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A&P2 Spring 25’ > 21 Jan 25 Understanding CO and the CV System Mechanically > Flashcards

21 Jan 25 Understanding CO and the CV System Mechanically Flashcards

1
Q

What is the Reynolds number?

A

A hypothetical number that is completely unitless

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2
Q

What does a Reynolds number greater than 2000 indicate?

A

Turbulent flow

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3
Q

What is turbulent flow characterized by?

A

Blood moving in all different directions, mass amounts of energy wasted, and risk for clotting

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4
Q

What can cause hardened arteries or plaque deposits?

A

Turbulent flow associated with narrowing of blood vessels

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5
Q

What is the equation for Reynolds number?

A

RE = (V x D x P) ÷ h

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6
Q

What does ‘V’ represent in the Reynolds number equation?

A

Velocity

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7
Q

What does ‘D’ represent in the Reynolds number equation?

A

Diameter

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8
Q

What does ‘P’ represent in the Reynolds number equation?

A

Density

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9
Q

What does ‘h’ represent in the Reynolds number equation?

A

Viscosity

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10
Q

Which blood vessels are most prone to turbulent flow?

A

Large arteries close to the heart, such as the Aorta

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11
Q

True or False: The venous side of circulation typically experiences turbulent flow.

A

False

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12
Q

How does the pressure change in the arterial system compared to the venous system when volume changes?

A

Pressure changes a lot in the arterial system when volume changes a little, indicating low compliance

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13
Q

What happens to pressure in the veins when volume is added or removed?

A

Pressure only changes a little, indicating high compliance

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14
Q

What effect does removing sympathetic stimulation have on arteries and veins?

A

Pressure in both decreases, but it decreases faster in arteries

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15
Q

What is the primary method for measuring blood flow?

A

Using flow meters, such as electromagnetic or ultrasonic flow meters

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16
Q

What does the pressure-volume loop analyze?

A

The different pressures and volumes in the chambers of the heart during the cardiac cycle

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17
Q

What is the end systolic volume (ESV) in a healthy heart after filling?

A

50 mls

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18
Q

What is the primary mode of filling in the heart?

A

Passive filling

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19
Q

What is the role of atrial contraction in ventricular filling?

A

Provides a small additional volume of blood to the ventricle right before contraction

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20
Q

Fill in the blank: The atrial contribution to filling becomes very important in cases of _______.

A

[heart pathology]

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21
Q

What happens to the atria in healthy individuals during the pumping and filling process?

A

The atria aren’t necessary; passive filling can occur via pulmonary veins.

Healthy individuals can achieve ventricular filling without atrial contraction.

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22
Q

What is the atrial kick and its significance in heart failure?

A

In heart failure, the atrial contraction may contribute about 25% or more to ventricular volume.

Healthy individuals do not rely on atrial contraction for ventricular filling.

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23
Q

What is diastole?

A

Diastole is the phase of filling in the cardiac cycle.

It begins when the ventricles are relaxed and blood fills the chambers.

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24
Q

What occurs at the end of diastole in the cardiac cycle?

A

The ventricle starts to contract.

This transition marks the end of phase one.

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25
Q

Describe phase two of the cardiac cycle.

A

In phase two, the heart contracts, increasing left ventricular pressure, forcing the mitral valve to close.

Both the aortic and mitral valves should be closed during this phase.

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26
Q

What is isovolumetric contraction?

A

It is the phase where the ventricles contract with both valves closed, resulting in no change in volume.

This phase is represented by a vertical line on the pressure-volume graph.

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27
Q

What defines the period of ejection in the cardiac cycle?

A

It occurs when left ventricular pressure exceeds aortic pressure, opening the aortic valve.

This happens during phase three.

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28
Q

How is stroke volume calculated?

A

Stroke volume is the difference between left ventricular end diastolic volume and left ventricular end systolic volume.

Example: 120 mL (EDV) - 50 mL (ESV) = 70 mL (SV).

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29
Q

What starts phase four of the cardiac cycle?

A

Phase four begins when the aortic valve closes and the mitral valve remains closed.

This phase is known as isovolumetric relaxation.

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30
Q

When does diastole officially start?

A

Diastole starts when the aortic valve closes, marking the end of phase three.

It continues until the start of phase two.

