Nov15 M2-Coronary Circulation Flashcards
epicardial vs intramural coronaries
intramural enter within wall. squeezed when contraction
arrhythmias main cause chemically
accum of waste products
2 organs that don’T store nutrients
heart and brain
what phase of cardiac cycle LV perfused + explanation of problems in exercise
in diastole. shortneed in exercise bc faster HR so coronary problems
organs with good flow autoregulation and goal of that
heart, brain, kidney.
if BP drops, bring it back to normal
how flow autoregulation works
dilation of small arteries and arterioles to bring R down
range of autoregulation in CPP (coronary perfusion pressure)
big range. 35-200 mmHg
2 components of flow autoregulation
metabolic and myogenic
metabolic comp of flow autoregulation
less O2 and more metabolites when BP drop makes the SM relax
myogenic comp of flow autoregulation
decreased stretch of SM bc BP drop makes it relax
Bayliss effect def
myogenic comp of flow autoregulation
what happens if increase BP and stretch across arteriole in Bayliss effect
SM constricts
2 problems in ATS
plaque that clogs arteries
endothelial dysfunction
twin epidemic in US: what 2 diseases
diabetes and obesity
endothelial dysfunction def
imbalance between vasodilating and vasoconstricitng substances produced by endoth
risk factors for endoth dysf
same as ats (age, fam history, smoking, diabetes, obesity, LDL, htn, )
what’s found on endothelium
multiple receptors (muscarinic, bradykinin, thromboxane, etc.)
2 substances produced by endothelium and important one
NO (important) (vasodilative) and endothelin (vasoconstrictive)
NO 3 effects
vasoactive (makes SM relax)
antiproliferative on SM (atheroprotective)
antithrombotic: acts on clotting cascade
what regulates NO prod
compounds binding to endothelium receptors
NO producing enzyme
eNOS (endoth NO synthase)
flow-dependent vasodilation: what
as increase perfusion P across vessel, flow increases but transmural P unchanged
how flow-dependent vasodilation works
flow leads to NO production by endoth.
makes SM relax
Ach effect on dilation
makes endothelium produce NO to relax SM
Ach testing capacity
if transmural P doesn’t drop due to Ach, means endoth dysfct
htn effect on endoth fct and expected Ach response
causes endoth dysfct. poorer Ach response
Ach normally in the blood
none
Ach effect if complete endoth dysfct
CONSTRICTION of vessels bc of muscarinic receptor on SM
normal Ach effect on vessel if inject it (2)
make endoth produce NO. NO greater effect than Ach on SM
3 organs with most O2 consumption on order
heart, kidney, brain
Fick’s principle
O2 consumption of organ = flow to that organ x arterio-venous O2 diff
how AV O2 difference changes with exercise
doesn’t change. O2 demand met with increased blood flow
coronary flow reserve + normal
CFR = max coronary flow div. resting coronary flow.
young healthy is 5
EXAM: 3 determinants of O2 consumption in the heart
HR, contractility, wall stress
wall stress
tension in wall. determined by preload (EDV) and afterload (aortic BP)
rate-pressure product def + how changes with exercise
HR x BP.
increases linearly with O2 consumption
