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RC Test 4 > B4.064 Prework 1: Microcirculation > Flashcards

B4.064 Prework 1: Microcirculation Flashcards

1
Q

components of the microcirculation

A 
arterioles
precapillary sphincters
capillaries
venules
arteriovenous shunts
lymphatics
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2
Q

discuss the morphology of microcirculation vessels

A

all vessels contain a single layer of epithelial cells

smooth muscle surrounds all vessels except capillaries and post capillary venules

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3
Q

effect of arteriole dilation

A

increase arteriolar radius within an organ
decrease vascular resistance in the organ
increase blood flow to the organ
increase capillary pressure
increase filtration of fluid

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4
Q

what do arterioles help regulate

A

organ blood flow

filtration by altering capillary pressure

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5
Q

function of precapillary sphincters

A 
open and close
# open determines # of perfused capillaries
determines total surface area for exchange
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6
Q

do precapillary sphincters affect vascular resistance within an organ?

A

no

determined by arterioles

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7
Q

function of capillaries

A

single layer of endothelial cells with no overlying vascular smooth muscle
sit of exchange of nutrients and fluid between blood and tissue
filtration/reabsorption: capillary pressure, oncotic pressure of plasma

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8
Q

function of post capillary venules

A

single layer of endothelial cells with no overlying vascular smooth muscle
important site of inflammation induced: leukocyte trafficking, increased vascular permeability

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9
Q

describe arteriovenous shunts

A

blood flows from an arteriole directly to a venule, skipping capillaries
flow through AV shunts is termed non-nutritional blood flow since no exchange of nutrients occurs with the tissue

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10
Q

importance of AV shunts

A

temperature regulation

primarily located in skin

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11
Q

function of lymphatics

A

under normal conditions, filtration of fluid slightly exceeds reabsorption
lymphatics remove this excess fluid and also small amount of plasma proteins which enters tissue

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12
Q

net filtration force

A

(Pc-Pi) - (Op-Oi)
hydrostatic pressure gradient - oncotic pressure gradient
c=capillary
i=interstitial

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13
Q

pressures under normal conditions

A 
interstitial pressure (Pi) about 0
interstitial protein concentration is nearly zero so the interstitial oncotic pressure (Oi) is about 0
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14
Q

what controls filtration under normal conditions

A

Pc, capillary pressure

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15
Q

what controls reabsorption under normal conditions

A

Op, plasma oncotic pressure

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16
Q

discuss the pressure gradients along a capillary

A

in first half Pc > Op so net filtration

in second half Op > Pc so net absorption

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17
Q

what is the effect of local dilation on arterioles within one organ?

A 
less pressure drop across arterioles
increases rate of inflow of blood into capillaries
increases capillary blood volume
increases capillary pressure
filtration increased
18
Q

what is the effect of local constriction on arterioles within one organ?

A 
greater pressure drop across arterioles
decreases rate of inflow of blood into the capillaries
decreases capillary blood volume
decreases capillary pressure
filtration decreased
19
Q

effect of venous pressure on capillary pressure

A

when venous pressure increases, rate of blood flow out of a capillary decreases
volume of blood in the capillary increases and capillary pressure increases
increased filtration of fluid out of the capillary into the tissue

20
Q

what are 3 causes of decreased oncotic pressure

A

liver disease: impaired production of plasma proteins
kidney disease: can increase excretion of plasma proteins in urine
protein malnutrition: impaired plasma protein production

21
Q

result of decreased oncotic pressure

A

force for reabsorption of fluid into capillaries is reduced

volume of interstitial fluid will be increased (edema)

22
Q

what is an example of an event that would increase vascular permeability?

A

exposure to an allergen

23
Q

what controls the opening of precapillary sphincters

A

open in response to locally produced dilators which accumulate in tissue when blood flow is not sufficient to meet metabolic demands of the organ

24
Q

what is the result of the opening of precapillary sphincters

A

increased capillaries perfused
increased total surface area for exchange
increased filtration

25
Q

give an overview of the lymphatic system

A

one way system that returns excess interstitial fluid to the cardio system
all lymphatic vessels converge into larger lymphatic vessels which empty into the systemic circulation via the systemic veins

26
Q

what factors influence the contractile activity of vascular smooth muscle

A 
stretch of vessels
sympathetic vasoconstrictor nerves
hormones
local factors
endothelin derived factors
27
Q

how does cytosolic calcium influence muscle activity

A

cytosolic Ca2+ concentration control cross bridging and thus vasoconstriction

28
Q

what factors regulate cytosolic Ca2+ levels

A

influx of Ca2+ through membrane channels
release of Ca2+ from sarcoplasmic reticulum
removal by Ca2+ ATPase pumps in sarcoplasmic reticulum and plasma membrane

29
Q

how does vascular smooth muscle differ from cardiac or skeletal muscle?

A

rate of cross bridge cycling is much slower due to a lower ATPase activity
vascular smooth muscle to maintain sustained tension
changes in cytosolic Ca2+ are more dependent on the influx of extracellular Ca2+ rather than release from intracellular stores

30
Q

how is NO produced in endothelial cells?

A

increases Ca2+ entry activates NO synthase

NO forms from L-arginine

31
Q

vasodilation mechanism of NO

A

highly permeable
diffuses into underlying vascular smooth muscle
decreases intracellular Ca2+ levels
causes relaxation
continuously produced in nearly all organs

32
Q

how is NO production inhibited

A

local infusion of L-name

competitive inhibitor

33
Q

functions of NO

A

vasodilator
inhibits leukocyte and platelet adherence
maintains normal low vascular permeability
antioxidant

34
Q

what is endothelin 1

A 
21 AA peptide that is not stored but is synthesized in response to various stimuli
slow process (1 hour)
formation increased following endothelial cell damage
35
Q

what is the function of endothelin 1

A

acts through membrane receptors on vascular smooth muscle cells to cause vasoconstriction by:

  1. release of intracellular Ca2+
  2. influx of Ca2+
36
Q

what is unusual about the effects of endothelin 1

A

prolonged vasoconstriction

significantly augments organ injury in conditions where endothelin 1 formation is increased

37
Q

what is ischemia

A

decreased blood flow

38
Q

what is reperfusion

A

restoration of blood flow after ischemic period

39
Q

what happens with reintroduction of O2 during reperfusion

A

generation of ROS
inactivation of NO
promotes microvascular injury

40
Q

3 primary effects of ROS

A

damage to endothelial cells > increased permeability
inactivation of NO > leukocyte adherence, constriction
increased endothelin formation > constriction and decreased flow

RC Test 4 (22 decks)

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