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Whitney - Physiology Test 2 > Lecture 9 Overview of Circulation > Flashcards

Lecture 9 Overview of Circulation Flashcards

1
Q

Blood flow resistance is indirectly proportional to which of the following?

a. viscosity
b. vessel diameter
c. density
d. both A and C

A

b. vessel diameter

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2
Q

Reynolds number is a measure of which of the following parameters?

a. Tendency for turbulence
b. Blood pressure
c. Conductance
d. Resistance

A

a. Tendency for turbulence

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3
Q

84% of the blood volume is in the systemic circulation. Of this, 64% is in which of the following vessels?

a. Capillaries
b. Systemic arterioles
c. Veins
d. Arterioles

A

c. veins

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4
Q

Which of the following represents the viscosity of blood with a hematocrit of 38-42?

a. 1.5
b. 3.0
c. 38
d. 42

A

b. 3.0

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5
Q

Arterial pressure from _____ mm Hg (systolic) to _____ mm Hg (diastolic)

A

120, 80

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6
Q

When does Arterial pressure drop to 0 mm Hg?

A

By the time is reaches the termination of the vena cava

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7
Q

Systemic capillary pressure varies from _____ mm Hg to _____ mm Hg

A

35, 10

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8
Q

In pulmonary circulation, what is the systolic pulmonary artery pressure?

A

25 mm Hg

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9
Q

In pulmonary circulation, what is the pulmonary diastolic pressure?

A

8 mm Hg

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10
Q

In circulation, what is the function of the arteries?

A

Transport under high pressure

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11
Q

In circulation, what is the function of the arterioles?

A

Control conduits

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12
Q

In circulation, what is the function of the capillaries?

A

exchange between blood and extracellular fluid

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13
Q

What percent of blood volume is in the systemic circulation?

A

84%

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14
Q

What percent of systemic blood volume is in the veins?

A

64%

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15
Q

What percent of systemic blood volume is in the arteries?

A

13%

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16
Q

What percent of systemic blood volume is in the systemic arterioles and capillaries?

A

7%

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17
Q

What percent of blood volume is in the heart and lungs?

A

16%

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18
Q

Formula for Velocity of Blood Flow

A

V = F/A
V (velocity of blood flow)
F (volume of blood flow)
A (vascular cross-sectional area)

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19
Q

How fast does blood travel in the aorta at rest?

A

33 cm/sec

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20
Q

How fast does blood flow in the capillaries at rest?

A

0.3 mm/sec

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21
Q

What precisely controls the rate of blood flow to each tissue?

A

It is almost always precisely controlled in relation to the tissue need

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22
Q

The cardiac output is controlled mainly by what?

A

The sum of all the local tissue flows

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23
Q

True or False

Arterial pressure regulation is generally DEPENDENT of either local blood flow control or cardiac output control

A

FALSE

Arterial pressure regulation is generally INDEPENDENT of either local blood flow control or cardiac output control

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24
Q

In each tissue, ________ monitor tissue needs

A

microvessels

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25
Q

When a tissue is in need, the heart responds to the demand. What type of signals may be needed to help the heart pump the required amount of blood?

A

Nerve signals

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26
Q

If arterial pressure falls below 100 mmHg, nervous reflexes: (4)

A

Increase force of heart pumping
Constrict large venous reservoirs
Generally constrict most of the arterioles throughout the body (increases arterial pressure)
Kidneys may later play role in pressure control

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27
Q

What factors determine blood flow?

A

Pressure difference between the two ends of a vessel (pressure gradient)
Impediment of blood flow through the vessel (resistance)

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28
Q

How do we calculate the flow through a vessel?

A

F = deltaP/R

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29
Q

Flow is _______ (directly or indirectly) proportional to pressure

A

Directly

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30
Q

Flow is _______ (directly or indirectly) proportional to resistance

A

Indirectly

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31
Q

Laminar blood flow = ?

A

Streamline flow

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32
Q

What are the characteristics of laminar blood flow?

A

Blood flows at a steady rate
Blood vessel is long and smooth
Blood flows in streamlines (layers)

33
Q

What are the characteristics of streamline flow?

A

Each layer maintains same distance from vessel wall
Central-most portion of the blood stays in the center
Each layer slips easily past surrounding layers
Velocity of fluid in center is greater than that of fluid flowing toward the outer edges

34
Q

What are the characteristics of turbulent flow?

A

Nonlayered flow
Creates murmurs
Produces more resistance than laminar flow

35
Q

When does turbulent flow occur?

A

When flow is too great
When blood passes an obstruction within the vessel
When blood has to make a sharp turn
When blood passes over a rough surface

36
Q

Tendency for turbulent flow increases in direct proportion to:

A

Velocity of blood flow
Diameter of the vessel
Density of the blood

37
Q

Tendency for turbulent flow increases inversely to:

A

Viscosity of the blood

38
Q

The density of blood depends on what?

A

Proportion of its components, particularly RBCs and proteins

39
Q

Define Blood Viscosity

A

The property of blood to adhere to vessels walls and to each other and is based on the number, shape, and size of RBCs

40
Q

What is the equation for Reynolds Number, what does it measure and what does each variable represent?

