Circulation & Hemodynamics II Flashcards

1
Q

What are the components of microcirculation?

A

arterioles w/ smooth m walls

meta-arterioles w/ limited smooth m walls

capillaries w/ pre-capillary sphincters

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2
Q

What moves thru clefts in capillary wall?

A

passage of water soluble substances (glucose, electrolytes)

small in brain & large in liver/gut

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3
Q

What moves thru capillary endothelial cell wall?

A

lipid soluble substances (O2 & CO2)

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4
Q

What is the Starling equation?

A

calculates the flow of water either out of capillary (+) or drawing it into the capillary (-)

dependent on net forces influencing movement of water

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5
Q

What are the 2 forces found on both sides of capillary wall?

A

hydrostatic pressure & osmotic pressure

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6
Q

Where does the fluid from gradual leakage out of capillary end up?

A

gathered by lymphatic system & returned to venous circulation

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7
Q

Starling equation

A

Jv = Kf [(Pc + i) - (Pi + c)]

or

Jv= Kf [(Pc - Pi) - (c-i)]

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8
Q

What does a positive Jv indicate?

A

predicts a net movement of fluid out of capillary

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9
Q

What can alter these forces?

A

Pc affected by elevated venous pressure (heart failure)

Pi affected by restricted lymphatic flow or increased driving force out of capillary

c is altered by decrease in albumin (starvation, liver failure)

i is altered by restricted lymph flow or inflammation

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10
Q

What is local control of circulation?

A

local beds have an ability to break from central/autonomic control if need becomes greater than is being allowed

will not usually significantly alter TPR

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11
Q

Myogenic Control (autoregulation)

A

if BP is elevated, arterial walls become stretched & causes vasoconstriction

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12
Q

Metabolic control

A

in active & reactive hyperemia

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13
Q

Active hyperemia

A

increasing interstitial conc of metabolites (CO2, H+, K+, lactate & adenosine) or reduction of O2 b/c increasing metabolic demand

causes smooth muscle of vasc to relax & increase flow thru area

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14
Q

Reactive hyperemia

A

when vascular obstruction causes build-up of metabolites & leads to vasodilation

if obstruction is removed, area will be flooded w/ blood

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15
Q

Shear (method of local control)

A

if vascular bed dilates due to metabolic demand, flow thru upstream arterioles & small arteries would increase

this would increase shear (wall friction) leading to release of NO which would cause vasodilation & augment downstream metabolic effect

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16
Q

Examples of neural & hormonal control of blood flow

A

sympathetics
histamine & bradykinin
serotonin
prostaglandin

17
Q

Effect of sympathetics

A

vasoconstriction (if decreased stimulation=vasodilation)

18
Q

Effect of histamine & bradykinin

A

arteriolar vasodilation

increases Kf (allowing escape of large molecules)

causes edema in response to tissue damage

19
Q

Effect of serotonin

A

vasoconstriction in response to tissue damage

20
Q

Effect of prostaglanin

A

mixed!

21
Q

Coronary Circulation

A

LARGELY metabolic control

LV contraction causes constriction of vasculature (near endocardial surface)

22
Q

Cerebral Circulation

A

largely metabolic control (responds to increase CO2)

23
Q

Pulmonary Pressure

A

avg pressure is up to 20 in pulmonary A (highest pressure of pulm vascular system in RV & pulm A)

24
Q

What is the resistance of the pulmonary vasculature compared to systemic circulation?

A

lower resistance (about 1/10)

25
Q

Regulation of Pulmonary Blood Flow

A

vasoconstriction to alveolar hypoxia so directs blood to areas receiving O2

little sympathetic influence

26
Q

How do pulmonary arteries differ from systemic?

A

arterial system of lungs is more compliant so small changes in mean pressure will significantly dilate arteries

reduces resistance & helps maintain low pressure even w/ large changes in flow

27
Q

Skeletal Muscle Circulation

A

@ rest-under central baroreceptor control

when active-comes under local control

28
Q

How are adrenal glands involved in flight response?

A

secrete epi which bind B2 receptors & causes vasodilation

29
Q

How does BP stay constant when skeletal m is active?

A

motor centers cause generalized increases in sympathetic outflow so increased CO & non-muscular vascular resistance to anticipate drop in TPR from skeletal m dilation

30
Q

Skin Circulation

A

sympathetic vasoconstriction from baroreceptor reflex

sympathetic inhibition & dilation of shunt pathways to release excessive body temperature

31
Q

What is a right to left shunt?

A

blood passing from systemic veins to systemic arteries w/o passing thru functional lung tissue

32
Q

What is a left to right shunt?

A

blood passing from systemic arteries to systemic veins w/o passing thru capillary bed for substance exchange

33
Q

Where is sympathetic innervation of vascular smooth muscle the highest?

A

highest in skin & skeletal muscle vasculature!

34
Q

What is Pc?

A

pressure inside capillary that favors filtration OUT of capillary (decreases along length of capillary so lowest Pc @ venous end)

35
Q

What is Pi?

A

pressure of interstitial fluid that opposes filtration (moving of fluid from IF to capillary)

36
Q

What is pie c?

A

capillary oncotic pressure (due to plasma proteins)

increase in protein conc of blood will decrease filtration

37
Q

What is pie i?

A

interstitial oncotic pressure that favors filtration (dependent on protein conc of interstitial fluid)