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Physiology Block 1- Cardiovascular Physiology > Ventricular Function > Flashcards

Ventricular Function Flashcards

(80 cards)

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1
Q

What is the formula for cardiac output?

A

CO= HR x SV

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2
Q

How can the heart change cardiac output?

A

By changing the Heart Rate or Stroke Volume

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3
Q

What mediates intrinsic control of cardiac output?

A

The SA node

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4
Q

What mediates extrinsic control of cardiac output?

A

The ANS

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5
Q

Where in the heart do fast response action potentials occur?

A

In the ventricle

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6
Q

Where do slow response action potentials occur?

A

SA node, AV node

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7
Q

What is the effect of sympathetics on heart rate?

A

SNS increases HR

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8
Q

Where does the SNS innervate the heart?

A

SA and AV nodes as well as ventricular muscle

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9
Q

What is the effect of PNS on heart rate?

A

PNS decreases HR

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10
Q

What part of the action potential does autonomics mainly affect?

A

phase 4 depolarization

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11
Q

What causes the gradual decay toward threshold in slow response action potentials?

A

Sodium leaking in through F-type channels plus calcium moving in through the T channels

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12
Q

How is parasympathetic control of heart rate mediated?

A

Release of ACh, which binds to muscarinic receptors, leading to increased K+ conductance (efflux), which decreases the membrane potential

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13
Q

How is sympathetic innervation of the heart rate mediated?

A

Release of NE, which binds to beta-1 receptors, increasing cAMP and leading to increased activity of the I(f) current

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14
Q

How can the maximum heart rate be calculated?

A

HR= 220(+/-20) - age

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15
Q

What is the mechanism of atropine?

A

Blocks muscarinic receptors

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16
Q

What is the mechanism of propranolol?

A

Blocks beta-1 receptors

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17
Q

What part of the autonomic nervous system has the most effect on heart rate at rest?

A

Parasympathetics

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18
Q

What nerve mediates parasympathetic innervation to the heart?

A

Vagus n.

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19
Q

What serves as intrinsic control for regulation of stoke volume?

A

Length-tension relationships (cross bridges)

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20
Q

How does the ANS regulate stroke volume?

A

Influencing contractility

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21
Q

What are the two types of contraction seen in isolated cardiac muscle?

A

Isometric and isotonic contraction

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22
Q

What is isometric contraction?

A

Contraction of cardiac muscle in which the muscle does not shorten but is still developing tension or force

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23
Q

What is an isotonic contraction?

A

Contraction of cardiac muscle such that there is o change in tension or force but shortening or a change in length does occur

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24
Q

What is the effect of increasing the resting muscular length on cardiac output? Why?

A

Cardiac output is increased because increasing the length of the muscle increases theamount of cross-bridges forming

