20 Cardiac output

Question 1

Is the SV of right ventricle = left ventricle?

Answer 1

Yes

Question 2

What is the equation to Cardiac Output?

What is the typical value of CO?

Answer 2

CO = HR x SV

5L/min

Question 3

What are the main sympathetic and parasympathetic receptors that control heart rate and contractility?
What are their effects?

Answer 3

Sym: B1 receptors, positive peffect

Para sym: M2 receptors, negative effect

Question 4

How do an increase in preload and afterload affect contractility?

Answer 4

Preload: increase contractility due to increased cardiomyocyte stretching, thus more shortening

Afterload: decrease contractility as more blood in aorta, ventricle is harder to contract to produce the same force

Question 5

What is EDV determined by?

Answer 5

Preload/ venous return

Question 6

What does the intersection of cardiac function curve and the vascular function curve shows?

Answer 6

The cardiac output (draw a line to the y axis)

Question 7

What is the effect on the cardiac function curve and vascular function curve if there is an increase in contractility?

Answer 7

Cardiac function curve: moves upward

Vascular function curve: unchanged

Question 8

What is the effect on the cardiac function curve and vascular function curve if there is an increase in blood volume?

Answer 8

Cardiac function curve:
unchanged (relationship between atrial pressure and CO is the same)

Vascular function curve: shift right parallel

• increase in volume affects venous return at all pressures
• decrease in venous compliance

Question 9

What can increase venous return?

A. Respiration
B. Skeletal muscle pump
C. Sympathetic activity 
D. Systolic blood pressure
E. Cardiac suction effect
F. Venous valves
G. Blood volume

Answer 9

All except D
D: depends on vascular resistance

C: increase sympathetic vasoconstriction activity can increase venous pressure

Question 10

What does area within the P-V loop represents?

Answer 10

Stroke work

= Stroke volume x aortic pressure

Question 11

What is cardiac minute work?

What does it correlates with?

Answer 11

CO x aortic pressure ;

Myocardial oxygen consumption

Question 12

____ of myocardial O2 consumed in basal
metabolism.
____ of myocardial O2 consumed in ________.

Answer 12

25%;
75%
ATP production for contraction

Most of it is spent in isovolumetric contraction.

Question 13

What is the Fick principle in cardiac output determination?

Answer 13

body O2 consumption (expressed as
consumption rate) is equal to the difference between O2 delivered via
pulmonary vein (to left atrium) and O2 delivered via pulmonary artery (from right ventricle)