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<3 > Circulation And Hemodynamics > Flashcards

Circulation And Hemodynamics Flashcards

1
Q

What is

Cardiac Output?

A

Rate at which blood is pumped from either ventricle

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2
Q

What is

Venous Return?

A

Rate at which blood is returned to atria from veins

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3
Q

What will CO equal in steady state?

A

VR

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4
Q

How is the CO of the Left Heart distributed among organ systems?

A

Via set of parallel As.

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5
Q

What percentage of CO is distributed and to where?

And thru what As.?

A

15 % —> brain via cerebral as.

5% —> heart via coronary As.

25% —> kidneys via renal As.

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6
Q

How can you change blood flow to an organ system? (3)

A
  1. CO = constant, by blood flow redistributed
  2. CO = increases or decreases, % distribution = constant
  3. both CO and % distribution
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7
Q

What are the characteristics of

Arteries?

A
  • under high pressure
  • small percentage of the blood volume
  • Thick walled w/ extensive development of elastic tissue, Sm. M., and CT
  • contain the Stressed VOlume
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8
Q

What is Stressed Volume?

A

Volume of blood in arteries

under High Pressure

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9
Q

What are the characteristics of Arterioles?

A
  • moderate pressure, smooth muscle walls can contract to control flow
  • SM m. In walls

-innerv. By Symph. Adrenergic w/
Alpha-1 Rs.=will constrict
-Beta-2 = will dilate

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10
Q

What are the characteristics of veins?

A
  • under low pressure
  • contain largest percentage of BV
  • contract to move blood to As. To increase BP

-have UNstressed volume

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11
Q

What is unstressed volume?

A

Volume of blood in veins (bc blood is under low pressure)

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12
Q

What are the characteristics of capillaries?

A

Interposed b/w arteries and veins

Large x-sect. Area

Single endothelial lining

X-change of nutrients, waste, and fluid occurs across cap walls

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13
Q

What is the formula for the

Velocity of blood flow?

A

V = q/a

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14
Q

How will velocity change as diameter increases?

A

Velocity decreases

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15
Q

Why is velocity lowest in the capillaries?

A

Bc caps are highest in cross-sect.

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16
Q

What will increased viscosity due to velocity?

A

Increase viscosity = decreased velocity

Bc increased resistance —> decreased flow —> decreased velocity

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17
Q

What are murmurs?

A

Audible vibrations caused by turbulent flow

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18
Q

What is the velocity of blood flow showing?

A

Rate of displacement of blood per unit of time

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19
Q

What 2 factors determine blood flow?

A
  1. Pressure difference

2. Resistance

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20
Q

What is the formula for

Blood flow?

A

Q = change(P) / R

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21
Q

What will happen to Q as resistance increases?

A

Decreased flow

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22
Q

How would you solve for resistance of entire systemic vasculature or in a single organ/blood vessel?

A

R = change (P) / Q

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23
Q

What is total peripheral resistance?

A

Resistance of entire systemic vasculature

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24
Q

What is the formula for

Total peripheral resistance?

A

TPR = (Paorta - Pvena cava) / CO

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25
Q

What does the Poiseuille equation determine?

A

Determines resistance to flow and its relationship to blood vessel diameter and blood viscosity

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26
Q

What is the poiseuille equation dependent on?

A

If blood flow is sequential or in parallel

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27
Q

What is the formula for

Resistance to Blood flow?

A

R = 8nl / (pi)(r^4)

n = viscosity of blood 
l = length of blood vessel
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28
Q

How would an increase in viscosity occur?

A

Hematocrit increase

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29
Q

How much would resistance increase with 75% occlusion of artery?

A

Resistance increase by 256 fold

Bc 1/ (1/4^4) = 256

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30
Q

What is “series” resistance in blodo vessels?

How would you then calculate R?

A

‣ Total resistance of system arranged in series = sum of individual resistance

• R(total) = R(artery) + R(arterioles) + R(capillaries) + R(venules) + R(veins)

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31
Q

In series, how is flow and pressure affected?

A

Flow is the same at each levels

Pressure will decrease

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32
Q

Where is the greatest decrease seen in a Series system?

A

In arterioles bc they contribute the largest portion of resistance

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33
Q

Where is parallel resistance seen?

A

In major arteries branching off aorta (renal, cerebral, coronary)

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34
Q

How is the total resistance in parallel compared to individual resistances?