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25
What is developed/active tension? To what part of the cardiac cycle does it correspond?
Developed tension= total tension- passive tension; corresponds to systole
26
What allows cardiac muscle cell length to change during diastole in the whole heart?
EDV increases length in heart cells
27
What is the primary mechanism by which we exhibit the length-tension relationship?
How many cross-bridges can form (overlap of myosin and actin)
28
What is the physiologic afterload?
The tension developed in the ventricular wall that resists ventricular ejection or the arterial input impedance
29
What is the effect of increasing arterial pressure on afterload?
Increases afterload
30
How much tension will the cardiac muscle develop?
Enough to match the afterload
31
What is the effect of a lower afterload on the velocity of shortening?
Lower afterload means the muscle can reach tension faster and shorten faster
32
What are the effects of increasing the afterload on ventricular muscle?
Slower and less shortening of the muscle
33
Why does increasing the afterload cause less shortening of the muscle?
During contraction the muscles has to develop more tension to match the higher afterload which uses up more energy and so less energy remains for shortening
34
What is the point at which there is no shortening? What causes this?
Isometric contraction; The afterload is too high for muscle to develop tension and still shorten
35
What is the effect of increasing the preload?
Increases the resting length causing more cross bridge formation, more myosin ATPase activity, more ATP hydrolysis, more available ATP, and stronger contraction
36
What determines how much tension is developed in cardiac muscle?
Afterload
37
What determines how many cross bridges will interact in ventricular cardiac muscle?
Preload
38
What determines how much energy is available for contraction?
Preload
39
What is the effect of increasing contractility on isometric contraction and Vmax? What mediates these effects?
Po and Vmax increase; due to mainly SNS factors
40
How does the sympathetic nervous system mediate increased contractility?
NE binds to beta-1 receptors, activating adenylyl cyclase, increasing cAMP and activting PKA leading to an increase in Ca2+ and stronger contraction
41
What is the effect of increasing preload on contraction strength?
Increasing preload leads to increased strength of contraction
42
Before the muscle can shorten, what must occur?
It must develop tension to match whatever the afterload is on it
43
How can tension be calculated using the Law of LaPlace?
Tension= Pressure x radius
44
What is the analagous to the length-tension relationship on the whole-heart level?
Frank-Starling Mechanism
45
What is the physiologic preload in the heart? How does this affect length?
End-diastolic volume; higher volume in the ventricles causes the cells to stretch more
46
When does the heart develop active tension? When does it have passive tension
Systole; diastole
47
How is tension of the whole heart represented?
Left Ventricular Pressure
48
What does LAP at the end of diastole give an indication of?
Left Ventricular EDP
49
What is the most important property of the ventricle in lower pressures?
Compliane
50
End diastolic pressure is an estimate of what?
End diastolic volume
51
What is used to measure pulmonary capillary wedge pressure?
Swan-Ganz catheter
52
If a Swan-Ganz catheter is wedged into a small pulmonary artery such that it is occluding blood flow, what pressure is being measured?
Pulmonary capillary pressure (reflection of LAP)
53
What determines what ventricular pressure develops?
Aortic pressure
54
What is the difference in stroke volume and cardiac output?
The ventricle pumps its stroke volume each time it contracts, and it pumps cardiac output over a minute
55
When is left ventricular pressure developed?
Isovolumic contraction
56
What determines isolvolumic contraction?
Aortic pressure
57
What is the relationship between aortic pressure and the left ventricle
Aortic pressure is the afterload of the left ventricle
58
What is the afterload of the right ventricle?
Pulmonary artery pressure
59
What is the formula for work?
W= volume x pressure
60
How is stroke work calculated?
SW= MABP x SV
61
How is minute work calculated?
MW= MABP x CO
62
What is the typical value of the afterload of the heart?
about 93 mmHg
63
What is the approximate pressure needed for the ventricle to open the aortic valve?
about 80 mmHg
64
What is the relationship between afterload and velocity of contraction?
Inverse relationship
65
What is the relationship between cardiac muscle shortening and stroke volume?
Less shortening= less stroke volume
66
An increase in EDV would have what effect on stroke volume?
Increase
67
Is the Frank-Starling Mechanism intrinsic or extrinsic?
Intrinsic
68
What happens to the ejection fraction during the Frank-Starling mechanism?
Stays the same
69
What point of a pressure-volume loop represents end diastolic volume?
Bottom right corner
70
What does the top right corner of the pressure-volume loop represent?
Afterload or aortic pressure
71
What part of the pressure-volume loop represents stroke ejection?
Top of the box
72
What part of the pressure-volume loop represents end systolic volume?
Left border
73
What effect does increasing the preload have on the pressure-volume loop?
Loop shifts upward and to the right
74
What effect does increasing the afterload have on the pressure-volume loop?
The PV loop would shift upward with EDV remaining the same
75
What would result in an upward and left shift in the PV loop with the same EDV?
Increased contractility
76
If afterload is increased and PV loop is shifted up and to the right, how is stroke volume normalized?
Preload reserve and contractility reserve
77
What is the preload reserve?
A mechanism by which ppreload can be increased to deal with an increased afterload by increasing EDV, creating more cross-bridges
78
What is the contractility reserve?
A mechanism by which contractility is increased such that aortic pressure and EDV are maintained but stroke volume is increased
79
What is dP/dt?
The rate of pressure development; slope of the lines tangent to curves of LV pressure over time
80
What is the index of contractility?
Where dP/dt is max

Physiology Block 1- Cardiovascular Physiology (17 decks)

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