B4.064 Microcirculatin and Regional Blood Flow

Question 1

what are the effects of increased ROS production

Answer 1

damage to endothelial cells
inactivation of NO
increased formation of ET-1

Question 2

effect of inactivation of NO

Answer 2

leukocyte adherence to venules

arteriolar constriction

Question 3

how was it discovered that endothelial cells have constrictive/relaxing properties?

Answer 3

exogenous ACh produced relaxation of arterial segments with endothelial cells, yet in the absence of endothelial cells, ACh caused constriction

Question 4

what vasodilator is produced by endothelial cells?

Answer 4

NO

Question 5

what are 3 examples of anti-oxidants?

Answer 5

superoxide dismutase
catalase
lipoic acid

Question 6

why are superoxide dismutase and catalase limited in effectiveness?

Answer 6

size

too large to pass into interior of cells

Question 7

why cant we give NO systemically to prevent reperfusion injury?

Answer 7

since its a potent vasodilator, this would result in dilation of arterioles throughout systemic organs
this would create a decrease in TPR and cause shock

Question 8

why cant we give NO locally into transplanted organs?

Answer 8

local arteriolar dilation would increase blood flow, increase capillary pressure, and promote edema

Question 9

what is the possible result of a microvascular brain injury

Answer 9

loss of plasma across damaged vessels > development of cerebral edema by reducing oncotic pressure gradient > reduced force of fluid reabsorption from interstitial space > edema > increased intracranial pressure and venous constriction > decreased cerebral blood flow

Question 10

what are some interventions that could help reduce cerebral edema?

Answer 10

1. hyperventilation- reduced PCO2 levels to cause cerebral vasoconstriction, this will reduce capillary pressure and reduce rate of filtration (edema)
2. mannitol- increases solute concentration in plasma, increases rate of reabsorption of fluid from interstitial space

Question 11

what is the result of lymph obstruction?

Answer 11

decreases removal of fluid and protein from interstitium > increased interstitial protein concentration > decreased oncotic resorption of fluid > edema

Question 12

what are some adverse effects of edema?

Answer 12

increased interstitial volume > increased diffusion distance between capillaries and cells > impaired exchange of metabolites between blood and tissues
increased interstitial pressure > venules and small vein compressed > increased venular resistance > decreased blood flow

Question 13

discuss the positive feedback loop of portal vein hypertension

Answer 13

portal vein hypertension > increased capillary pressure in GI organs > edema in GI organs > hypoxia > accumulation of metabolic vasodilators > dilation of arterioles > increased blood flow into portal vein > increased severity of portal hypertension

Question 14

what is another effect of portal hypertension other than edema?

Answer 14

ascites and thus decreased blood volume > production of endogenous vasopressors

Question 15

how do systolic and diastolic BP change in response to exercise?

Answer 15

decreased MAP due to lower TPR initiates a baroreflex response resulting in creased CO
low TPR: increased runoff lowers arterial diastolic P
increased pulse pressure due to increased SV
increased arterial systolic and decreased diastolic compared to normal