Cardiac Output

Question 1

What is occurring during the ST segment?

Answer 1

Ca and K channels are open, allowing for the plateau phase

Question 2

What causes the RAD with a RBBB?

Answer 2

Negative vector in lead III

Question 3

What is cardiac output?

Answer 3

HR x SV

Question 4

What is stroke volume?

Answer 4

LVEDV -LVESV

Question 5

What are the four factors that affect cardiac output?

Answer 5

1. Preload
2. Contractility
3. Afterload
4. HR

Question 6

What is preload?

Answer 6

end diastolic pressure

Question 7

What is afterload?

Answer 7

The pressure in the aorta leading from the ventricle (aortic pressure). It is related to total peripheral resistance

Question 8

What is the Frank-Starling mechanism of the heart?

Answer 8

As the end diastolic volume of the heart increases, the systolic pressure increases

(i.e. the greater the heart muscle is stretched during filling, the greater is the force of contraction and the greater the quantity of blood pumped into the aorta)

Question 9

What is the consequence of the Frank-Starling mechanism of the heart?

Answer 9

Venous return directly influences systolic pressure, up to a point, after which heart failure occurs

Question 10

How is CO maintained when HR decreases?

Answer 10

Decreased HR will increase the SV d/t higher EDSV. Vice versa holds as well.

(CO = HR x SV)

Question 11

What is occurring in phase 1 of the pressure-volume diagram?

Answer 11

Blood is filling the ventricle

Question 12

What happens at point B of the pressure-volume diagram?

Answer 12

Isovolumic contraction

Question 13

What does the point B of of the pressure-volume diagram correspond to?

Answer 13

The left ventricular end-diastolic volume

Question 14

What is occurring at point c of the pressure-volume diagram?

Answer 14

Semi-lunar valve opens, starting the ejection phase

Question 15

What is occurring at the top line of the pressure-volume diagram?

Answer 15

Ejection of blood

Question 16

What is occurring at point D of the pressure-volume diagram? What phase of the heart cycle begins at this point?

Answer 16

Aortic valve closes

Isovolumic relaxation begins

Question 17

What is occurring at point A of the pressure-volume diagram?

Answer 17

AV valves open

Question 18

Increasing the end diastolic volume (increasing preload) does what to stroke volume?

Answer 18

Increases it

Question 19

Increasing afterload does what to stroke volume?

Answer 19

Decreases it

Question 20

What is the clinical correlation to afterload?

Answer 20

HTN

Question 21

What did Sarnoff contribute?

Answer 21

Showed the effect of heart contractility on HR, SV, and CO

shift of the curve, rather than a shift along the curve

Question 22

What will happen to the afterload curve, if contractility of the heart increases? What is the effect of CO?

Answer 22

Shifts curve upward, causing increase in CO

Question 23

What are three causes of decreased contractility?

Answer 23

MI
Volume overload
Dilated cardiomyopathy

Question 24

What will happen if the heart cannot relax as efficiently? How is this reflected in the graph?

Answer 24

Lower CO

Shift the end diastolic pressure curve upward at every point of volume

Question 25

What can cause an upward shift in the end diastolic pressure curve?

Answer 25

Hypertrophy Remodeling of the matrix Transient ischemia

Question 26

What causes the plateau of the frank-starling law of the heart curve?

Answer 26

Collapse of the large veins under high negative pressure in the chest

Question 27

What happens at the x intercept of the frank starling curve?

Answer 27

Atrial pressure = venous pressure, meaning no flow of blood

Question 28

What happens to the venous return curve if you lose blood?

Answer 28

Shifts downward at every point of atrial pressure

Question 29

What happens to the venous return curve if you gain blood?

Answer 29

Shifts upward at every point of atrial pressure

Question 30

What happens to the venous return curve if you constrict your veins?

Answer 30

Shifts curve downward (decrease the amount of blood returned to the right atrium at every level of right atrial pressure)

Question 31

What happens to the venous return curve if you dilate your veins?

Answer 31

Shifts curve upward (increase the amount of blood returned to the right atrium at every level of right atrial pressure)

Question 32

Vasocontriction or vasodilation will change the Psf (mean systemic pressure) how?

Answer 32

No change (there is no change in blood volume, just how it is distributed)

Question 33

As right atrial pressure increases, what is the effect on CO? How does it bring about this effect?

Answer 33

Increases CO d/t an increase in the SV

Question 34

How does the PNS exert its effects? How is this reflected on the cardiaic output/right atrial pressure curve?

Answer 34

Lower HR, decreases CO at every point of RA pressure

Question 35

How does the SNS exert its effects? How is this reflected on the cardiaic output/right atrial pressure curve?

Answer 35

Increases HR and contractility of the heart, increasing the CO at every point or RA pressure

Question 36

How does SNS withdrawl exert its effects? How is this reflected on the cardiaic output/right atrial pressure curve?

Answer 36

Lower HR, decreases CO at every point of RA pressure

Question 37

How does the SNS increase the force of heart contraction?

Answer 37

Changes the Ca permeability of the myocytes,

Question 38

How does the PNS decrease the heart rate?

Answer 38

Increases K permeability to increase the phase 4 depolarization of the SA node

Question 39

What are the two changes in systole that bring about the effects of increased sympathetic tone during exercise?

Answer 39

Increased glycogenolysis | Increased cellular permeability to calcium, making muscles contract more easily

Question 40

What happens during diastole when the SNS tone increases?

Answer 40

Enhanced Ca uptake (sequestration and efflux) This decreases the time the heart spends in diastole, and makes the heart more efficient

Question 41

Why does increase Ca reuptake and sequestration increase heart efficiency during exercise?

Answer 41

Lowers the amount of time that is needed to prepare the Ca for release during the next heart cycle.

Question 42

What does the eqilibrium point on the cardiac output/venous return point represent?

Answer 42

The point where inflow matches outflow

Question 43

What is the Fick's principle of measuring cardiac output?

Answer 43

Recording the amount of oxygen absorbed by the blood compared to how much returns

Question 44

What is the effect of an AV shunt on CO?

Answer 44

Reduced peripheral resistance, increasing CO

Question 45

What is the effect of hyperthyroidism on CO?

Answer 45

Increase CO

Question 46

What is the effect on anemia on CO?

Answer 46

Increases

Question 47

What is the effect of heart damage on CO?

Answer 47

decrease

Question 48

What is the effect of decreased blood volume on CO?

Answer 48

Decreases

Question 49

What is the effect of acute venous dilation or venous obstruction?

Answer 49

Decreases CO (impedes what is coming back)

Question 50

What is the effect of decreased tissue mass or tissue metabolism on CO?

Answer 50

Decreases CO