A

Total resistance is much less

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35
Q

What is the formula for

Parallel Resistance ?

A

1/R(total) = 1/(R1) + 1/(R2) + 1/(R3) etc.

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36
Q

How is the flow and pressure affected by Parallel Resistances?

A

Flow is decrease, but pressure is not lost

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37
Q

If resistance of one vessel in parallel increases, how is total resistance affected?

A

Total resistance increases

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38
Q

What is laminar flow?

What is the velocity at the
Vessel wall &
Center?

A

Streamline flow with a smooth parabolic profile

Velocity at vessel wall = center
Velocity at center = maximal

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39
Q

What is turbulent blood flow?

A

Streams are mixed radially and axially and energy is wasted

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40
Q

What will turbulent flow cause?

A

Audible flow w/ Korotkoff sounds or murmurs

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41
Q

What are some causes of turbulent flow?

A

Blood vessel stenosis

CV disease

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42
Q

What is the Reynolds number used for?

A

To predict whether blood flow will be laminar or turbulent

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43
Q

What is the formula for Reynold’s number?

A

N = pdv / n

p = density 
n = viscosity
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44
Q

If Reynolds # is less than 2000 - what kind of flow is it?

A

Laminar

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45
Q

If Reynolds # Is over 2000 - what kind of flow is it?

A

Turbulent

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46
Q

If viscosity decreases how is Reynolds # affected?

A

Increased

Moving toward turbulent

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47
Q

If the diameter of the vessel narrows, how is Reynolds # affected?

A

Increased

Moving toward turbulent

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48
Q

What can Anemia cause?

A

Functional murmurs bc turbulent flow

Bc decreased hematocrit = decreased viscosity = increased Reynolds #

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49
Q

How do Thrombi affect Reynolds #?

A

Blood clots will narrow vessel diameter and increase blood velocity

—> increase in Reynolds #

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50
Q

Why is the mean pressure high in the aorta? (2)

A
  1. Large volume of blood pumped form LV

2. Low compliance of arterial wall

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51
Q

The pulsatile pressure seen at the aorta reflect what?

A

Pulsation activity of heart

Ejection of blood during systole, resting during diastole

52
Q

Where will pulsing pressures stop being seen?

A

In arterioles

53
Q

What is the formula for pulse pressure?

A

Systolic - diastolic

54
Q

How does compliance affect pulse pressure?

Why?

A

Increases it

Bc systolic pressure increases (need higher pressure to pump out), but diastolic stays the same

55
Q

What is the mean arterial pressure?

A

Average pressure in complete cardiac cycle

56
Q

What is the formula for

Mean arterial pressure (MAP)?

A

MAP = Diastolic + 1/3 (Pulse pressure)

57
Q

What is arteriosclerosis?

A

• Build-up of plaque deposits in arterial walls decrease diameter of arteries and make them stiffer and less complaint

58
Q

How does arteriosclerosis affect

  • systolic pressure
  • pulse pressure
  • mean pressure?
A

Systolic = increased

PUlse pressure = increased

Mean pressure = increased

(Will not change shape)

59
Q

How does aortic stenosis affect MAP?

A

Narrowed aortic valve = less SV from LV to aorta

= systolic p. = decreased
= pulse p. = decreased
= mean pressure = decreased

60
Q

How does pressure in the pulmonary vasculature differ from systemic?

A

Lower than systemic

61
Q

How is Venous pressure?

A

Low pressure, high compliance, large volume

62
Q

How is atrial pressure estimated?

A

By pulmonary wedge pressure

63
Q

What does the pressure at the Left atrium determine?

A

Extent of cardiac failure

We measure there bc if there is no blood/pressure there = no blood out to body

64
Q

What does the compliance of blood vessels mean?

A

Volume of blood a vessel can hold at a given pressure

65
Q

What is the formula for

Compliance of Blood vessels?

A

C = V/P

66
Q

What happens to compliance w/ age?

A

Less compliant w/ age bc..

Arterial walls become stiffer and less distensible

67
Q

For an old artery to hold the same volume as a young artery, how should the pressure be?

A

Much higher in old than young

68
Q

What is microcirculation?

A

Refers to function of the smallest blood vessels (caps and neighboring lympahtic vessels)

69
Q

What is the function of capillaries?

A

‣ Sites of exchange of nutrient and waste products in tissues and site of fluid exchange b/w vascular and interstitial compartment

70
Q

What is the flow from arterioles to caps?

