Crr Week 3: Cardiac Output And Venous Return (Dormer)

Front 1

What is the normal pressure gradient between peripheral and central veins?

Back 1

~15 mmHg

Front 2

How does increased metabolism affect the cardiac output?

Back 2

Leads to decreased vascular resistance (vasodilation) which increases venous return and increases cardiac output

Front 3

What happens to RAP if venous return exceeds cardiac output?

Back 3

Right atrial pressure (RAP) will increase

Front 4

What is the normal central venous pressure (CVP)?

Back 4

2-4 mmHg

Front 5

On the vascular function curve, as "pump flow" increases, what happens to RAP?

Back 5

RAP decreases

Front 6

What is the effect of changing blood volume on the vascular function curve (what kind of shifts take place)?

Is there a change in the mean circulatory filling pressure?

Back 6

Increases or decreases in blood volume will cause a parallel shift in the vascular function curve

The Mean circulatory filling pressure would increase or decrease based on the increase/decrease of blood volume

Front 7

What is the effect of changing vascular tone (compliance) on the vascular function curve?

Back 7

Changing vascular tone results in the same shifts as changing blood volumes

Both result in parallel shifts

Front 8

What is the effect of vasoconstriction/vasodilation on the vascular function curve

Is there a change in the mean circulatory filling pressure?

Back 8

The curve shifts up or down in a non-parallel manner.

There is NO change in Mean circulatory filling pressure

Front 9

If the pump were kept constant, how would RAP change with vasoconstriction and vasodilation?

Back 9

RAP would increase with vasodilation and decrease with vasoconstriction

Front 10

What is the intersection of the cardiac function curve and the vascular function curve and what does it represent?

Back 10

Equilibrium point
(steady state condition)

Front 11

What is the Bainbridge reflex?

Back 11

Reflex tachycardia resulting from a sudden, transient increase in RAP

Front 12

As cardiac output increases, RAP ________ (increases/decreases)?

Back 12

Increases

Front 13

How would a transfusion shift the vascular function curve?

Back 13

Shift to the right

Front 14

How would hemorrhaging shift the vascular function curve?

Back 14

Shift to the left

Front 15

How do cardiac glycosides, such as digitalis, shift the cardiac function curve?

Back 15

Up and to the left
(establishes new steady state and equilibrium point)

Front 16

What is the effect of cardiac glycosides on cardiac output and RAP?

Back 16

Higher cardiac output, lower RAP
(shifts up and to the left)

Front 17

When total peripheral resistance is increased, what happens to the equilibrium point?

Back 17

Shifts down

*With increased TPR, there is a decrease in CVP (less blood in the venous compartment), so the venous function moves downward. With less venous return, the heart is less effective as a pump and so the cardiac function shifts downward.

Front 18

What does the vascular function graph plot?

Back 18

Right atrial pressure vs. venous return

Front 19

Why does the right atrial pressure increase as venous return decreases?

Back 19

When venous return decreases, the pressure gradient (driving force) between peripheral blood pressure and CVP decreases. To decrease this pressure gradient, RAP must increase.

Front 20

Define the mean systemic pressure?

Back 20

Value for right atrial pressure at which venous return is zero.
(point at which vascular function curve intersects the x-axis)

*This is the pressure that would be measured throughout the cardiovascular system if the heart were stopped.
(Pressure would be the same throughout the vasculature, and would be equal to the mean systemic pressure.

When pressures are equal throughout the vasculature, there is no blood flow, and therefore venous return is zero

Front 21

As the right atrial pressure increases, does the driving force (pressure gradient) in the vasculature increase or decrease?

Back 21

The driving force decreases

Front 22

Which 2 factors influence the value for mean systemic pressure?

Back 22

1. Blood volume
2. Distribution of blood between the unstressed volume (veins) and the stressed volume (arteries)

Front 23

When blood volume increases, what happens to the mean systemic pressure?

Back 23

Mean systemic pressure increases
(vascular function shifts to the right)

Front 24

Increased blood volume and ________(increased/decreased) compliance of the veins produces an __________ in the mean systemic pressure and shift the vascular function curve to the _________.

Back 24

Increased blood volume, decreased compliance
*Shift vasculature curve to the right

Front 25

What is the slope of the vasculature curve deteremined by?

Back 25

Total peripheral resistance (TPR)

Front 26

How does decreased peripheral resistance affect the vascular function curve?

Back 26

Decreased TRP shifts the curve CLOCKWISE
(For a given atrial pressure, venous return is increased (vasodilation))

Front 27

How does increased peripheral resistance affect the vascular function curve?

Back 27

Increased TPR shifts the curve counterclockwise
(For a given atrial pressure, venous return is less (vasoconstriction))

Front 28

At the equilibrium point, the system is in "steady state." What does this mean?

Back 28

Cardiac output and venous return are, by definition, equal at the point of intersection

Front 29

How does a high right atrial pressure increase stroke volume and cardiac output?

Back 29

As the right atrial pressure and EDV are increased, there is increased ventricular fiber length, which leads to increased stroke volume and cardiac output

*The higher the right atrial pressure, the higher the cardiac output
(Frank-Starling relationship)

Front 30

As right atrial pressure decreases, why does venous return increase?

Back 30

There is a higher pressure gradient (greater driving force)

Front 31

List 3 types of mechanisms that can change the cardiac output.

Back 31

1. Positive or negative inotropic effects (contractility)
2. Changes in blood volume or venous compliance
3. Changes in TPR

Front 32

Which curve is affected by positive inotropic agents, and what is the effect?

Back 32

Cardiac function curve is affected
Increased contractility shifts the curve up and to the left

Front 33

What happens to cardiac output and right atrial pressure when a positive inotropic agent is administered?

Back 33

The cardiac output increases and the right atrial pressure decreases
(cardiac function curve shifts upward and to the left)

Front 34

When blood volume is increased or decreased, why is there a parallel shift in the vascular function curve?

Back 34

The shift is parallel (no change in slope) because the TPR remains constant.

Front 35

What is the effect of increased resistance on the cardiac function curve?

Back 35

Increased resistance causes and increased afterload and a decreased cardiac output.

*This shifts the curve DOWNWARD as a result of the decreased afterload

Front 36

Why is the venous function curve shifted downward when TPR is increased?

Back 36

Less venous return