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CardioPulm > 12.5 C > Flashcards

12.5 C Flashcards

1
Q

What are the four major functions of microcirculation?

A
  • filtration/reabsorption
  • regulation of vascular smooth muscle activity
  • production of endothelial-derive factors
  • regulation of leukocyte trafficking
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2
Q

Which blood vessels don’t have a smooth muscle ring around them?

A

capillaries and post-capillary venules

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3
Q

When arterioles dilate, what happens to blood flow and pressure?

A

both increase

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4
Q

When arterioles dilate, what happens to filtration of fluid across the capillaries?

A

it increases

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5
Q

Arteriole tone plays a key role in regulating what two things?

A

organ blood flow and filtration

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6
Q

What are precapillary sphincters?

A

bands of smooth muscle at the beginning of capillaries which open or close to permit blood flow

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7
Q

Opening and closing of precapillary sphincters has what effect on vascular resistance within an organ?

A

negligible, resistance within an organ is dependent on arterioles

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8
Q

Post-capillary venules are an important site of what?

A
  • leukocyte trafficking

- increased vascular permeability

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9
Q

What are arteriovenous shunts?

A

shunts for blood to flow from an arteriole directly to a venule, skipping the capillaries

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10
Q

Flow through AV shunts is important for what?

A

temperature control

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11
Q

How does local vasodilation of arterioles affect the amount of filtration?

A

it increases capillary flow and pressure, thus increasing filtration

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12
Q

Local dilation or constriction of arterioles within one organ does not usually change TPR or MAP with what exception?

A

skeletal muscle

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13
Q

Increased venous pressure does what to capillary pressure?

A

it increases capillary pressure

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14
Q

How does right sided heart failure lead to systemic edema?

A

it increases venous pressure, increasing capillary pressure, increasing the rate of filtration

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15
Q

What problems can lead to decreased oncotic pressure?

A
  • liver disease impairs production of plasma proteins
  • kidney disease leads to increased excretion of plasma proteins
  • protein malnutrition impairs plasma protein production
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16
Q

When oncotic pressure is decreased, the clinical result is what?

A

edema

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17
Q

What are intercellular clefts?

A

gaps between endothelial cells, the width of which determines vascular permeability

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18
Q

How are intercellular clefts opened?

A

an increase in calcium (possibly due to histamine) causes contraction of actin/myosin in endothelial cells

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19
Q

What might trigger a calcium influx into endothelial cells?

A

histamine

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20
Q

Precapillary sphincters respond to changes in what?

A

oxygen levels

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21
Q

How do precapillary sphincters respond to changes in tissue oxygen levels?

A

they open in response to locally produced dilators which accumulate in tissue when blood flow is not sufficient to meet metabolic demand

22
Q

Opening of precapillary sphincters has what effect on filtration?

A

increases total surface area for exchange and increases filtration

23
Q

What is vasomotion?

A

the opening and closing of precapillary sphincters

24
Q

What is bulk flow?

A

a mechanism using pressure differences for moving substance over longer distances than diffusion is efficient for

25
Q

Why is edema problematic?

A
  • it increases interstitial volume, increasing the distance nutrients must diffuse between capillaries and cells
  • it also increases interstitial pressure, compressing venules, increasing venule resistance and decreasing blood flow
26
Q

Calcium has what effect on vascular tone?

A

it causes vasoconstriction

27
Q

Through what mechanism are cytosolic calcium concentrations decreased in endothelial cells?

A

Ca ATPase pumps

28
Q

How does vascular smooth muscle contraction differ from skeletal muscle contraction?

A

the rate is slower allowing vascular smooth muscle to maintain sustained vascular tone

29
Q

What accounts for the sustained tone of vascular smooth muscle?

A

a lower Ca ATPase activity

30
Q

Changes in cytosolic calcium are more dependent on what source of calcium, intracellular stores or influx of extracellular ions?

A

extracellular ions

31
Q

Why do calcium channel antagonists function to treat some forms of hypertension?

A

because they limit smooth muscle contraction by limiting the influx of extracellular calcium ions

32
Q

How does NE action on vascular smooth muscle cause contraction?

A

it stimulates alpha-1 receptors which opens calcium channels and increases calcium influx

33
Q

What is the effect and mechanism of effect of epinephrine on vascular smooth muscle in skeletal muscle?

A
  • circulating epinephrine binds beta-2 receptors in skeletal muscle
  • this increases activity of the calcium-ATPase pump
34
Q

What experiment demonstrated that endothelial cells are more than a passive barrier?

A
  • aortic rings with and without endothelial cells placed in a bath of ACh
  • with endothelium, the smooth muscle had less contractile force
35
Q

Endothelial-derived relaxing factor is another name for what compound?

A

nitric oxide

36
Q

How does endothelial cell damage lead to ischemia?

A

damaged endothelial cells produce less NO, so vasoconstriction predominates leading to ischemia and tissue injury

37
Q

NItric oxide synthase activity in endothelial cells is triggered by what?

A

calcium influx into endothelial cells

38
Q

An increase in calcium levels in endothelial cells causes ____ while an increase in vascular smooth muscle cells causes _____.

A

vasodilation; vasoconstriction

39
Q

What is L-NAME?

A

a competitive inhibitor of NO synthase that limits NO production by endothelial cells

40
Q

How does NO protect endothelial cells?

A

by limiting leukocyte adhesion and thereby limiting leukocyte secretion of substances toxic to endothelial cells

41
Q

L-NAME has what effects on vascular tone and vascular permeability?

A

since it inhibits NO production, it will increase vasoconstriction and leukocyte adhesion/permeability

42
Q

How does NO function in the vascular system?

A
  • vasodilator
  • inhibit leukocyte and platelet adherence
  • maintains normal low vascular permeability
  • antioxidant
43
Q

What two substance produced by endothelial cells inhibit aggregation of platelets?

A

NO and prostacyclin

44
Q

Endothelin-1 production occurs in response to what?

A

in response to endothelial cell damage

45
Q

What is the effect of endothelin-1?

A

increase calcium concentrations in smooth muscle causing sustained vasoconstriction

46
Q

What is unique about the vasoconstriction caused by endothelin-1?

A

it is sustained for a very long time (hours)

47
Q

A classic example of ischemia/reperfusion is what medical procedure?

A

organ transplant

48
Q

The ROS created during ischemic reperfusion have what effects?

A
  • direct damage to endothelial cells
  • inactivation of NO
  • increase formation of endothelin-1
49
Q

What is the harm associated with giving an IV of NO?

A

it would vasodilate the whole system and causing a decrease in TPR and therefor shock

50
Q

What is the harm associated with administering NO locally during an ischemic attack?

A

it would vasodilate the local arterioles, increasing pressure in the capillaries and cause edema

CardioPulm (31 decks)

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