A

Arterioles —> meta-arterioles —> capillaries

71
Q

What are precapillary sphincters?

What is their function?

A

Band of Sm. M.

Open and close and determine blood flow to capillary bed

72
Q

How does exchange occur across cap walls?

A

By simple diffusion

73
Q

What does the rate of diffusion thru/between cap cells depend on?

A 
Driving force (partial pressure) 
Surface area available
74
Q

How does water soluble substances get across cap walls?

A

Diffuse in the aqueous clefts between endothelial smells

• So, surface area for their diffusion = less than that for the lipid soluble gases

75
Q

What are the factors for fluid transfer across Cap Walls?

A

Osmosis driven by

  1. Hydrostatic pressure
  2. Osmotic pressure
76
Q

How can proteins cross into caps?

A

Thru fenestrated caps or in pinocytotic vesicles

77
Q

What is the effective osmotic pressure contributed by protein in Caps called?

A

Colloid osmotic pressure or

ONCOTIC pressure

78
Q

What does the Starling equation tell us?

A

Fluid movement across capillaries

79
Q

What is the formula for the

Starling Eq. ?

A

J = Kf [(pc + (pi)i)] - [(Pi + (pi)c)]

80
Q

What if Kf in the starling equation?

A

Hydraulic conductance (mL/min per mm Hg)

‣ Water permeability of the capillary wall

81
Q

What is Pc in the Starling Eq.?

A

Capillary hydrostatic pressure (mm Hg)

‣ force favoring filtration out of capillary - favors out

82
Q

What is Pi in the starling Eq.?

A

Interstitial hydrostatic pressure (mm Hg)

‣ Force opposing filtration out of capillary - favors in

83
Q

What is (pi)c in the starling Eq.?

A

Capillary oncotic pressure (mm Hg)

‣ Force opposing filtration out - favors in

84
Q

What is (pi)i in the starling equation?

A

Interstitial oncotic pressure (mm Hg)

‣ Force favoring filtration- favors out

85
Q

What are the characteristics of lympahtic capillaries ?

A

lie close to vascular capillaries

◦ Have one way flap valves - permit interstitial fluid and protein to enter but not leave capillaries

86
Q

What will the lympahtic capillaries merge eventually into?

A

The thoracic duct

87
Q

How is lymph pushed back to Thoracic duct?

A

Compression of lymph vessel by activity of surrounding sk. M.

And

by contraction of smooth m. In lymph vessels

88
Q

How many liters of lymph are recycled/day?

A

2-3 liters/day re-enters at subclavian v.

89
Q

What is Edema?

A

Increase in interstitial fluid volume

90
Q

How is edema formed? (2)

A

When there is increased filtration

Or

When lympahtic drainage is impaired

91
Q

How can Pc cause increased filtration?

A

If Pc is increased ==> increased filtration (favors out)

Increased if elevated venous pressure (heart failure)

92
Q

How can pi(C) cause increased filtration?

A 
Decrased pi(c) ==> increased filtration 
(Favors in so you would want it to decrease)

Decrease due to decrease in albumin due to starvation or liver failure

93
Q

How can Kf cause increased filtration?

A

If increased

Can be increased due to

  • cap wall destruction
  • burn
  • inflammation (release of histamine, cytokines)
94
Q

How does Pi increase filtration?

A

If restricted = increased filtration

Pi favors in so you would want it decrased

95
Q

How can lymphatic drainage be impaired and what would this lead to?

A

Would lead to edema

Impaired due to…

  • removal or irradiation of lymph nodes
  • standing (no sk. M. Compression of lymphatics)
  • parasite infection of lymph nodes
96
Q

How does sympathetic control alter resistance?

A

Can stimulate resistance beds and increase it

97
Q

What is local control of circulation for?

A

Primary mechanism is utilized for matching blood flow to the metabolic needs of a tissue

98
Q

What vasoactive substances have effects on circulation?

A

Histamine and bradykinin = vasodilation of arterioles

99
Q

What are the 3 ways local control of blood flow occurs?

A
  1. Auto-regulation (myogenic)
  2. Active hyperemia
  3. Reactive hyperemia
100
Q

What is autoregulation in local control of blood flow?

What organs use this mechanism?

