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Human Physiology 1 -- Zach H. > 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

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

a) 1.5
b) 3
c) 38
d) 42

A

b) 3

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4
Q

What properties of arteries maintain the pressure in systemic circulation?

A

elasticity

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5
Q

What is the systolic pulmonary artery pressure that is generated by the right ventricle?

A

25 mmHg

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6
Q

What is the pulmonary diastolic pressure that remains in the right ventricle?

A

8 mmHg

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7
Q

84% of blood volume is in the systemic circulation. What percentage at any one time is found in the arteries?

A

13% is in the arteries

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8
Q

What percentage of blood in the systemic circulation is found in the systemic arterioles and capillaries?

A

7%

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9
Q

Of the total blood volume in the body, what percentage is found in the heart and lungs at any one time?

A

16% of blood volume

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10
Q

How do you calculate the velocity of blood flow (V)?

A

V = F / A

  • V is velocity of blood flow
  • F is volume of blood flow
  • A is cross-sectional area

33 cm/sec in aorta at rest (area = 2.5 cm2)
0.3 mm/sec in capillaries at rest (area = 2500 cm2)

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11
Q

The cross-sectional area of capillaries is much greater than that of any other vessel in the human body. Why is this, and why is it important?

A

Velocity of blood flow is inversely proportional to vascular cross-sectional area. Thus, the increased cross-sectional area of capillaries results in a small velocity, which in-turn slows down blood flow so that adequate exchange of nutrients and gases can occur.

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12
Q

How is cardiac output controlled?

A

Mainly by the sum of all the local tissue flows.

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13
Q

True or False:

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

A

True

*Tissue demand when they need increased blood flow. The heart has no say in which tissues get the majority of blood flow. Controlled by activation of tissues and there nutrient needs.

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14
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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15
Q

The rate of blood flow to each tissue of the body is almost always precisely controlled in relation to the tissue need. The tissue is monitored for [oxygen], other nutrients, CO2 accumulation, and tissue waste product accumulation. How does the monitoring microvessels act on local blood vessels to accommodate the tissue’s needs?

A

Act directly on local blood vessels and dilate or constrict accordingly.

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16
Q

True or False:

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

A

True

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17
Q

Since arterial pressure regulation is generally independent of either local blood flow control or cardiac output control. What reflex (control mechanism) kicks in if arterial pressure falls below 100 mmHg?

A

nervous reflexes

  • 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 important role in pressure control
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18
Q

What is a pressure gradient?

A

The pressure difference between the two ends of a vessel.

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19
Q

What is this definition describing:

“impediment to blood flow through the vessel”

A

Resistance

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20
Q

Flow through a vessel can be calculated by Ohm’s law (Poiseuille equation), what is the equation?

A

F = difference P / R

  • difference P = (P1-P2)
  • F = flow in mL/min
  • P1 = upstream pressure
  • P2 = pressure at end of segment
  • R = resistance between P1 and P2
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21
Q

Fill in the Blank:

Flow is _______ proportional to pressure difference but ________ proportional to resistance.

A

directly ; inversely

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22
Q

What is the overall blood flow (cardiac output) of an adult at rest?

A

5000 ml/min or 5 L/min

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23
Q

What are the characteristics of laminar blood flow (streamline flow)?

A

Blood flows at a steady rate

Blood vessel is long and smooth

Blood flows in streamlines (layers)

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24
Q

One of the characteristics of laminar blood flow is that the blood flows in streamlines (layers). For this, is the velocity of fluid flowing in the center or the vessel greater than that of the fluid flowing towards the outer edge, or vice versa?

A

The velocity of fluid flowing in the center is greater than that of fluid flowing towards the outer edge.

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25
Q

If laminar flow is layered (streamline) flow, then what is turbulent flow?

A

Nonlayered flow

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26
Q

True or False:

Turbulent flow produces less resistance than laminar flow?

A

False - turbulent flow produces more resistance than laminar flow.

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27
Q

Of the two different blood flows, turbulent and laminar, which one is responsible for creating heart mururs?

A

Turbulent Flow

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28
Q

What are the 4 things that cause turbulent flow to occur?

A

1) when flow is too great
2) when blood passes an obstruction within the vessel
3) when blood has to make a sharp turn
4) when blood passes over a rough surface

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29
Q

True or False:

Blood flows with greater resistance when eddy currents occur.

A

TRUE

30
Q

Tendency for turbulent flow increases when?

A

1) in direct proportion to velocity of blood flow
2) in direct proportion to the diameter of the vessel
3) in direct proportion to the density of the blood
4) inversely to the viscosity of the blood

31
Q

True or False:

Blood viscosity is the property of blood to adhere to vessel walls and to each other and is based on the number, shape, and size of red blood cells.

A

True

**relative value of blood viscosity is 4.5

32
Q

True or False:

Blood is more viscous than water.

A

True

33
Q

What effect does vessel diameter have on blood flow?

A

the greater the diameter, the greater the blood flow (ml/min)

34
Q

What is the Reynolds number?

A

The measure of the tendency for turbulence to occur.

35
Q

What is the formula to calculate Reynolds number?

A

Re = (v x d x p) / n

  • Re -> Reynolds number
  • v -> mean velocity of blood flow in cm/sec
  • d = vessel diameter in cm
  • p -> density (normally only slightly greater than 1)
  • n -> viscosity (in poise) (blood viscosity normally = 1/30 poise)
36
Q

What happens if the Reynolds number (Re) rises above 200-400 in some region of a vessel?

