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PSIO 259 > Blood Flow and Pressure > Flashcards

Blood Flow and Pressure Flashcards

1
Q

What is the flow rule?

A
  • circulatory system = closed system
  • pressure = force exerted by blood
  • flow occurs from high pressure to low pressure
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2
Q

Flow =

A
  • ΔP/R
  • ΔP is the force pushing blood against various factors resisting the flow of liquid in a pipe
  • R is resistance to flow (factors that hinder flow)
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3
Q

The heart creates a _____ for bulk flow of blood.

A

pressure gradient

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4
Q

A ______ must exist throughout the circulatory system to maintain blood flow.

A

gradient

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5
Q

What are the 2 pressure gradients in the systemic circuit?

A
  • aortic pressure = mean arterial pressure (MAP)

- pressure in veins in thoracic cavity = central venous pressure (CVP)

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6
Q

What is typical MAP?

A

85 mm Hg

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7
Q

What is typical CVP?

A
  • 2-8 mm Hg (negligible)

- vena cavae = 0 mm Hg

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8
Q

ΔP (in systemic circuit) =

A

= MAP - CVP
= 85 - 0 = 85 mm Hg
- because CVP is so small, it is generally ignored; MAP = ΔP

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9
Q

What is the ΔP?

A

pressure in aorta minus pressure in vena cava just before it empties into right atrium

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10
Q

What are the pressure gradients in the pulmonary circuit?

A
  • pulmonary arterial pressure (PAP) = 15 mm Hg

- pulmonary venous pressure (PVP) = 0 mm Hg

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11
Q

ΔP (in pulmonary circuit) =

A

= 15-0 = 15 mm Hg

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12
Q

Which one is higher: ΔP in systemic circuit or ΔP in pulmonary circuit?

A

ΔP in systemic circuit

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13
Q

____ through both circuits is equal

A
  • flow

- flow = ΔP/R

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14
Q

Since flow = ΔP/R and flow through both circuits is equal, this means…

A

resistance through the pulmonary circuit is much less than resistance though the systemic circuit

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15
Q

Name 3 factors affecting resistance to flow.

A
  • radius of vessel
  • length of vessel
  • viscosity of fluid
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16
Q

Describe how the radius of vessel could affect resistance.

A

in arterioles (and small arteries), can regulate radius

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17
Q

Describe how the viscosity of fluid can affect resistance.

A
  • Viscosity of fluid = η

- blood viscosity depends on amount of RBCs and proteins: usually constant

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18
Q

What are the 2 types of regulation of the radius of arterioles (and small arteries)?

A
  • vasoconstriction

- vasodilation

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19
Q

What is vasoconstriction?

A

decreased radius –> increased resistance

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20
Q

What is vasodilation?

A

increased radius –> decreased resistance

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21
Q

What is total peripheral resistance (TPR)?

A

resistance of all blood vessels in systemic circuit

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22
Q

How does flow through network vary with resistance?

A
  • vasoconstriction in network = increased resistance = decreased flow
  • vasodilation in network = decreased resistance = increased flow
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23
Q

CO = , since ΔP = ___ and R = _____

A

= ΔP/R or MAP/TPR, since ΔP = MAP and R = TPR

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24
Q

TPR =

A

= MAP/CO
= 85/5
= 17 mm Hg per L/min (blood flow)

25
Q

What lines the inner layer of the wall in all blood vessels?

A

endothelial cells

26
Q

Name 3 other components of blood vessel walls.

A
  • smooth muscle
  • fibrous connective tissue (collagen)
  • elastic connective tissue (elastin)
27
Q

Name 2 structural features of arteries.

A
  • large diameter

- little resistance

28
Q

In arteries, walls contain ____ and ____ tissue. Why?

A
  • elastic and fibrous tissue

- under high pressure

29
Q

Name 3 features of muscular arteries.

A
  • less than 0.1 mm in diameter
  • little elastin
  • smooth muscle regulates radius
30
Q

What is compliance?

A

a measure of the relationship between pressure and volume changes

31
Q

Low compliance in arteries means:

A

a small increase in volume = large increase in pressure

32
Q

Arteries are a _____ reservoir.

A

pressure

33
Q

Artery features that enable energy/pressure storage are:

A
  • structure

- response during systole and diastole

34
Q

How do arteries respond during systole?

A

expand as blood enters arteries during systole

35
Q

How do arteries respond during diastole?

A

recoil during diastole

36
Q

High compliance in veins means:

A

a large increase in blood volume is required to produce a large increase in pressure

37
Q

Pressure in the aorta varies with ____ _____.

A

cardiac cycle

38
Q

When is the pressure in the aorta at its maximum? Why?

A
  • systolic blood pressure

- due to ejection of blood into aorta

39
Q

When is the pressure in the aorta at its minimum? Why is it not 0?

A
  • diastolic blood pressure

- not 0 due to elastic recoil

40
Q

How is arterial blood pressure measured?

A

BP = SP/DP

41
Q

What is average arterial BP?

A

120/80

42
Q

Pulse pressure =

A

SP - DP

43
Q

MAP =

A

[SP + (2 x DP)]/3

44
Q

Why do we multiply DP by 2?

A

DP is twice as long as SP

45
Q

What is average MAP?

A

[120 + (2 x 80)]/3 = 93.3 mm Hg

46
Q

What is the driving force for blood flow?

A

MAP

47
Q

Regulating ___ is critical to normal function.

A

MAP

48
Q

MAP < normal means:

A
  • hypotension

- inadequate blood flow to tissues

49
Q

MAP > normal means:

A
  • hypertension

- stressor for heart and blood vessels

50
Q

What are the sounds heard for systolic pressure in measuring BP?

A

beginning of sounds

51
Q

What are the sounds heard for diastolic pressure in measuring BP?

A

distinct change in sounds

52
Q

If cuff pressure is above 110 mm Hg, what would we find?

A
  • no blood flow

- no sound

53
Q

If cuff pressure is between 70 and 110 mm Hg, what would we find?

A
  • turbulent flow

- audible vibrations (Korotkoff sounds)

54
Q

If cuff pressure is below 70 mm Hg, what would we find?

A
  • laminar flow

- no sound

55
Q

Arterioles are ____ vessels

A

resistant

56
Q

Arterioles > ___% TPR

A

60%

57
Q

What are arterioles?

A
  • part of microcirculation

- connect arteries to capillaries or metarterioles

58
Q

What structural feature do arterioles have to regulate pressure?

A

ring of smooth muscle

59
Q

Arterioles have the largest pressure drop in vasculature, from ___ mm Hg to ___ mm Hg.

A

90 mm Hg to 40 mm Hg

PSIO 259 (22 decks)

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