12.5 C

Question 1

What are the four major functions of microcirculation?

Answer 1

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

Question 2

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

Answer 2

capillaries and post-capillary venules

Question 3

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

Answer 3

both increase

Question 4

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

Answer 4

it increases

Question 5

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

Answer 5

organ blood flow and filtration

Question 6

What are precapillary sphincters?

Answer 6

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

Question 7

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

Answer 7

negligible, resistance within an organ is dependent on arterioles

Question 8

Post-capillary venules are an important site of what?

Answer 8

• leukocyte trafficking

- increased vascular permeability

Question 9

What are arteriovenous shunts?

Answer 9

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

Question 10

Flow through AV shunts is important for what?

Answer 10

temperature control

Question 11

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

Answer 11

it increases capillary flow and pressure, thus increasing filtration

Question 12

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

Answer 12

skeletal muscle

Question 13

Increased venous pressure does what to capillary pressure?

Answer 13

it increases capillary pressure

Question 14

How does right sided heart failure lead to systemic edema?

Answer 14

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

Question 15

What problems can lead to decreased oncotic pressure?

Answer 15

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

Question 16

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

Answer 16

edema

Question 17

What are intercellular clefts?

Answer 17

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

Question 18

How are intercellular clefts opened?

Answer 18

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

Question 19

What might trigger a calcium influx into endothelial cells?

Answer 19

histamine

Question 20

Precapillary sphincters respond to changes in what?

Answer 20

oxygen levels

Question 21

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

Answer 21

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

Question 22

Opening of precapillary sphincters has what effect on filtration?

Answer 22

increases total surface area for exchange and increases filtration

Question 23

What is vasomotion?

Answer 23

the opening and closing of precapillary sphincters

Question 24

What is bulk flow?

Answer 24

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

Question 25

Why is edema problematic?

Answer 25

- 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

Question 26

Calcium has what effect on vascular tone?

Answer 26

it causes vasoconstriction

Question 27

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

Answer 27

Ca ATPase pumps

Question 28

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

Answer 28

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

Question 29

What accounts for the sustained tone of vascular smooth muscle?

Answer 29

a lower Ca ATPase activity

Question 30

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

Answer 30

extracellular ions

Question 31

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

Answer 31

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

Question 32

How does NE action on vascular smooth muscle cause contraction?

Answer 32

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

Question 33

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

Answer 33

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

Question 34

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

Answer 34

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

Question 35

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

Answer 35

nitric oxide

Question 36

How does endothelial cell damage lead to ischemia?

Answer 36

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

Question 37

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

Answer 37

calcium influx into endothelial cells

Question 38

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

Answer 38

vasodilation; vasoconstriction

Question 39

What is L-NAME?

Answer 39

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

Question 40

How does NO protect endothelial cells?

Answer 40

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

Question 41

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

Answer 41

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

Question 42

How does NO function in the vascular system?

Answer 42

- vasodilator - inhibit leukocyte and platelet adherence - maintains normal low vascular permeability - antioxidant

Question 43

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

Answer 43

NO and prostacyclin

Question 44

Endothelin-1 production occurs in response to what?

Answer 44

in response to endothelial cell damage

Question 45

What is the effect of endothelin-1?

Answer 45

increase calcium concentrations in smooth muscle causing sustained vasoconstriction

Question 46

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

Answer 46

it is sustained for a very long time (hours)

Question 47

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

Answer 47

organ transplant

Question 48

The ROS created during ischemic reperfusion have what effects?

Answer 48

- direct damage to endothelial cells - inactivation of NO - increase formation of endothelin-1

Question 49

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

Answer 49

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

Question 50

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

Answer 50

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