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Cardio/Pulm Final > Lecture 11 (DSA): Hemodynamics & Systemic Circulation > Flashcards

Lecture 11 (DSA): Hemodynamics & Systemic Circulation Flashcards

1
Q

The site of highest resistance to blood flow is within?

A

Arterioles

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2
Q

Arterioles are extensively innervated by?

A

Sympathetic nervous system

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3
Q

α1-Adrenergic receptors are found within arterioles cause what?

A

Constriction of vascular smooth muscle

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4
Q

How does constriction of arterioles affect resistance to blood flow?

A

Increases resistance, which decreases blood flow

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5
Q

β2-adrenergic receptors are found within arterioles and cause what?

A

Dilation/relaxation of the vascular smooth muscle

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6
Q

How does dilation of arterioles affect resistance to blood flow?

A

Deceases resistance, which increases blood flow

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7
Q

How do α1-Adrenergic receptors affect BP?

A

When stimulated will cause constriction of arterioles = increasing BP

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8
Q

What is the of nutrient, gas, water, and solute exchange within circulation?

A

Capillaries

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9
Q

Why are capillaries the ideal site for the exchange of substances?

A

They have a large internal surface area

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10
Q

What is the benefit of the capillaries having a large total cross-sectional area?

A

Blood moves very slowly through them, which maximizes the time for exchange across the capillary walls.

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11
Q

The largest percentage of blood in the cardiovascular system is found within?

A

Veins

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12
Q

Veins contain what kind of receptors?

A

α1-Adrenergic receptors

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13
Q

For a given flow the velocity will be _______ the larger the vessel is through which it is flowing

A

slower

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14
Q

What kind of relationships exists between velocity of flow and cross-sectional area?

A

Inverse relationship

V = Q/A

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15
Q

What is the equation for blood flow?

A

Q = (delta)P/R

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16
Q

Direction of blood flow is determined by what; and is always in what direction?

A

Direction of the pressure gradient; always from high to low pressure

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17
Q

Why does blood flow from the ventricle into the aorta and not in the other direction?

A

Pressure in the ventricle is higher than pressure in the aorta (high to low)

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18
Q

The magnitude of blood flow (Q) is directly proportional to the size of the?

A

Pressure difference (deltaP)

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19
Q

Major mechanism for changing blood flow in the CV system is by changing the resistance of blood vessels, particularly which ones?

A

Arterioles

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20
Q

How does changes to the radius of a blood vessel affect resistance?

A

Has a very powerful effect, in Poiseullie’s equation r^4

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21
Q

If the radius of a blood vessel decreases by one-half resistance will increase by?

A

16-fold (2^4)

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22
Q

If the radius of a blood vessel decreases by three-fourths the resistance will increase by?

A

1/(1/4)^4 = 4^4 = 256-fold

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23
Q

The total resistance of the system arranged in series is equal to?

A

The sum of individual resistances

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24
Q

Although total flow is constant at each level in the series, what happens to pressure?

A

Pressure decreases progressively as blood flows through each sequential component

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25
Q

Where does the greatest decrease in pressure occur for blood flow, why?

A

In the arterioles, because they contribute the largest portion of resistance

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26
Q

The total resistance in a parallel arrangement is _____ than any of the individual resistances

A

Less

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27
Q

Adding a parallel resistance does what to the total resistance?

A

Decreases total resistance

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28
Q

Adding a resistance in series does what to the total resistance?

A

Increases total resistance

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29
Q

What are the effects of parallel resistance of pressure?

A

No loss of pressure in the major arteries

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30
Q

If resistance of one of the individual vessels in a parallel arrangement increases, what happens to total resistance?

A

Increases

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31
Q

In laminar flow how does velocity near the wall of the blood vessel compare to that of the center?

A

Velocity of flow at vessel wall is zero and at the center of stream is maximal

32
Q

What is required to drive turbulent blood flow?

A

More energy (pressure)

33
Q

What occurs to the fluid streams during turbulent flow?

A

Kinetic energy is wasted due to the fluid streams mixing radially and axially

34
Q

What is heard while measuring BP caused by turbulent flow?

A

Korotkoff sounds

35
Q

Blood vessel stenosis and cardiac valve disease can cause what kind of flow; and is heard as?

A

Turbulent flow heard as murmurs.

36
Q

What is Reynolds number used for?

A

To predict whether blood flow will be laminar or turbulent

37
Q

What is the standard number used with Reynolds number?

A

If Reynold’s number is greater than 2000, likeliness of turbulent blood flow is increasing. If greater than 3000 always predict turbulent flow

38
Q

The major influences on Reynold’s number in the CV system are what two things?

A

1) Changes in viscosity

2) Changes in velocity of blood flow

39
Q

Decreases in viscosity do what to Reynold’s number?

A

Increase

40
Q

Narrowing of a blood vessel would do what to the velocity of blood flow; affect on Reynold’s number?

A

Increase velocity and increase Reynold’s number.

41
Q

How does anemia affect Reynold’s number?

