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?

Several hundred milliliters Signup and view all the answers

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

It increases the pressure at each volume. Signup and view all the answers

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

Shifting large volumes of blood into the heart. Signup and view all the answers

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

It constricts vessel sizes to maintain circulation. Signup and view all the answers

What volume range does the systemic venous system typically contain?

2000 to 3500 milliliters Signup and view all the answers

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

To allow smooth, continuous blood flow Signup and view all the answers

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

Veins are about eight times more distensible than arteries Signup and view all the answers

What defines vascular compliance or capacitance?

The total blood volume stored per mm Hg pressure increase Signup and view all the answers

What is expressed by the formula for vascular distensibility?

The fractional increase in volume per mm Hg rise in pressure Signup and view all the answers

Which statement accurately describes pulmonary circulation compared to systemic circulation?

Pulmonary arteries have greater distensibility than systemic arteries Signup and view all the answers

What happens to veins during slight increases in venous pressure?

They store an additional 0.5 to 1.0 liter of blood Signup and view all the answers

Why is compliance more important than distensibility in hemodynamic studies?

It shows the total blood volume that can be stored at a certain pressure 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?

0.1 per mm Hg Signup and view all the answers

What primarily determines pulse pressure?

Stroke volume output and arterial compliance Signup and view all the answers

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

Pulse pressure can increase to twice normal Signup and view all the answers

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

3 to 5 m/sec Signup and view all the answers

What two factors contribute to the damping of pressure pulses?

Resistance to blood movement and compliance of the vessels Signup and view all the answers

How does increased arterial resistance impact pulse pressure?

It reduces pulse pressure Signup and view all the answers

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

Increased compliance slows down pulse transmission Signup and view all the answers

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

Inertia of the blood Signup and view all the answers

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

Higher stroke volume typically results in higher pulse pressure if compliance is low Signup and view all the answers

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

-3 to -5 mm Hg Signup and view all the answers

What causes the right atrial pressure to approach lower values?

Severe hemorrhage Signup and view all the answers

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

It dampens the pulsations of pressure. Signup and view all the answers

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

When right atrial pressure rises above +4 to +6 mm Hg Signup and view all the answers

What physiological mechanism allows veins to propel blood forward?

Venous pump 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?

About +4 to +6 mm Hg greater Signup and view all the answers

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

Decreased large vessel tone Signup and view all the answers

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

Pregnancy Signup and view all the answers

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

Serious heart failure Signup and view all the answers

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

They enlarge and collapse points open Signup and view all the answers

What is the normal right atrial pressure in mm Hg?

0 mm Hg Signup and view all the answers

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

Leg veins must be at a higher pressure than abdominal pressure to open Signup and view all the answers

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

It decreases right atrial pressure. Signup and view all the answers

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

Excessive fluid in the abdominal cavity Signup and view all the answers

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

It is influenced by both heart ability and venous return. Signup and view all the answers

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

It increases. 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?

1 mm Hg Signup and view all the answers

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

+90 mm Hg Signup and view all the answers

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

They collapse almost completely. Signup and view all the answers

How do venous valves affect blood flow in the veins?

They ensure blood flow can only move toward the heart. Signup and view all the answers

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

They compress the veins and propel blood to the heart. Signup and view all the answers

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

Pressure remains about 0 mm Hg. Signup and view all the answers

In which situation do the neck veins experience increased resistance?

When pressure in the veins drops below zero. Signup and view all the answers

Why can't the veins inside the skull collapse?

They are protected by bone structure. Signup and view all the answers

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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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.