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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
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?
Nerve signals
26
If arterial pressure falls below 100 mmHg, nervous reflexes: (4)
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
27
What factors determine blood flow?
Pressure difference between the two ends of a vessel (pressure gradient) Impediment of blood flow through the vessel (resistance)
28
How do we calculate the flow through a vessel?
F = deltaP/R
29
Flow is _______ (directly or indirectly) proportional to pressure
Directly
30
Flow is _______ (directly or indirectly) proportional to resistance
Indirectly
31
Laminar blood flow = ?
Streamline flow
32
What are the characteristics of laminar blood flow?
Blood flows at a steady rate Blood vessel is long and smooth Blood flows in streamlines (layers)
33
What are the characteristics of streamline flow?
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
What are the characteristics of turbulent flow?
Nonlayered flow Creates murmurs Produces more resistance than laminar flow
35
When does turbulent flow occur?
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
Tendency for turbulent flow increases in direct proportion to:
Velocity of blood flow Diameter of the vessel Density of the blood
37
Tendency for turbulent flow increases inversely to:
Viscosity of the blood
38
The density of blood depends on what?
Proportion of its components, particularly RBCs and proteins
39
Define Blood Viscosity
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
What is the equation for Reynolds Number, what does it measure and what does each variable represent?
``` 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
What happens when Re rises above 200-400?
Turbulent flow will occur in some regions of a vessel
42
What happens when Re rises above 2000?
Turbulence will occur even in a straight vessel
43
What is the meaning of "blood pressure"?
The force exerted by the blood against any unit area of the vessel wall
44
How can pressure be measured?
With a mercury manometer or with electronic transducers
45
Define Resistance
The impediment to blood flow in a vessel
46
How must Resistance be calculated?
It must be indirectly calculated from measurements of blood flow and pressure R = Pressure/(volume/time)
47
List the three major variables that determine resistance
Vessel Radius (most important variable) Blood Viscosity Vessel Length
48
If blood flow decreases, what happens to resistance?
Resistance increases
49
If upstream pressure increases, what happens to resistance?
Resistance increases
50
If downstream pressure increases, what happens to resistance?
Resistance decreases
51
Know relationship of variables in this equation: | R =8ηl/πr^4
``` R = resistance η = viscosity of blood l = length of vessel r^4 = radius of BV to the 4th power ```
52
Why is there a low pressure drop across major arteries?
Because they have a low resistance
53
Where is the largest pressure drop and why?
Largest pressure drop is across arterioles b/c they have the highest resistance
54
Systolic pressure is the _______ (highest/lowest) arterial pressure during a cardiac cycle.
Highest
55
Diastolic pressure is the ________ (highest/lowest) arterial pressure.
Lowest
56
Define Pulse Pressure
Difference between systolic and diastolic pressure
57
What is the rate of blood flow through the entire circulatory system?
Cardiac output | 100 ml/sec
58
What is the pressure difference from systemic arteries to systemic veins?
100 mmHG
59
Using 100 mmHg for the pressure and 100 ml/sec for the rate of flow, what is the resistance of the entire systemic circulation?
100/100 = 1 PRU
60
What happens to the PRU in conditions where the vessels are strongly constricted?
Total peripheral resistance may rise to 4 PRU
61
What happens to the PRU in conditions where the vessels are greatly dilated?
The resistance can fall to as little as 0.2 PRU
62
What is the average mean pulmonary arterial pressure?
16 mmHg
63
What is the average mean left arterial pressure?
2 mmHg
64
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?
14/100 = 0.14 PRU
65
Define Conductance
Measure of blood flow through a vessel for a given pressure difference
66
Conductance is the exact reciprocal of _____
Resistance | Conductance = 1/Resistance
67
Conductance is ______ (directly/indirectly) proportional to diameter^4
directly
68
Poiseuille's Law
F = πΔPr4/8ηl
69
Arterioles, capillaries, venules, and veins are arranged in ________ (parallel/series)
Series
70
Blood vessels branch extensively to form parallel circuits. For BVs arranged in parallel the total resistance to blood flow is expresses as:
1/Rtotal = 1/R1 + 1/R2 + 1/R3.... Therefore, total resistans is far less than the resistance of any single BV
71
What is the total conductance for vessels arranged in parallel?
The total conductance for vessels arranged in parallel is the sum of the conductance of each parallel pathway
72
List the circulation arranged in parallel
Brain, Kidney, Muscle, Gastrointestinal, Skin, Coronary Circulation (Each of the above tissues contributes to the overall conductance of the systemic circulation)
73
Amputation of a limb or removal of a kidney removes a parallel circuit resulting in:
Reduced total vascular conductance Reduced total blood flow Increased total peripheral vascular resistance
74
Define Viscosity
Measure of the fluid's internal resistance
75
What is the relationship between viscosity and resistance?
Greater the viscosity, greater the resistance
76
What is the prime determinant of blood viscosity?
Hematocrit
77
What happens to viscosity when a person has anemia?
Anemia decreases viscosity
78
What happens to viscosity when a person has polycythemia?
Polycythemia increases viscosity
79
Define Blood Flow Autoregulation
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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