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A&P II (Spring 2025) > [Exam 1] Lecture 3: Cardiac Output & Venous Return Curves Continued [1-23-25] > Flashcards

[Exam 1] Lecture 3: Cardiac Output & Venous Return Curves Continued [1-23-25] Flashcards

1
Q

What are the two components that determine cardiac output?

A
  1. Health of the heart
  2. Health of the system
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2
Q

What does delta p represent in the context of venous return?

A

The difference between systemic pressure and right atrial pressure

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3
Q

What indicates low resistance to venous return?

A

An easy pathway for blood flow back to the heart

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4
Q

How is high resistance to venous return indicated on a curve?

A

By a lower than normal slope

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5
Q

True or False: Changes in resistance to venous return affect systemic filling pressure.

A

False

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6
Q

What happens to venous return if right atrial pressure increases while systemic filling pressure remains unchanged?

A

Venous return decreases

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7
Q

What effect does a hyper effective heart have on right atrial pressure?

A

It decreases right atrial pressure

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8
Q

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

A

Higher right atrial pressure leads to lower venous return

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9
Q

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

A

The curve shifts to the right, indicating higher venous return

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10
Q

What is the effect of a reduction in systemic filling pressure on venous return?

A

It reduces venous return

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11
Q

Fill in the blank: The systemic filling pressure is defined by the point at which the _______ curve runs into the x-axis.

A

[venous return]

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12
Q

What physiological response occurs during exercise to enhance cardiac output?

A

Constriction of arteries and veins

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13
Q

What is the role of venous constriction during exercise?

A

To augment the amount of blood being returned to the heart

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14
Q

How does positive pressure ventilation affect venous return?

A

It decreases venous return

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15
Q

What is the primary obstacle to blood flow back to the heart during positive pressure ventilation?

A

Increased pressure in the chest

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16
Q

What is the main action of phenylephrine in the venous system?

A

It tightens up the veins

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17
Q

What is the normal maximum cardiac output without sympathetic stimulation?

A

13 L/min

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18
Q

What can the maximum cardiac output reach with sympathetic stimulation?

A

Up to 25 L/min or more in trained athletes

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19
Q

What happens to cardiac output with maximum parasympathetic stimulation?

A

It reduces cardiac output

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20
Q

How does a hypo-effective heart affect right atrial pressure?

A

It increases right atrial pressure

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21
Q

What happens to the cardiac output curve if the heart is ineffective due to an MI?

A

The cardiac output curve shifts down significantly

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22
Q

What does the intersection point of the venous return curve and cardiac output curve indicate?

A

The actual conditions of the circulatory system

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23
Q

What is the effect of massive sympathetic stimulation on cardiac output with normal circulatory parameters?

A

It increases cardiac output slightly to around 6 L/min

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24
Q

Fill in the blank: The body enhances cardiac output by increasing systemic filling pressure through both _______ and _______.

A

[artery constriction] and [venous constriction]

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25
Q

What happens to right atrial pressure when the heart is pumping effectively?

A

It decreases

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26
Q

What is the effect of sympathetic stimulation on cardiac output without changes to the circulatory system?

A

It is capped at 6 L/min

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27
Q

What happens to right atrial pressure in a strong heart?

A

It drops slightly, but cardiac output doesn’t increase significantly

This indicates the efficiency of the heart as a pump.

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28
Q

What characterizes a weak heart in terms of cardiac output and right atrial pressure?

A

Cardiac output decreases and right atrial pressure increases

A weak heart may result from conditions such as myocardial infarction (MI).

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29
Q

What happens to central venous pressure (CVP) in patients with heart problems?

A

CVP is almost always elevated

This elevation is due to the heart’s struggle to pump returning blood.

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30
Q

In heart failure, what happens to right atrial pressure and cardiac output?

A

Right atrial pressure increases and cardiac output is very low

The body compensates by increasing filling pressure to attempt to sustain life.

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31
Q

What compensatory mechanism does the body use for heart problems?

A

Increases filling pressures to aid the struggling pump

This helps to improve cardiac output despite heart dysfunction.

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32
Q

How do anesthetics affect systemic filling pressure?

A

They reduce systemic filling pressure by relaxing blood vessels

This can lead to complications in patients who are dependent on high filling pressures to maintain cardiac output.

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33
Q

What is the relationship between metabolic rate and cardiac output?

A

Higher metabolic rate typically leads to increased cardiac output

This is achieved through the dilation of blood vessels in active tissues.

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34
Q

What effect does hypothyroidism have on cardiac output?