A

‣ Maintenance of constant blood flow to organ in face of changing arterial pressure

‣ Organs who do this:
			• Kidney
			• Brain
			• Heart
			• Skeletal m.
101
Q

What is the myogenic hypothesis?

A

• When vascular smooth muscle is stretched, it contracts.
Thus if arterial pressure is suddenly increased, arterioles are stretched and sm. M. Will contract in response

• Contraction causes constriction —> increased resistance —> constant blood flow

102
Q

What is Active hyperemia in Local control of blood flow?

A

Metabolic control

‣ Blood flow to an organ is proportional to its metabolic activity

103
Q

What metabolites have to increase their interstitial concentration, in order for the metabolic rate to increase?

What one will decrease and cause icnreased metabolic rate?

A

CO2

H+

K+

Lactate

Adenosine

(O2 - decreases)

104
Q

How does an increased metabolic rate affect local control of blood flow?

A

‣ Causes Sm. M. Of Arterioles, metarterioles, and pre-capillary sphincters to relax —> increase flow thru arteries

105
Q

What is an example of active hyperemia?

A

Strenuous exercise

106
Q

What is reactive hyperemia in the Local control of Blood flow?

A

‣ Increase in blood flow in response or reacting to a prior period of decreased blood flow

  • When a vasuclar obstruction causes build of of metabolites leading to vasodilation
  • When obstruction is remove, area is filled with blood
107
Q

What is an example of reactive hyperemia?

A

When you sit on your hand

108
Q

What is coronary circulation most sensitive to?

A

PO2 and adenosine

109
Q

What is cerebral circulation most sensitive to?

A

PCO2

110
Q

What is ANP?

A

Vasodilator that is secreted by atria in response to increased atrial pressure

111
Q

What are the effects of Angiotensin II and Vasopressin?

A

VasoCONSTRICTORS that increase TPR

112
Q

What is the metabolic hypothesis?

A

‣ O2 delivery to a tissue can be matched to O2 consumption of tissue by altering resistance of Arterioles, in turn altering blood flow
‣ As a result of metabolic activity,
• Tissue produce various vasodilator metabolites
◦ CO2, h+, K+, lactate and adenosine

113
Q

What is shear?

A

◦ Consequence of fact that blood travels at different velocities w/in blood vessel

(If at same velocity - no shear)

114
Q

Where is shear highest at?

A

At blood vessel wall

115
Q

Where is shear lowest at?

A

Center of blood vessel

116
Q

How does shear contribute to vascular tone?

A

Dilation of vascular bed due to metabolic demand = increased flow

—> increased shear —> release of NO

NO causes to vasodilation and AUGMENTS DOWNSTREAM METABOLIC EFFECT

117
Q

What is the only method that reacts to downstream needs?

Example?

A

Shear

‣ Downstream there is a buildup of metabolites —> signals to vasodilates
‣ Vasodilation causes increased blood flow thru arteries prior to blockage
‣ This increase will increase the shear experienced
‣ Increased shear causes release of NO
‣ NO causes vasodilation
• Augmenting the downstream metabolic effect

118
Q

What is cerebral circulation largely controll by?

A

By local metabolites (esp. CO2)

119
Q

What does hypoxia cause re: vascular tone?

A

Vasoconstriction in pulmonary circulation

120
Q

How is renal circulation controlled?

What is it independent of?

A

Tightly AUTO-regulated so that flow remains constant even when renal perfusion press. Changes

Independent of sympathetic innervation

121
Q

What control is Sk. M. Under -

At rest?

When active?

During flight response?

A

At rest: central baroreceptor control (ne —> Alpha)

Active: under local
(Vasodilator substances)

Flight: Adrenal —> epi —> beta-2 = vasodilation

122
Q

How is COronary circulation affected by mechanical compression?

A

Mechanical compression will occur during systole in cardiac cycle

  • causes brief period of occlusion and reduction of blood flow
  • reactive hyperemia occurs
  • increased blood flow post systole
123
Q

What is Skin circulation controlled?

A

Sympathetic vasoconstriction according to baroreceptor reflex

124
Q

How is Skin circulation changed when there is excessive body temp.?

A

Sympathetic inhibition

-dilation of shunt pathways

125
Q

What are the Shunt pathways?

Examples of each?

A
  1. R —> L
    - blood passes from systemic Vs. —> As. W/o passing thru functional lung tissue
  2. L —> R
    - blood from Systemic As. —> VSD. W/o passing thru cap bed

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