[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
- Health of the heart
- Health of the system
2
Q
What does delta p represent in the context of venous return?
A
The difference between systemic pressure and right atrial pressure
3
Q
What indicates low resistance to venous return?
A
An easy pathway for blood flow back to the heart
4
Q
How is high resistance to venous return indicated on a curve?
A
By a lower than normal slope
5
Q
True or False: Changes in resistance to venous return affect systemic filling pressure.
A
False
6
Q
What happens to venous return if right atrial pressure increases while systemic filling pressure remains unchanged?
A
Venous return decreases
7
Q
What effect does a hyper effective heart have on right atrial pressure?
A
It decreases right atrial pressure
8
Q
What is the relationship between right atrial pressure and venous return?
A
Higher right atrial pressure leads to lower venous return
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
10
Q
What is the effect of a reduction in systemic filling pressure on venous return?
A
It reduces venous return
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]
12
Q
What physiological response occurs during exercise to enhance cardiac output?
A
Constriction of arteries and veins
13
Q
What is the role of venous constriction during exercise?
A
To augment the amount of blood being returned to the heart
14
Q
How does positive pressure ventilation affect venous return?
A
It decreases venous return
15
Q
What is the primary obstacle to blood flow back to the heart during positive pressure ventilation?
A
Increased pressure in the chest
16
Q
What is the main action of phenylephrine in the venous system?
A
It tightens up the veins
17
Q
What is the normal maximum cardiac output without sympathetic stimulation?
A
13 L/min
18
Q
What can the maximum cardiac output reach with sympathetic stimulation?
A
Up to 25 L/min or more in trained athletes
19
Q
What happens to cardiac output with maximum parasympathetic stimulation?
A
It reduces cardiac output
20
Q
How does a hypo-effective heart affect right atrial pressure?
A
It increases right atrial pressure
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
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
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
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]
25
What happens to right atrial pressure when the heart is pumping effectively?
It decreases
26
What is the effect of sympathetic stimulation on cardiac output without changes to the circulatory system?
It is capped at 6 L/min
27
What happens to right atrial pressure in a strong heart?
It drops slightly, but cardiac output doesn’t increase significantly
## Footnote
This indicates the efficiency of the heart as a pump.
28
What characterizes a weak heart in terms of cardiac output and right atrial pressure?
Cardiac output decreases and right atrial pressure increases
## Footnote
A weak heart may result from conditions such as myocardial infarction (MI).
29
What happens to central venous pressure (CVP) in patients with heart problems?
CVP is almost always elevated
## Footnote
This elevation is due to the heart's struggle to pump returning blood.
30
In heart failure, what happens to right atrial pressure and cardiac output?
Right atrial pressure increases and cardiac output is very low
## Footnote
The body compensates by increasing filling pressure to attempt to sustain life.
31
What compensatory mechanism does the body use for heart problems?
Increases filling pressures to aid the struggling pump
## Footnote
This helps to improve cardiac output despite heart dysfunction.
32
How do anesthetics affect systemic filling pressure?
They reduce systemic filling pressure by relaxing blood vessels
## Footnote
This can lead to complications in patients who are dependent on high filling pressures to maintain cardiac output.
33
What is the relationship between metabolic rate and cardiac output?
Higher metabolic rate typically leads to increased cardiac output
## Footnote
This is achieved through the dilation of blood vessels in active tissues.
34
What effect does hypothyroidism have on cardiac output?
It reduces metabolic rate, leading to lower cardiac output
## Footnote
Increased vascular resistance can also contribute to this decrease.
35
What happens to cardiac output with hyperthyroidism?
It increases due to a higher metabolic rate and lower vascular resistance
## Footnote
This results in tissues requiring more blood flow.
36
What is BeriBeri and its effect on cardiac output?
A vitamin B1 deficiency that increases tissue energy demands, leading to higher cardiac output
## Footnote
Cells become less efficient in energy use, necessitating more blood delivery.