A

It reduces metabolic rate, leading to lower cardiac output

Increased vascular resistance can also contribute to this decrease.

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35
Q

What happens to cardiac output with hyperthyroidism?

A

It increases due to a higher metabolic rate and lower vascular resistance

This results in tissues requiring more blood flow.

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36
Q

What is BeriBeri and its effect on cardiac output?

A

A vitamin B1 deficiency that increases tissue energy demands, leading to higher cardiac output

Cells become less efficient in energy use, necessitating more blood delivery.

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37
Q

What effect does an AV shunt have on vascular resistance?

A

It reduces vascular resistance

This occurs because it creates an additional pathway for blood flow.

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38
Q

How is oxygen consumption related to cardiac output?

A

Increases in oxygen consumption are matched by increases in cardiac output

This relationship highlights the body’s ability to meet metabolic demands.

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39
Q

What is the impact of dinitrophenol on metabolic rate?

A

It drives up the metabolic rate of tissues

This results in increased cardiac output if the nervous system functions normally.

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40
Q

True or False: The intersection of the normal venous return curve and the cardiac output curve indicates the volume of venous return.

A

True

Cardiac output must equal venous return for balance in the circulatory system.

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41
Q

Fill in the blank: If the metabolic rate is low, we can get away with a _______ cardiac output.

A

lower

Tissue needs are less, allowing for a reduced output.

42
Q

What happens to cardiac output if there is a significant loss of tissue (e.g., kidney donation)?

A

Cardiac output can be lower due to reduced metabolic needs

Fewer blood vessels lead to higher vascular resistance.

43
Q

What happens to cardiac output when Dinitrophenol is administered to a normal individual?

A

Cardiac output goes way up

Dinitrophenol acts as a metabolic stimulant.

44
Q

What occurs when Dinitrophenol is administered to someone with a massive deficiency in their sympathetic nervous system?

A

Arteries dilate, but veins do not constrict, leading to low filling pressures

This results in an inability to increase cardiac output.

45
Q

What is the primary determinant of filling pressures in the cardiovascular system?

A

Venous tone

46
Q

How does the lack of venous constriction affect blood pressure when metabolic rate increases?

A

Blood pressure crashes

47
Q

What is the cardiac index?

A

Cardiac output divided by surface area of the body (L/min/m^2)

48
Q

What is the typical cardiac index for a healthy 70 kg adult?

A

About 3

49
Q

At what age does cardiac index typically max out?

A

Around age 10

50
Q

What happens to cardiac index as we age?

A

It decreases due to loss of muscle mass and lower energy requirements

51
Q

What is the typical cardiac index for a reasonably healthy 80-year-old patient?

A

About 2.4

52
Q

What must be true for cardiac outputs between the two sides of the heart?

A

They must be fairly evenly matched

53
Q

What is the right atrial pressure typically compared to left atrial pressure?

A

Right atrial pressure is 0, left atrial pressure is about 2

54
Q

Which side of the heart works harder, and why?

A

The left side because it pumps against higher resistance

55
Q

What is the relationship between central venous pressure (CVP) and right atrial pressure?

A

They typically move together; CVP increases with right atrial pressure

56
Q

How does distance from the heart affect pressure measurements?

A

The further away you measure, the higher the pressure reading

57
Q

What is mean circulatory filling pressure?

A

It is essentially the same as mean systemic filling pressure, around 7

58
Q

What happens to systemic pressure with increased volume?

A

Pressure in the system goes up

59
Q

What is the effect of strong sympathetic stimulation on filling pressure?

A

Increases the pressure in the system

60
Q

What effect does an AV fistula have on cardiac output?

A

Increases cardiac output due to low resistance to venous return

61
Q

What is the biggest obstacle to venous return?

A

High pressures in the thorax

62
Q

What happens to cardiac function during progressive hemorrhagic shock?

A

Volume loss leads to decreased cardiac output and heart weakening

63
Q

How does early intervention affect outcomes in hemorrhagic shock?

A

Better chance to prevent heart tissue from dying due to inadequate blood supply

64
Q

What influences the cardiac output curves?

A

They can shift from right to left.

65
Q

What is the normal intrapleural pressure?

A

-4 mmHg

66
Q

What happens to thoracic pressure during inspiration?

A

It becomes more negative.

67
Q

What is the function of the diaphragm during inspiration?

A

It contracts and shifts down.

68
Q

What effect does inspiration have on cardiac output?

A

Cardiac output increases.

