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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
What lines the inner layer of the wall in all blood vessels?
endothelial cells
26
Name 3 other components of blood vessel walls.
- smooth muscle - fibrous connective tissue (collagen) - elastic connective tissue (elastin)
27
Name 2 structural features of arteries.
- large diameter | - little resistance
28
In arteries, walls contain ____ and ____ tissue. Why?
- elastic and fibrous tissue | - under high pressure
29
Name 3 features of muscular arteries.
- less than 0.1 mm in diameter - little elastin - smooth muscle regulates radius
30
What is compliance?
a measure of the relationship between pressure and volume changes
31
Low compliance in arteries means:
a small increase in volume = large increase in pressure
32
Arteries are a _____ reservoir.
pressure
33
Artery features that enable energy/pressure storage are:
- structure | - response during systole and diastole
34
How do arteries respond during systole?
expand as blood enters arteries during systole
35
How do arteries respond during diastole?
recoil during diastole
36
High compliance in veins means:
a large increase in blood volume is required to produce a large increase in pressure
37
Pressure in the aorta varies with ____ _____.
cardiac cycle
38
When is the pressure in the aorta at its maximum? Why?
- systolic blood pressure | - due to ejection of blood into aorta
39
When is the pressure in the aorta at its minimum? Why is it not 0?
- diastolic blood pressure | - not 0 due to elastic recoil
40
How is arterial blood pressure measured?
BP = SP/DP
41
What is average arterial BP?
120/80
42
Pulse pressure =
SP - DP
43
MAP =
[SP + (2 x DP)]/3
44
Why do we multiply DP by 2?
DP is twice as long as SP
45
What is average MAP?
[120 + (2 x 80)]/3 = 93.3 mm Hg
46
What is the driving force for blood flow?
MAP
47
Regulating ___ is critical to normal function.
MAP
48
MAP < normal means:
- hypotension | - inadequate blood flow to tissues
49
MAP > normal means:
- hypertension | - stressor for heart and blood vessels
50
What are the sounds heard for systolic pressure in measuring BP?
beginning of sounds
51
What are the sounds heard for diastolic pressure in measuring BP?
distinct change in sounds
52
If cuff pressure is above 110 mm Hg, what would we find?
- no blood flow | - no sound
53
If cuff pressure is between 70 and 110 mm Hg, what would we find?
- turbulent flow | - audible vibrations (Korotkoff sounds)
54
If cuff pressure is below 70 mm Hg, what would we find?
- laminar flow | - no sound
55
Arterioles are ____ vessels
resistant
56
Arterioles > ___% TPR
60%
57
What are arterioles?
- part of microcirculation | - connect arteries to capillaries or metarterioles
58
What structural feature do arterioles have to regulate pressure?
ring of smooth muscle
59
Arterioles have the largest pressure drop in vasculature, from ___ mm Hg to ___ mm Hg.
90 mm Hg to 40 mm Hg

PSIO 259 (22 decks)

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