A

Turbulent flow will occur in some regions of a vessel.

37
Q

When the Reynolds number rises above 2000, what does this tell us?

A

The turbulence will occur even in a straight vessel.

38
Q

What does blood pressure really mean?

A

It tells us the force exerted by the blood against any unit area of the vessel wall.

39
Q

What are the two devices that can be used to measure blood pressure?

A

Mercury Manometer

Electronic Transducers

40
Q

What are the three major variables that determine resistance?

A

1) vessel radius (the most important variable)
2) blood viscosity
3) vessel length

41
Q

Of the three major variables that determine resistance, what is the most important variable?

A

Vessel Radius

42
Q

What happens to blood flow, upstream pressure, and downstream pressure if resistance is increased?

A

Blood Flow -> decreases

Upstream Pressure -> increases

Downstream Pressure -> decreases

43
Q

What happens to blood flow, upstream pressure, and downstream pressure when the resistance of a vessel is decreased?

A

Blood Flow -> increase

Upstream Pressure -> decrease

Downstream Pressure -> increase

44
Q

What is the formula for resistance?

A

R = 8nl / pie r4

R - resistance
n - viscosity of blood
l - length of vessel
r4 - radius of blood vessel to 4th power

45
Q

What characteristic does major arteries have that only allows for a low pressure drop?

A

Low pressure drop across major arteries because they have low resistance.

46
Q

When tracing blood through the systemic circulatory system and looking at pressure, which vessel has the largest pressure drop, and why?

A

Arterioles - have largest pressure drop because they have the highest resistance.

47
Q

What is the pulse pressure?

A

Pulse pressure is the difference between systolic and diastolic pressure.

48
Q

What is cardiac output and what is the average rate of CO in ml/sec?

A

CO = rate of blood flow through the entire circulatory system.

CO = 100 ml/sec

49
Q

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

A

100 mmHg

50
Q

What is the resistance of the entire systemic circulation?

A

100 / 100 = 1 PRU (peripheral resistance unit)

51
Q

Under what condition would the total peripheral resistance rise to about 4 PRU?

A

When vessels are strongly constricted.

52
Q

When vessels are greatly dilated, the resistance can fall to as little as _______PRU.

A

0.2 PRU

53
Q

What is the mean pulmonary arterial pressure?

A

16 mmHg

54
Q

True or False:

The mean left atrial pressure averages 2 mmHg.

A

True

55
Q

Complete the problem: when cardiac output is normal at 100 ml/sec, the total pulmonary vascular resistance is?

A

(16 mmHg - 2 mmHg) / 100 = 0.14 PRU

56
Q

What is the definition of conductance?

A

Conductance is the measure of blood flow through a vessel for a given pressure difference.

  • conductance is the exact reciprocal of resistance
  • conductane is directly proportional to diameter
57
Q

How do you calculate conductance?

A

conductance = 1/resistance

58
Q

What relationship to conductance explains the following statement, a fourfold increase in vessel diameter can increase the blood flow by as much as 256x?

A

Because conductance is directly proportional to diameter, thus, with only a minor change in arteriole diameter, you can have a vast increase in blood flow.

59
Q

What is the formula for Poiseuille’s Law?

A

F = (pie)(change in P)(r4) / 8nl

F - rate of blood flow (ml/min)
change in P - pressure difference between ends of vessel
r - radius of vessel
l - vessel length
n - blood viscosity
60
Q

For blood vessels that are arranged in parallel, the total resistance to blood flow is expressed mathematically as?

A

1/R (total) = 1/R1 + 1/R2 + 1/R3…..

*thus, the total resistance is far less than the resistance of any single blood vessel.

61
Q

What does the sum of the conductance of each parallel pathway tell you?

A

Total conductance for vessels arranged in parallel.

**because remember that conductance is the exact reciprocal of resistance.

62
Q

More branching blood vessels that are in parallel circuit with each other will result in lower resistance as the parallel circuit system gets larger.

A

Because the conductance will be greater, thus making the resistance less.

63
Q

Name a few of the different circulations that are arranged in parallel series within the body?

A 
Brain
Kidney 
Muscle
Gastrointestinal
Skin
Coronary Circulation
  • *Each of these tissues contribute to the overall conductance of the systemic circulation.
  • *If any of these parallel circuits are removed, then the resistance of the system will increase, thus conductance will be lowered and the total blood flow will be reduced.
64
Q

What happens to the circulatory system if a patient has an amputation of a lib or removal of a kidney?

A
  • reduces total vascular conductance
  • reduces total blood flow
  • increases total peripheral vascular resistance
65
Q

What does viscosity measure?

A

viscosity is a measure of the fluid’s internal resistance.

66
Q

What causes the viscosity of normal blood to be about 3x as great as the viscosity of water?

A

Large numbers of Suspended Red Cells

*Thus, the prime determinant of blood viscosity is the hematocrit.

67
Q

What is the average hematocrit of adult women?

A

38%

68
Q

When the hematocrit of a patient rises to around 60-70 (polycythmia), what is the viscosity, roughly?

A

about 10

69
Q

Fill in the Blank:

Anemia _______ viscosity of blood and polycythemia _______ the viscosity of blood.

A

decreases ; increases

70
Q

What is the parameter range in which tissues can adjust their vascular resistance to maintain normal blood flow through changes in arterial pressure?

A

70-175 mmHg

Human Physiology 1 -- Zach H. (12 decks)

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