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Physiology > Cardiac Output > Flashcards

Cardiac Output Flashcards

1
Q

What is occurring during the ST segment?

A

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

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2
Q

What causes the RAD with a RBBB?

A

Negative vector in lead III

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3
Q

What is cardiac output?

A

HR x SV

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4
Q

What is stroke volume?

A

LVEDV -LVESV

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5
Q

What are the four factors that affect cardiac output?

A
  1. Preload
  2. Contractility
  3. Afterload
  4. HR
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6
Q

What is preload?

A

end diastolic pressure

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7
Q

What is afterload?

A

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

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8
Q

What is the Frank-Starling mechanism of the heart?

A

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)

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9
Q

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

A

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

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10
Q

How is CO maintained when HR decreases?

A

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

(CO = HR x SV)

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11
Q

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

A

Blood is filling the ventricle

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12
Q

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

A

Isovolumic contraction

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13
Q

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

A

The left ventricular end-diastolic volume

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14
Q

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

A

Semi-lunar valve opens, starting the ejection phase

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15
Q

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

A

Ejection of blood

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16
Q

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

A

Aortic valve closes

Isovolumic relaxation begins

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17
Q

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

A

AV valves open

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18
Q

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

A

Increases it

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19
Q

Increasing afterload does what to stroke volume?

A

Decreases it

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20
Q

What is the clinical correlation to afterload?

A

HTN

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21
Q

What did Sarnoff contribute?

A

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

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

22
Q

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

A

Shifts curve upward, causing increase in CO

23
Q

What are three causes of decreased contractility?

A

MI
Volume overload
Dilated cardiomyopathy

24
Q

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

A

Lower CO

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

25
Q

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

A

Hypertrophy
Remodeling of the matrix
Transient ischemia

26
Q

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

A

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

27
Q

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

A

Atrial pressure = venous pressure, meaning no flow of blood

28
Q

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

A

Shifts downward at every point of atrial pressure

29
Q

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

A

Shifts upward at every point of atrial pressure

30
Q

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

A

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

31
Q

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

A

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

32
Q

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

A

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

33
Q

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

A

Increases CO d/t an increase in the SV

34
Q

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

A

Lower HR, decreases CO at every point of RA pressure

35
Q

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

A

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

36
Q

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

A

Lower HR, decreases CO at every point of RA pressure

37
Q

How does the SNS increase the force of heart contraction?

A

Changes the Ca permeability of the myocytes,

38
Q

How does the PNS decrease the heart rate?

A

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

39
Q

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

A

Increased glycogenolysis

Increased cellular permeability to calcium, making muscles contract more easily

40
Q

What happens during diastole when the SNS tone increases?

A

Enhanced Ca uptake (sequestration and efflux)

This decreases the time the heart spends in diastole, and makes the heart more efficient

41
Q

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

A

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

42
Q

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

A

The point where inflow matches outflow

43
Q

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

A

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

44
Q

What is the effect of an AV shunt on CO?

A

Reduced peripheral resistance, increasing CO

45
Q

What is the effect of hyperthyroidism on CO?

A

Increase CO

46
Q

What is the effect on anemia on CO?

A

Increases

47
Q

What is the effect of heart damage on CO?

A

decrease

48
Q

What is the effect of decreased blood volume on CO?

A

Decreases

49
Q

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

A

Decreases CO (impedes what is coming back)

50
Q

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

A

Decreases CO

Physiology (75 decks)

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