37
What effect does an AV shunt have on vascular resistance?
It reduces vascular resistance
## Footnote
This occurs because it creates an additional pathway for blood flow.
38
How is oxygen consumption related to cardiac output?
Increases in oxygen consumption are matched by increases in cardiac output
## Footnote
This relationship highlights the body's ability to meet metabolic demands.
39
What is the impact of dinitrophenol on metabolic rate?
It drives up the metabolic rate of tissues
## Footnote
This results in increased cardiac output if the nervous system functions normally.
40
True or False: The intersection of the normal venous return curve and the cardiac output curve indicates the volume of venous return.
True
## Footnote
Cardiac output must equal venous return for balance in the circulatory system.
41
Fill in the blank: If the metabolic rate is low, we can get away with a _______ cardiac output.
lower
## Footnote
Tissue needs are less, allowing for a reduced output.
42
What happens to cardiac output if there is a significant loss of tissue (e.g., kidney donation)?
Cardiac output can be lower due to reduced metabolic needs
## Footnote
Fewer blood vessels lead to higher vascular resistance.
43
What happens to cardiac output when Dinitrophenol is administered to a normal individual?
Cardiac output goes way up
## Footnote
Dinitrophenol acts as a metabolic stimulant.
44
What occurs when Dinitrophenol is administered to someone with a massive deficiency in their sympathetic nervous system?
Arteries dilate, but veins do not constrict, leading to low filling pressures
## Footnote
This results in an inability to increase cardiac output.
45
What is the primary determinant of filling pressures in the cardiovascular system?
Venous tone
46
How does the lack of venous constriction affect blood pressure when metabolic rate increases?
Blood pressure crashes
47
What is the cardiac index?
Cardiac output divided by surface area of the body (L/min/m^2)
48
What is the typical cardiac index for a healthy 70 kg adult?
About 3
49
At what age does cardiac index typically max out?
Around age 10
50
What happens to cardiac index as we age?
It decreases due to loss of muscle mass and lower energy requirements
51
What is the typical cardiac index for a reasonably healthy 80-year-old patient?
About 2.4
52
What must be true for cardiac outputs between the two sides of the heart?
They must be fairly evenly matched
53
What is the right atrial pressure typically compared to left atrial pressure?
Right atrial pressure is 0, left atrial pressure is about 2
54
Which side of the heart works harder, and why?
The left side because it pumps against higher resistance
55
What is the relationship between central venous pressure (CVP) and right atrial pressure?
They typically move together; CVP increases with right atrial pressure
56
How does distance from the heart affect pressure measurements?
The further away you measure, the higher the pressure reading
57
What is mean circulatory filling pressure?
It is essentially the same as mean systemic filling pressure, around 7
58
What happens to systemic pressure with increased volume?
Pressure in the system goes up
59
What is the effect of strong sympathetic stimulation on filling pressure?
Increases the pressure in the system
60
What effect does an AV fistula have on cardiac output?
Increases cardiac output due to low resistance to venous return
61
What is the biggest obstacle to venous return?
High pressures in the thorax
62
What happens to cardiac function during progressive hemorrhagic shock?
Volume loss leads to decreased cardiac output and heart weakening
63
How does early intervention affect outcomes in hemorrhagic shock?
Better chance to prevent heart tissue from dying due to inadequate blood supply
64
What influences the cardiac output curves?
They can shift from right to left.
65
What is the normal intrapleural pressure?
-4 mmHg
66
What happens to thoracic pressure during inspiration?
It becomes more negative.
67
What is the function of the diaphragm during inspiration?
It contracts and shifts down.
68
What effect does inspiration have on cardiac output?
Cardiac output increases.
69
What happens during forceful expiration?
Increased pressures in the chest occur.
70
What is the expected cardiac output when pleural pressure is sustained at a higher-than-normal level?
Cardiac output is expected to be low.
71
What compensatory mechanism occurs when pleural pressure is chronically high?
The body tries to increase filling pressure.