A 
Re = (v · d · ρ)/η
Measure of the tendency for turbulence to occur
v = mean velocity of blood flow
d = vessel diameter
ρ = density 
η = viscosity
41
Q

What happens when Re rises above 200-400?

A

Turbulent flow will occur in some regions of a vessel

42
Q

What happens when Re rises above 2000?

A

Turbulence will occur even in a straight vessel

43
Q

What is the meaning of “blood pressure”?

A

The force exerted by the blood against any unit area of the vessel wall

44
Q

How can pressure be measured?

A

With a mercury manometer or with electronic transducers

45
Q

Define Resistance

A

The impediment to blood flow in a vessel

46
Q

How must Resistance be calculated?

A

It must be indirectly calculated from measurements of blood flow and pressure
R = Pressure/(volume/time)

47
Q

List the three major variables that determine resistance

A

Vessel Radius (most important variable)
Blood Viscosity
Vessel Length

48
Q

If blood flow decreases, what happens to resistance?

A

Resistance increases

49
Q

If upstream pressure increases, what happens to resistance?

A

Resistance increases

50
Q

If downstream pressure increases, what happens to resistance?

A

Resistance decreases

51
Q

Know relationship of variables in this equation:

R =8ηl/πr^4

A 
R = resistance
η = viscosity of blood
l = length of vessel 
r^4 = radius of BV to the 4th power
52
Q

Why is there a low pressure drop across major arteries?

A

Because they have a low resistance

53
Q

Where is the largest pressure drop and why?

A

Largest pressure drop is across arterioles b/c they have the highest resistance

54
Q

Systolic pressure is the _______ (highest/lowest) arterial pressure during a cardiac cycle.

A

Highest

55
Q

Diastolic pressure is the ________ (highest/lowest) arterial pressure.

A

Lowest

56
Q

Define Pulse Pressure

A

Difference between systolic and diastolic pressure

57
Q

What is the rate of blood flow through the entire circulatory system?

A

Cardiac output

100 ml/sec

58
Q

What is the pressure difference from systemic arteries to systemic veins?

A

100 mmHG

59
Q

Using 100 mmHg for the pressure and 100 ml/sec for the rate of flow, what is the resistance of the entire systemic circulation?

A

100/100 = 1 PRU

60
Q

What happens to the PRU in conditions where the vessels are strongly constricted?

A

Total peripheral resistance may rise to 4 PRU

61
Q

What happens to the PRU in conditions where the vessels are greatly dilated?

A

The resistance can fall to as little as 0.2 PRU

62
Q

What is the average mean pulmonary arterial pressure?

A

16 mmHg

63
Q

What is the average mean left arterial pressure?

A

2 mmHg

64
Q

Using 16 mmHg and 2 mmHg for pulmonary arterial pressure and left arterial pressure respectively, what is the total pulmonary vascular resistance when cardiac output is normal at 100 ml/sec?

A

14/100 = 0.14 PRU

65
Q

Define Conductance

A

Measure of blood flow through a vessel for a given pressure difference

66
Q

Conductance is the exact reciprocal of _____

A

Resistance

Conductance = 1/Resistance

67
Q

Conductance is ______ (directly/indirectly) proportional to diameter^4

A

directly

68
Q

Poiseuille’s Law

A

F = πΔPr4/8ηl

69
Q

Arterioles, capillaries, venules, and veins are arranged in ________ (parallel/series)

A

Series

70
Q

Blood vessels branch extensively to form parallel circuits. For BVs arranged in parallel the total resistance to blood flow is expresses as:

A

1/Rtotal = 1/R1 + 1/R2 + 1/R3….

Therefore, total resistans is far less than the resistance of any single BV

71
Q

What is the total conductance for vessels arranged in parallel?

A

The total conductance for vessels arranged in parallel is the sum of the conductance of each parallel pathway

72
Q

List the circulation arranged in parallel

A

Brain, Kidney, Muscle, Gastrointestinal, Skin, Coronary Circulation
(Each of the above tissues contributes to the overall conductance of the systemic circulation)

73
Q

Amputation of a limb or removal of a kidney removes a parallel circuit resulting in:

A

Reduced total vascular conductance
Reduced total blood flow
Increased total peripheral vascular resistance

74
Q

Define Viscosity

A

Measure of the fluid’s internal resistance

75
Q

What is the relationship between viscosity and resistance?

A

Greater the viscosity, greater the resistance

76
Q

What is the prime determinant of blood viscosity?

A

Hematocrit

77
Q

What happens to viscosity when a person has anemia?

A

Anemia decreases viscosity

78
Q

What happens to viscosity when a person has polycythemia?

A

Polycythemia increases viscosity

79
Q

Define Blood Flow Autoregulation

A

The ability of each tissue to adjust its vascular resistance and to maintain normal blood flow through changes in arterial pressure between approximately 70 and 175 mmHg

Whitney - Physiology Test 2 (8 decks)

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