regional circulation

Question 1

part of heart at greatest risk for ischemic damage

Answer 1

endocardium

Question 2

estimation of work done by heart

Answer 2

work = myocardial O2 consumption
est using rate-pressure product (RPP)
RPP = HR x SystolicBP
inc HR or SBP cause heart to work harder

Question 3

how do you meet increased O2 demands in the heart?

Answer 3

increase flow

heart extracts large % of O2

Question 4

splanchnic circulation

Answer 4

in series (R’s add up)
hepatic portal system - nutrients go to portal sys for detox in liver
highly innervated by SNS
recieves lrg % of CO at rest = reservoir of blood

Question 5

counter-current exchange

Answer 5

intestinal villi
allows venule to steal O2 from the ascending arteriole
in low O2 conditions, can cause anoxic damage to villi (ie heart failure & inc SNS act)

Question 6

3 reasons cutaneous circ is effective in dispersing heat

Answer 6

1) out layers are close to ambient temp - > lrg temp gradient bet blood and environ
2) capillaries greatly inc surface area
3) slow velocity = max time for heat exchange

Question 7

apical skin

Answer 7

hand, feet, ears, nose
AV anastomoses
SNS - constriction (maintain heat)
passive dilation

Question 8

nonapical skin

Answer 8

SNS ->NE - constriction

Ach -> sweat glands release Bradykinin -> vasodilation of cutaneous vasculature

Question 9

skeletal muscle circularion

Answer 9

Major site of peripheral vasoconstriction
secondary pumping system for veins
lowers venous pressure => aid in capillary perfusion

Question 10

reactive hyperemia

Answer 10

phenomena of skel mm
interruption of Q -> buildup of vasodilating metabolites -> Q restored => Q inc due to vasodilation until metabolites are washed away

Question 11

cerebral circulation

Answer 11

uses SNS to reduce/stop supplies to other organs
Brain & Heart:
extracts high % of O2
low capability for anaerobic respiration
high cap for Autoregulation
immune to nervous sys imput

Question 12

blood-brain barrier

what can cross?

Answer 12

tight-junctions
trans-cellular crossing: O2, CO2, Alcohol
Glucose - GLU1 transport

Question 13

Autoregulation in the brain

Answer 13

maintains steady flow rates in the face of changing arterial pressures
doesnt cope well w interruptions in O2 supply
extracts most of O2
range - 60-130mmHg
chronic hypertension shifts autoreg curve to the right

Question 14

20-30% decrease in cerebral flow

40-50% decrease in cerebral flow

Answer 14

lightheadedness
fainting (syncope)

Question 15

Partial Pressure CO2 and brain

Answer 15

slight Inc PCO2 –> BIG inc in cerebral Q (note responding to H+ not actual CO2 levels)
dec PCO2 -> no response until PCO2<50 then vasodilation occurs and Q increases

Question 16

cerebral perfusion pressure

Answer 16

CPP = MAP - ICP
constrained space => regional changes in BP
Inc intercranial pressure:
- veins collapse
- dec CPP (the force) = dec Q