69
Q

What happens during forceful expiration?

A

Increased pressures in the chest occur.

70
Q

What is the expected cardiac output when pleural pressure is sustained at a higher-than-normal level?

A

Cardiac output is expected to be low.

71
Q

What compensatory mechanism occurs when pleural pressure is chronically high?

A

The body tries to increase filling pressure.

72
Q

What could cause the cardiac output curve to shift to the right?

A

Fluid surrounding the heart.

73
Q

What is the effect of a hypo effective heart on the cardiac output curve?

A

The plateau phase is lower than normal.

74
Q

What does a hyper effective heart do to the cardiac output curve?

A

It raises the plateau phase.

75
Q

What is systemic vascular resistance primarily governed by?

A

The arterioles.

76
Q

What effect do arterial-specific vasodilators have on systemic vascular resistance?

A

They reduce SVR.

77
Q

What is the impact of dilating veins on filling pressure?

A

It reduces filling pressure.

78
Q

Fill in the blank: During inspiration, the cardiac output curve shifts _______.

A

to the left.

79
Q

True or False: The cardiac output will increase if the pleural pressure is higher than normal.

A

False.

80
Q

What happens to right atrial pressure when cardiac output is enhanced?

A

It should be reduced.

81
Q

What is a common example of an arterial-specific vasodilator?

A

ACE inhibitor.

82
Q

What does a sustained positive pressure around the heart likely cause?

A

A drop in cardiac output.

83
Q

What is the role of the circulatory system in relation to cardiac output?

A

The heart pumps out what is being returned to it.

84
Q

What could be a result of having extra fluid surrounding the heart?

A

Filling problems and lower cardiac output.

85
Q

What does the pressure in the system do when arterioles are dilated?

A

It doesn’t change much overall.

86
Q

What happens if the heart cannot fill adequately due to excess pressure?

A

Cardiac output will be really bad.

87
Q

What is the effect of dilating veins on filling pressure?

A

It probably reduces filling pressure.

Dilating veins affects the part of the circuit responsible for filling pressure, specifically central venous pressure (CVP).

88
Q

How does dilating large arteries affect filling pressure?

A

It reduces filling pressure significantly.

This reduction can lead to a decreased delta P.

89
Q

What happens to cardiac output if filling pressure is lower without any heart changes?

A

Cardiac output will be much lower.

Normal filling pressure is around 7 mmHg.

90
Q

Does a change in filling pressure affect the slope of the venous return curve?

A

It doesn’t necessarily have much effect on the slope.

Filling pressure being low does not significantly ease or complicate blood return to the heart.

91
Q

What is the primary effect of nitroglycerin during heart attacks?

A

It reduces preload, decreasing workload on the heart.

This helps preserve ischemic or infarcting tissues.

92
Q

What is a mixed vasodilator’s effect on filling pressure?

A

It likely results in low filling pressure due to venodilation.

Mixed vasodilators affect both arterioles and veins.

93
Q

In the context of venous return, which change is more important: filling pressure or resistance to venous return?

A

Filling pressure is more important.

Changes in filling pressure typically outweigh changes in resistance.

94
Q

How can filling pressure be increased?

A

By constricting veins or adding volume to the system.

Both actions increase filling pressure without changing blood return paths.

95
Q

What does a reduction in venous compliance indicate?

A

It means the veins are tighter and less stretchy.

Reduced compliance typically results in higher filling pressure.

96
Q

What happens to cardiac output when changes in filling pressure occur without any heart function changes?

A

There are large changes in cardiac output.

These changes can be either higher or lower based on the direction of the filling pressure change.

97
Q

What is the expected outcome of venous constriction?

A

It increases pressure and can improve venous return.

This can help in situations where the heart’s pumping effectiveness is reduced.

98
Q

What compensatory mechanisms occur when transitioning from a normal heart to a damaged heart?

A

Veins tighten and systemic vascular resistance (SVR) likely increases.

These changes help maintain cardiac output during heart damage.

99
Q

What long-term change might the body make to assist a damaged heart?

A

It can expand blood volume.

This helps maintain venous return without sustained vasoconstriction.

100
Q

True or False: The body prefers to keep sympathetic stimulation at high levels to maintain blood pressure.

A

False.

The body typically reduces vessel constriction by increasing blood volume instead.

101
Q

Fill in the blank: A reduction in compliance of the venous system indicates that the walls are ______.

A

tighter.

Tighter walls correspond to less compliance and higher filling pressure.

A&P II (Spring 2025) (6 decks)

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