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31
Q

What is the role of pressure during the filling phase?

A

Ventricular pressure is very low during filling, increasing significantly during ejection.

Atrial contraction causes a slight increase in pressure during this phase.

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32
Q

What is the relationship between electrical events and pressure changes in the heart?

A

Electrical events, like depolarization, occur before changes in ventricular pressure.

This delay is due to the time it takes for calcium to bind and generate force.

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33
Q

How does the pressure-volume loop relate to the strength of the heart’s contraction?

A

The position of the pressure-volume loop indicates the contractile state of the heart.

Stronger contractions generate higher pressures, shifting the loop’s position.

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34
Q

What happens to left ventricular volume during phases 1 and 3?

A

Volume increases during phase 1 (filling) and decreases during phase 3 (ejection).

The volume change is significant in assessing cardiac function.

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35
Q

In what part of phase one does rapid filling occur?

A

Rapid filling occurs in the first third of phase one when the mitral valve opens.

Blood from the left atrium floods into the ventricle quickly.

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36
Q

What occurs when the mitral valve opens?

A

Blood floods into the ventricle very quickly

This represents the phase of rapid filling during the cardiac cycle.

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37
Q

What are the three parts of Phase 1 filling?

A
  • Rapid filling
  • Middle third (not much happening)
  • End of phase with a little extra volume from the atria
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38
Q

How does a stenotic mitral valve affect ventricular filling?

A

Filling occurs slower due to impedance from the left atria to the left ventricle.

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39
Q

What happens to cardiac output during tachycardia with a bad mitral valve?

A

Cardiac output becomes a problem due to insufficient filling time.

40
Q

What is the volume in the ventricle right before the aortic valve opens?

A

120 cc’s

41
Q

What happens to ventricular volume during systole?

A

Volume decreases from 120 cc’s to about 50 cc’s, ejecting 70 cc’s.

42
Q

True or False: Ejection stops at the peak of aortic pressure.

A

False

43
Q

What is isovolumetric contraction?

A

Pressure increases without volume change, occurring during Phase II.

44
Q

What correlates with the first heart sound?

A

AV valves closing

45
Q

What correlates with the second heart sound?

A

Aortic valve closing

46
Q

What is the expected pressure in the atria during contraction?

A

Atrial pressure increases.

47
Q

Fill in the blank: The mitral valve is also known as the _______.

A

bicuspid valve

48
Q

What is depicted in a Carl J. Wiggers diagram?

A

Various cardiac variables plotted over time.

49
Q

What happens at a right atrial pressure of zero?

A

Normal cardiac output is about 5L/min.

50
Q

What must happen for cardiac output to be sustained?

A

Blood must return to the heart.

51
Q

What is the relationship between right atrial pressure and venous return?

A

Elevated right atrial pressure indicates elevated venous return.

52
Q

What is the primary determinant of whether the heart can maintain cardiac output?

A

The health and efficiency of the heart’s pumping ability.

53
Q

What is the normal venous return rate to the heart?

A

5 L/min

54
Q

What happens to venous return if right atrial pressure is higher than zero?

A

Lower venous return

55
Q

What is the relationship between venous return and cardiac output?

A

Cardiac output depends on venous return

56
Q

What defines the flow in the cardiovascular system?

A

Delta P (pressure difference)

57
Q

At what right atrial pressure does normal venous return occur?

A

Zero mmHg

58
Q

What effect does a lower than normal right atrial pressure have on venous return?

A

Increases venous return

59
Q

What is the mean systemic filling pressure (PSF) in mmHg?

A

7 mmHg

60
Q

What happens to venous return if the right atrial pressure is significantly lower than normal?

A

Veins may collapse, limiting augmentation of venous return

61
Q

What is the typical maximum venous return rate under normal conditions?

A

About 6 L/min

62
Q

How does resistance to venous return affect blood flow back to the heart?

A

Higher resistance impedes venous return

63
Q

What two factors primarily affect systemic filling pressure?

A
  • Blood volume
  • Venous tone
64
Q

What happens to the venous return curve when mean systemic filling pressure is increased?

A

The curve shifts to the right without changing slope

65
Q

What is the expected venous return at a filling pressure of 14 mmHg and right atrial pressure of 0 mmHg?

