>1 mm Hg (D)</p> Signup and view all the answers

    What is the typical venous pressure in the feet of an adult standing still?

    <p>+90 mm Hg (A)</p> Signup and view all the answers

    What happens to the neck veins of a person standing upright?

    <p>They collapse almost completely. (A)</p> Signup and view all the answers

    How do venous valves affect blood flow in the veins?

    <p>They ensure blood flow can only move toward the heart. (B)</p> Signup and view all the answers

    What critical function do the leg muscles serve regarding venous blood flow when a person moves?

    <p>They compress the veins and propel blood to the heart. (C)</p> Signup and view all the answers

    What is the effect of gravitational pressure on the right atrium when a person stands still?

    <p>Pressure remains about 0 mm Hg. (A)</p> Signup and view all the answers

    In which situation do the neck veins experience increased resistance?

    <p>When pressure in the veins drops below zero. (C)</p> Signup and view all the answers

    Why can't the veins inside the skull collapse?

    <p>They are protected by bone structure. (B)</p> Signup and view all the answers

    Flashcards

    Vascular Distensibility

    The ability of blood vessels to expand in response to increased pressure.

    Distensibility of Arteries vs. Veins

    Arteries are less distensible than veins, meaning they expand less for the same pressure change.

    Vein Reservoir Function

    The veins can store a significant amount of blood, acting as a reservoir for the circulatory system.

    Vascular Compliance (Capacitance)

    The ability of a vessel to accommodate a specific volume of blood for each mm Hg pressure change.

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    Distensibility

    A measure of how much a vessel expands when pressure increases.

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    Compliance vs. Distensibility

    Compliance considers the total blood storage capacity of a vascular bed at a given pressure.

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    Distensibility in the Pulmonary Circulation

    Pulmonary veins have similar distensibility to systemic veins, but pulmonary arteries are more distensible due to lower operating pressures.

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    Vein Distensibility Compared to Arteries

    Veins are about eight times more distensible than arteries, meaning a given pressure change results in a much larger volume change in veins.

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    Pulse pressure

    The pressure difference between systolic and diastolic pressure, reflecting the force of blood ejection from the heart.

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    Arterial compliance

    The ability of blood vessels to stretch and expand in response to increased pressure.

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    Stroke volume

    The amount of blood ejected from the heart with each beat.

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    Velocity of pressure pulse transmission

    The speed at which the pressure wave travels through arteries.

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    Damping of pressure pulses

    The gradual decrease in the amplitude of pressure pulses as they move away from the heart.

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    Resistance to blood movement

    Resistance to blood flow through the vessels, contributing to damping of pressure pulses.

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    Compliance of vessels

    The property of blood vessels to expand and contract, contributing to damping of pressure pulses.

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    Transmission of pressure pulses

    The process of blood vessels expanding to accommodate the increased blood flow from the heart during systole.

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    Vascular Compliance

    The property of a vessel to expand in volume in response to an increase in pressure.

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    Volume-Pressure Curve

    A graphical representation showing the relationship between pressure and volume within a blood vessel or part of the circulatory system.

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    High Compliance

    A condition where a vessel can hold a large volume of blood with only a small increase in pressure.

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    Low Compliance

    A condition where a vessel requires a significant increase in pressure to accommodate a small change in volume.

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    Sympathetic Control of Capacitance

    Sympathetic nervous system activation constricts veins, decreasing their volume and increasing pressure. This redirection of blood to the heart enhances heart pumping.

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    Sympathetic Response to Hemorrhage

    The ability of the body to maintain near-normal circulation even after significant blood loss, thanks to the vasoconstrictive ability of the sympathetic nervous system.

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    Blood Shifting to the Heart

    When vascular tone increases throughout the body, blood shifts towards the heart, enhancing cardiac output.

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    Central Venous Pressure

    This refers to the pressure within the right atrium of the heart. It's influenced by the heart's pumping ability and the inflow of blood from veins.

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    Venous Reservoir Function

    The veins can store a significant amount of blood, acting as a reservoir for the circulatory system. They can expand and contract to accommodate changes in blood volume.

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    Hydrostatic pressure in veins

    The pressure exerted by a fluid due to its weight, experienced in the vascular system as a result of blood's weight, particularly noticeable in standing individuals.

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    Collapse of neck veins

    The tendency for veins, especially in the neck, to collapse under atmospheric pressure when upright, preventing pressure from building up.

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    Venous valves

    The system of valves in veins that ensures unidirectional blood flow back to the heart, preventing backflow due to gravity.

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    Venous pump

    The mechanism by which muscle contractions squeeze blood through veins towards the heart, aided by venous valves.

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    Heart's role in venous pressure

    The pressure exerted by the heart to pump blood into arteries, counteracting the pressure build-up in the right atrium caused by gravity.

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    Right Atrial Pressure

    The pressure within the right atrium, typically ranging from -3 to -5 mmHg below atmospheric pressure. It reflects the pressure in the chest cavity surrounding the heart.

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    Intraabdominal Pressure

    The pressure in the abdominal cavity, normally around +6 mmHg but can increase to +15 to +30 mmHg due to factors like pregnancy or obesity.

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    Elevated Right Atrial Pressure

    A condition where the right atrial pressure rises above its normal value of 0 mmHg, causing blood to back up in the large veins. This leads to vein enlargement and even the opening up of collapsed veins.

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    Peripheral Venous Pressure

    The pressure in the small veins located further away from the heart, typically +4 to +6 mmHg greater than the right atrial pressure due to resistance to blood flow.

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    Vein Collapse

    The tendency of veins to become partially collapsed into an ovoid or slit-like shape, particularly in the abdomen due to compression from organs and internal pressure.

