Heart 9

Question 1

Central venous pool

Answer 1

corresponds approximately to the volume enclosed by the right atrium and the great veins in the thorax

Question 2

Venous return

Answer 2

Rate at which blood returns to the thorax from the peripheral vascular beds, i.e. blood entering the central venous pool

Question 3

Cardiac output

Answer 3

Rate at which blood leaves the central venous pool and is pumped out of the heart

Question 4

Norma stead-state conditions

Answer 4

Venous return = cardiac output

Question 5

Mean circulatory pressure

Answer 5

Mean pressure that exists in the circulatory system when cardiac output stops and the pressures within the vascular system redistribute

Question 6

What does Pmc represent?

Answer 6

Relationship between the volume of blood in circulation compared to the functional capacity of the system

Question 7

By what is Pmc influenced?

Answer 7

Volume of circulating blood and the smooth muscle venous tone

Question 8

Pmc is normally . . .

Answer 8

7 mmHg

Question 9

When central venous pressure equals mean circulatory pressure, . . .

Answer 9

there is no pressure gradient for venous return (blood flow ceases)

Question 10

With normal heart function, and increase in cardiac output . . .

Answer 10

decreases CVP and increases the pressure gradient for venous return (increases venous return)

Question 11

What happens at negative CVP?

Answer 11

Transmural pressure collapses the large veins, resulting in zero venous return

Question 12

Four things that will influence venous return

Answer 12

Peripheral venous pressure, central venous pressure, venous valves, cardiac contraction

Question 13

What would increase peripheral venous pressure?

Answer 13

• Increased sympathetic venoconstriction
• Increased blood volume
• Increased skeletal leg muscle pumping activity

Question 14

What would decrease central venous pressure?

Answer 14

Respiratory pump activity

Cardiac suction

Question 15

How do venous valves help regulate venous return?

Answer 15

Maintains pressure gradient between peripheral and central venous pools in the face of gravitational forces

Question 16

How does cardiac contraction help regulate venous pressure?

Answer 16

Contractions generate peripheral venous pressure

Question 17

How would hemorrhage or decreased venous tone change the vascular function curve?

Answer 17

Parallel shift down and to the left

Question 18

How would transfusion or increased venous tone affect the vascular function curve?

Answer 18

Parallel shift up and to the right

Question 19

Any shift in the vascular function curve will also change what?

Answer 19

Mean systemic circulatory pressure

Question 20

Factors that influence the level of cardiac function and shift the cardiac function curve

Answer 20

• Sympathetic stimulation (elevates cardiac function curve)
• Inotropic drugs
• Heart failure (depresses cardiac function curve)

Question 21

How do kidneys respond to decreased cardiac output?

Answer 21

By increasing blood volume (fluid retention)

Question 22

When does fluid retention become an issue?

Answer 22

In severe heart failure, the heart’s contractility is reduced so much that cardiac output cannot be maintained, even with very elevated CVP.

Question 23

What other problems does CHF cause?

Answer 23

Pulmonary congestion and pitting edema of the extremities.

Question 24

After hemorrhage, several adaptive changes occur acutely. What are they?

Answer 24

Venoconstriction, arterial vasoconstriction, increased cardiac contractility

Question 25

Why do post-hemorrhagic adaptive changes occur?

Answer 25

The low blood pressure in the capillaries shift the equilibrium of hydrostatic and oncotic pressures, resulting in net reabsorption of fluid from the tissues, partially restoring lost blood volume

Question 26

Maximum survivable blood loss

Answer 26

40% of total blood volume (approximately 2 L)

Question 27

Long-term post-hemorrhagic adaptive responses

Answer 27

Increased salt and water retention by the kidneys to increase blood volume, increased red blood cell synthesis to restore the blood’s oxygen carrying capacity