A

10 L/min

66
Q

What effect does increased sympathetic nervous system activity have on systemic filling pressure?

A

Increases systemic filling pressure

67
Q

True or False: Increased right atrial pressure typically leads to increased central venous pressure (CVP).

A

True

68
Q

What happens to venous return if systemic filling pressure is reduced to 3.5 mmHg?

A

Expected venous return decreases to 2.5 L/min

69
Q

What role do thoracic pressures play in venous return?

A

Elevated intra-thoracic pressures can cause veins to collapse

70
Q

Fill in the blank: The average pressure of the cardiovascular system is the _______.

A

Mean systemic filling pressure (PSF)

71
Q

What is the significance of the delta P in the context of the cardiovascular system?

A

It determines the pressure difference for filling the heart

72
Q

What is the effect of increased venous tone on systemic filling pressure?

A

Increases systemic filling pressure

73
Q

How does the compliance of veins affect mean systemic filling pressure?

A

Veins can hold more volume at lower pressure

74
Q

What happens if the pressure in the thorax is not compensated for the internal pressure of the veins?

A

The chest veins may collapse before delivering blood to the heart.

75
Q

How does the thorax influence the heart?

A

Both sides of the heart are influenced by thoracic conditions, affecting blood flow from the right to the left heart.

76
Q

What can mechanical ventilation do to venous return?

A

Mechanical ventilation can make it harder or easier for blood to return to the heart.

77
Q

What is the expected cardiac output with a right atrial pressure of zero in a healthy heart?

A

Approximately five liters per minute.

78
Q

What happens to cardiac output with increased right atrial pressure in a healthy heart?

A

Cardiac output increases significantly until it tops out at about 13 liters per minute.

79
Q

What is the Frank-Starling mechanism?

A

It refers to the alignment of cross bridges in ventricular muscle fibers that improves contractility with increased filling pressures.

80
Q

What is direct atrial stretch?

A

A phenomenon where increased atrial stretch leads to a slight increase in heart rate and contractility.

81
Q

What is the Bainbridge reflex?

A

A reflex that increases heart rate to accommodate higher filling pressures, requiring nervous system involvement.

82
Q

What are the two key outputs of the Bainbridge reflex?

A
  • Increase in sympathetic output
  • Decrease in parasympathetic output
83
Q

What happens to cardiac output in a heart with maximum sympathetic stimulation?

A

Cardiac output can plateau around 23 to 25 liters per minute in healthy individuals and up to 40 L/min in elite athletes.

84
Q

What effect does a strong heart contraction have on right atrial pressure?

A

It can lower the right atrial pressure compared to normal levels.

85
Q

How does a heart in failure affect right atrial pressure and filling pressures?

A

In heart failure, right atrial pressure increases, requiring higher filling pressures to maintain cardiac output.

86
Q

What is the relationship between cardiac output and venous return?

A

Cardiac output must equal venous return.

87
Q

What happens to the cardiac output if filling pressure is increased significantly?

A

The venous return curve shifts right, potentially increasing cardiac output to 13 liters per minute.

88
Q

What is the impact of stimulating the heart strongly without changing circulatory conditions?

A

Cardiac output increases only slightly, perhaps to about six liters per minute.

89
Q

Fill in the blank: The heart’s pumping effectiveness can be improved by _______.

A

[maximal sympathetic stimulation]

90
Q

True or False: The Bainbridge reflex requires special neural input to function.

A

False

91
Q

What two changes can significantly increase cardiac output?

A
  • Strongly stimulating the heart
  • Increasing the filling pressure
92
Q

What happens if blood return to the heart is not improved?

A

Cardiac output change is limited

93
Q

True or False: Stimulating the heart alone will lead to a significant increase in cardiac output.

A

False

94
Q

What is required to achieve maximal cardiac output?

A

Coordination of both heart stimulation and improved blood return

95
Q

Fill in the blank: If blood is returned to the heart better, cardiac output _______.

A

picks up a lot

96
Q

What role does the contractile state of the heart play in increasing cardiac output?

A

Not significantly affected if blood return is improved

97
Q

What advantage is gained by allowing more blood to return to the heart?

A

The heart acts as a stronger pump

A&P2 Spring 25’ (6 decks)

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