Microcirculation/Exchange

Question 1

Capillary Pressure (Pc)

Answer 1

hydrostatic pressure that fluid pults on the wall of the capillary

promotes outward flux of fluid

highest in the arterial end, decreases in venule side.

drives movement of fluids

Question 2

Plasma osmotic pressure (π p)

Answer 2

Osmotic pressure created by proteins, the pressure required for H2O to not move through a membrane

promotes inward flux, should be constant throughout entire capillary

Question 3

Factors increasing capillary hydrostatic pressure

Answer 3

increased blood in capillaries (artery dilation, venous constriction; arteriolar constriction/ venous pooling) —>increased Pc

Question 4

factors decreasing capillary hydrostatic pressrue

Answer 4

overall arteriolar constriction (HT) and hemorrhage

Question 5

increasing capillary osmotic pressure

Answer 5

dehydration (exs sweating)–> increased protein conc.

promotes reabsorption

Question 6

decreasing capillary osmotic pressure

Answer 6

liver failure, protein malnutrition, nephrotic syndrome, pregnancy, saline infusion

promotes filtration

Question 7

increasing IF colloid osmotic pressure

Answer 7

chronic lymph blockage, burns (increase cap perm)

promotes filtration

Question 8

factors that increase lymph flow

Answer 8

**INCREASE IN IF hydrostatic pressure (anything that favors fluid movement out of capillary into IF)

increased cap hydrostatic pressure
decreased plasma osmotic pressure
increased IF osmotic pressure
increased capillary

Question 9

coronary blood flow during cardiac cycle

Answer 9

highest during diastole because it depends on perfusion pressure at aortic openings, opening/closing of aortic valves and myocardial contraction that compresses its own vascular supply (subendocardial aa.)

Question 10

Myocardial O2 consumption at rest

Answer 10

EXTRACTION is near max at rest
blood flow paralleles myocardial metabolism
metabolic signals are key drivers of myocardial O2 delivery

Question 11

Calculating myocardial blood flow

Answer 11

MVO2=CBFX(AO2-VO2)

modified Fick equation

Question 12

Autoregulation of CBF

Answer 12

CBF is stable at wide range of MAPs

vasodilate–>decrease resistance to increase flow during exercise (stimulated when O2 demand> O2 supply) THINK EXERCISE

Adenosine, increased PCO2, No, H+ PGs

Question 13

α1 SNS

Answer 13

Epi/NE–> VC

higher expression on epicardial arteries
—> could limit backflow from endocardium during systole

Question 14

β2 SNS

Answer 14

Epi/NE—>VD

highest expression in endocardial aa.

Question 15

Rate pressure product

Answer 15

RPP=HRxSBP

gives you rough idea of O2 demand

Question 16

MI

Answer 16

severe, prolonged hypoxia damages myocardium due to atherosclerosis
–>decreased CBF—>DAMAGES SUBENDOCARDIUM FIRST

Question 17

Vasodilators

Answer 17

area after occlusion is already at max dilation, so giving VDs can just reduce cardiac work by reducing TPR