A
  • Decreased hematocrit = decreased viscosity = increased Reynold’s number
  • Increased cardiac output = increased velocity = increased Reynold’s number
42
Q

What is Thrombi; how does it affect Reynold’s number?

A

Blood clots in the lumen of a vessel = decrease diameter = increased velocity = increased Reynold’s number.

43
Q

What causes shear?

A

If adjacent layers of blood travel at different velocities

44
Q

Where is shear highest?

A

Between the motionless layer of blood at the vessel wall and the next layers

45
Q

Where is shear lowest?

A

The center of the blood vessel where the velocity of blood is highest, and adjacent layers of blood are essentially moving at the same velocity

46
Q

What is a consequence of shear?

A

Breaks up aggregates of RBC’s and decreases blood viscosity

*At wall shear is highest, viscosity and RBC aggregates are lowest

47
Q

What is compliance or capacitance of a blood vessel?

A

The volume of blood the vessel can hold at a given pressure

  • C = V/P
48
Q

Which has higher compliance, veins or arteries?

A

Veins have the highest compliance

49
Q

Why do veins have higher compliance?

A

Hold larger amounts of blood at lower pressures

50
Q

What occurs if there is a decrease in compliance of the veins?

A

Volume of blood they can hold will decrease and there will be a shift of blood from the veins —> arteries

51
Q

How does compliance change as an artery ages?

A

There will be a decrease in compliance. At a given arterial pressure, the arteries can hold less blood.

52
Q

What occurs as arteries age?

A
  • Walls become stiffer
  • Less distensible
  • Less compliant
53
Q

Why do elderly individuals arterial pressures increase?

A

To compensate for the decreased compliance

54
Q

What is the driving force for blood flow?

A

The pressure differences that exist between the heart and the blood vessels

55
Q

Where is mean pressure highest?

A

The aorta and large arteries

56
Q

What 2 factors cause the high mean arterial pressure in the aorta?

A

1) Large volume of blood pumped from the left ventricle

2) Low compliance of arterial wall

57
Q

Where do you see the most significant decrease in arterial pressure?

A

The arterioles

*High resistance to flow

58
Q

Since total blood flow is constant at all levels of the CVS, what must occur as the resistance increases?

A

The pressure must decrease

Q = deltaP/R

59
Q

What are the 2 reasons pressure decreases in the capillaries?

A

1) Frictional resistance to flow

2) Filtration of fluid out of the capillaries

60
Q

Diastolic pressure

A

Lowest arterial pressure measured during a cardiac cycle and is pressure during ventricular relaxation

61
Q

Systolic pressure

A

Highest arterial pressure measure during cardiac cycle and is pressure in arteries after blood has been ejected from left ventricle

62
Q

The difference between systolic and diastolic pressure is known as?

A

Pulse pressure

63
Q

The magnitude of the pulse pressure reflects?

A

Volume of blood ejected from the left ventricle on a single beat, stroke volume.

64
Q

Mean arterial pressure; calculation?

A

Average pressure in a complete cardiac cycle

Diastolic pressure + 1/3Pulse pressure

or

((2 x diastolic) + systolic))/3

65
Q

Greatest fraction of cardiac cycle is spent in?

A

Diastole

66
Q

Systolic and pulse pressure are higher in _______ than the aorta

A

Large arteries

67
Q

Why is systolic and pulse pressure higher in large arteries than in the aorta?

A

Following ejection of blood from ventricle, the pressure wave travels at a higher velocity than the blood itself

68
Q

Is diastolic pressure higher or lower in the large arteries than in the aorta?

A

Lower in the large arteries

69
Q

What 2 factors cause the dampening and loss of pulse pressure downstream?

A

1) Resistance of the blood vessels, particularly the arterioles
2) Compliance of the blood vessels, particularly the veins

70
Q

What is arteriosclerosis?

A

Plaque deposits in arterial walls decrease the diameter of the arteries, decreasing compliance

71
Q

How is systolic pressure, pulse pressure, and mean pressure affected in arteriosclerosis?

A

All increased

72
Q

How does aortic stenosis affect stroke volume, systolic pressure, pulse pressure, and mean pressure?

A
  • Size of opening which blood can be ejected is narrowed so stroke volume decreases
  • Systolic, pulse, and mean pressure will all decrease
73
Q

By the time blood reaches the venules and veins, pressure is less than?

A

10 mmHg

74
Q

How does pulmonary pressure compares to systemic vasculature?

A

Much lower in pulmonary vasculature

75
Q

How is pulmonary pressure analogous to systemic?

A

Pulmonary artery (highest pressure). The pressure decreases as blood moves on to arterioles, capillaries, venules, veins, and back to the left atrium.

76
Q

Why is there lower pressure on the pulmonary side?

A

The pulmonary vascular resistance is much lower than systemic resistance.

77
Q

Why is it crucial for pulmonary vascular resistance to be low?

A

Allows for total flow through systemic and pulmonary vasculature to be equal, even with such low pressure on the pulmonary side.

Cardio/Pulm Final (18 decks)

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