72
What could cause the cardiac output curve to shift to the right?
Fluid surrounding the heart.
73
What is the effect of a hypo effective heart on the cardiac output curve?
The plateau phase is lower than normal.
74
What does a hyper effective heart do to the cardiac output curve?
It raises the plateau phase.
75
What is systemic vascular resistance primarily governed by?
The arterioles.
76
What effect do arterial-specific vasodilators have on systemic vascular resistance?
They reduce SVR.
77
What is the impact of dilating veins on filling pressure?
It reduces filling pressure.
78
Fill in the blank: During inspiration, the cardiac output curve shifts _______.
to the left.
79
True or False: The cardiac output will increase if the pleural pressure is higher than normal.
False.
80
What happens to right atrial pressure when cardiac output is enhanced?
It should be reduced.
81
What is a common example of an arterial-specific vasodilator?
ACE inhibitor.
82
What does a sustained positive pressure around the heart likely cause?
A drop in cardiac output.
83
What is the role of the circulatory system in relation to cardiac output?
The heart pumps out what is being returned to it.
84
What could be a result of having extra fluid surrounding the heart?
Filling problems and lower cardiac output.
85
What does the pressure in the system do when arterioles are dilated?
It doesn't change much overall.
86
What happens if the heart cannot fill adequately due to excess pressure?
Cardiac output will be really bad.
87
What is the effect of dilating veins on filling pressure?
It probably reduces filling pressure.
## Footnote
Dilating veins affects the part of the circuit responsible for filling pressure, specifically central venous pressure (CVP).
88
How does dilating large arteries affect filling pressure?
It reduces filling pressure significantly.
## Footnote
This reduction can lead to a decreased delta P.
89
What happens to cardiac output if filling pressure is lower without any heart changes?
Cardiac output will be much lower.
## Footnote
Normal filling pressure is around 7 mmHg.
90
Does a change in filling pressure affect the slope of the venous return curve?
It doesn't necessarily have much effect on the slope.
## Footnote
Filling pressure being low does not significantly ease or complicate blood return to the heart.
91
What is the primary effect of nitroglycerin during heart attacks?
It reduces preload, decreasing workload on the heart.
## Footnote
This helps preserve ischemic or infarcting tissues.
92
What is a mixed vasodilator's effect on filling pressure?
It likely results in low filling pressure due to venodilation.
## Footnote
Mixed vasodilators affect both arterioles and veins.
93
In the context of venous return, which change is more important: filling pressure or resistance to venous return?
Filling pressure is more important.
## Footnote
Changes in filling pressure typically outweigh changes in resistance.
94
How can filling pressure be increased?
By constricting veins or adding volume to the system.
## Footnote
Both actions increase filling pressure without changing blood return paths.
95
What does a reduction in venous compliance indicate?
It means the veins are tighter and less stretchy.
## Footnote
Reduced compliance typically results in higher filling pressure.
96
What happens to cardiac output when changes in filling pressure occur without any heart function changes?
There are large changes in cardiac output.
## Footnote
These changes can be either higher or lower based on the direction of the filling pressure change.
97
What is the expected outcome of venous constriction?
It increases pressure and can improve venous return.
## Footnote
This can help in situations where the heart's pumping effectiveness is reduced.
98
What compensatory mechanisms occur when transitioning from a normal heart to a damaged heart?
Veins tighten and systemic vascular resistance (SVR) likely increases.
## Footnote
These changes help maintain cardiac output during heart damage.
99
What long-term change might the body make to assist a damaged heart?
It can expand blood volume.
## Footnote
This helps maintain venous return without sustained vasoconstriction.
100
True or False: The body prefers to keep sympathetic stimulation at high levels to maintain blood pressure.
False.
## Footnote
The body typically reduces vessel constriction by increasing blood volume instead.
101
Fill in the blank: A reduction in compliance of the venous system indicates that the walls are ______.
tighter.
## Footnote
Tighter walls correspond to less compliance and higher filling pressure.