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    Veins as Blood Reservoirs

    Veins serve as a blood reservoir, capable of holding significant amounts of blood. This allows for a rapid increase in blood volume in the circulation when needed.

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    Leg Vein Pressure and Intraabdominal Pressure

    When intraabdominal pressure rises, the pressure in the veins of the legs must exceed the abdominal pressure to enable blood flow from the legs to the heart.

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    Femoral Vein Pressure

    The pressure in the femoral veins, which is generally equal to or slightly higher than the intraabdominal pressure due to the need to overcome the abdominal pressure for blood flow.

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    Study Notes

    Vascular Distensibility and Functions

    • Blood vessels are distensible, meaning they can stretch.
    • Arteries accommodate the heart's pulsatile output, smoothing blood flow.
    • Veins are highly distensible, acting as reservoirs for extra blood. A rise in venous pressure causes a significant volume increase (0.5-1.0 liters).
    • Vascular distensibility is the fractional increase in volume per mm Hg rise in pressure.

    Vascular Distensibility Formula/Calculation

    • Vascular distensibility = (Increase in volume) / (Increase in pressure × Original volume)
    • Example: If a 10 ml vessel increases by 1 ml with a 1 mm Hg increase, distensibility is 0.1 per mm Hg or 10% per mm Hg.

    Arteries and Veins: Distensibility Comparison

    • Arteries are stronger than veins.
    • Veins are roughly eight times more distensible than arteries.
    • A given pressure increase causes more blood volume increase in veins than in arteries of similar size.

    Compliance or Capacitance

    • Compliance (or capacitance) is more important than distensibility in hemodynamic studies.
    • It measures the total blood volume a part of the circulation can hold for a given pressure increase.
    • Vascular compliance = (Increase in volume) / (Increase in pressure)
    • Compliance and distensibility are not the same; compliance is equal to distensibility times volume.
      • A highly distensible vessel with a small volume has potentially lower compliance than a less distensible vessel with a larger volume.
    • Compliance for Systemic Veins
      • Systemic veins are 24 times more compliant than corresponding arteries. This high compliance is due to both an eight-fold increase in distensibility and a three-fold increase in volume.

    Volume-Pressure Curves

    • Reflect the relationship between volume and pressure in blood vessels.
    • The arterial system in an average adult, holding 700ml of blood at a mean arterial pressure of 100mm Hg, falls to zero when the volume decreases to 400ml.
    • The venous system has a volume range of 2000-3500ml and a pressure change from 3-5mm Hg.
    • Sympathetic stimulation leads to increased vascular smooth muscle tone and pressure at each volume. Inhibiting the same causes a lowering of pressure.
    • Changes in vascular tone shifts blood volume to different segments of the circulation.
    • Blood shift to the heart is one of the primary methods to increase cardiac output
    • Vascular tone changes, particularly in veins, maintain circulation even with large blood loss

    Delayed Compliance

    • Delayed Compliance: A vessel initially displays a large pressure increase with rising volume. But the pressure eventually returns to a normal level over several minutes or hours due to gradual smooth muscle stretching.
    • Increased blood volume results in a large initial pressure increase.
    • The pressure subsequently decreases, returning to normal levels over time due to delayed smooth muscle adaptation.
    • Immediate stretching of the vessel in response to volume expansion is followed by a delayed effect of increasing tensile strength in the vessel.

    Arterial Pressure Pulsations

    • Each heartbeat injects blood. Inertia initially restricts movement, causing proximal aorta stretching.

    • Distention spreads progressively, transmitting the pressure pulse throughout the artery.

    • Compliance minimizes pressure fluctuations in the smaller vessels, leading to continuous tissue blood supply.

    • Normal systolic pressure in young adults is around 120 mm Hg. Diastolic pressure is roughly 80 mm Hg. Pulse pressure is 40mm Hg (120-80)

    • Age and arterial hardening (arteriosclerosis) impacts pulse pressure through lowered compliance

    Transmission of Pressure Pulses

    • The velocity of pressure wave movement depends upon the compliance of the vessels.
    • Arterial compliance is a significant factor in transmitting pressure waves with the speed influenced by the resistance of the vessel and vessels’ compliance.
    • Damping of pressure waves is due to resistance of the vessels and compliance. The more compliant a vessel, the more blood required for a pressure increase.

    Veins and Their Functions

    • Veins can constrict or enlarge to hold more/less blood, making blood available when necessary.
    • Peripheral veins regulate cardiac output by acting as a venous pump.
    • The pressure in the right atrium (central venous pressure) relies on heart pumping ability and the flow of blood from peripheral veins.
    • The right atrial pressure decreases with stronger heart pumping, conversely weak heart pumping increases right atrial pressure. Blood entering the right atrium from peripheral veins also increases pressure.
    • Several factors influence venous return (increased blood volume, vascular tone, and arteriolar dilation)

    Specific Blood Reservoirs

    • Selected vascular regions (e.g., spleen, liver, abdominal veins, subcutaneous veins) function as reservoirs to regulate blood volume by storing or releasing different blood volumes.
    • The heart and lungs, although not directly parts of the systemic venous system, can also act as blood reservoirs, expanding or shrinking to accommodate blood demands.

    Venous Valves and the "Venous Pump"

    • Valves in veins prevent backflow.
    • Leg muscle contractions are crucial to venous return.
    • The muscle pump or venous pump efficiently returns blood against gravity in standing positions or exertion.
    • The gravitational effects on venous pressure within the lower body will cause an increase to 90 mm Hg if a person is standing completely still for 30 seconds.

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    Vascular Distensibility and Functions PDF

    Description

    This quiz explores the intricate relationships between compliance, distensibility, and volume in blood vessels. It focuses on the differences between systemic veins and arteries, the effects of sympathetic stimulation, and how the body responds to changes in vascular tone during different physiological conditions.

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