3.3.1 Regional Circulations Flashcards
Which organs require the largest amount of blood flow during rest?
Brain, Heart, Liver and Kidney
What is the equation for flow to an organ?
Why does resting blood flow differ between organs?
Resting blood flow to organs varies because of differences in vascular resistance between organs
When completely dilated which organ had the greatest increase in blood flow? Which has the least?
The skeletal muscle had the greatest increase, but heart is 5-fold.
Kidney had the lowest.
What organs rely mainly on local control of blood flow?
The heart and the brain.
What is oxygen uptake and what is the equation for it?
What can increase the oxygen uptake for an organ?
Opening of precapillary sphincter will increase the number of perfused capillaries.
What is the direct Fick Method and what is it’s equation?
Why is the heart able to consume so much more of the circulating oxygen than other tissues? How does this compare to the kidney?
What is autoregulation?
What allows for the brain and heart to maintain nearly constant flow? How does this compare to systemic organs?
What are the mechanisms for autoregulation?
What is the myogenic response and what is its pathway?
What is the metabolic hypothesis?
Vasodilator metabolites are produced by cells of many organs. Interstitial concentrations of these are determined by rate of formation and rate of removal.
What is the result of increased local metabolites? Will this change TPR significantly?
What is the role of adenosine as a vasodilator metabolite?
Adenosine levels rise wen ATP formation is impaired. Adenosine freely diffuses out of a cell and is a potent vasodilator.
How does potassium act as a vasodilator metabolite?
Potassium plays a major role in local regulation of blood flow in electrically organ such as the brain and heart. When the frequency of action potentials increases, the interstitial concentration of K+ rises. This local hyperkalemia causes hyerpolarization of arterioles within these organs, which decreases Ca++ influx to vascular smooth muscle, and causes relaxation.
How does lactic acid act as a vasodilator metabolite?
Increased interstitial levels of lactic acid and CO2 occur when O2 demand exceeds O2 availablility.
How can decreased ATP levels act as a vasodilator metabolite?
Decreased ATP (or increased ADP) leads to activation of KATP channels which increases K+ efflux, resulting in local hyperkalemia.
What are this actions of all vasodilator metabolites?
What is active hyperemia and what is its process?
Again what is active hyperemia? What are the main vasodilators?
How is exercise an example of active hyperemia?
It is an example in skeletal muscle. This will lead to formation of vasodilator metabolites and thus decreased vascular resistance
Decribe the process of the baroreflex response during exercise
What is reactive hyperemia?
This the phenomenon where blood flow is transiently increased following a brief period of ischemia. The classic example is when you cut off blood flow by a BP cuff.
What is the process of reactive hyperemia?
Decreased stretched arterioles and accumulation of local vasodilators.
What is the difference between ischemia/reperfusion vs hyperemia?
How can the brain be an example of active hyperemia?
What are the effect of changes in arterial PCO2 and PO2 on cerebral blood flow?
Increase in PCO2 will increase blood flow. Cerebral blood flow is highly sensitive to small changes in PCO2.
CBF changes very little which arterial PO2 levels change
Since the brain doesn’t seem to react to changes in PO2 within normal ranges what could explain this?
The brain is able to extract sufficient blood as low as 50mmHg. Any lower and were screwed.
Describe the sensitivity of the brain to changes in arterial CO2.
What is the relationship between myocardial O2 consumption and blood flow?
Describe the process of coronary blood flow during systole.
Describe the process of coronary blood flow during diastole
What are the determinants of myocardial O2 demand?
Inotropic state is the greatest determinant
What is something to worry about with a patient having an MI?
Microvascular injury due to ischemia/reperfusion. This will create ROS which can damage the vessels. Can also lead to release of endothelin-1
What is the process of pulmonary hypoxic arteriolar vasoconstriction?
Describe gastrointestinal circulation
How can cirrhosis lead to portal hypertension?
What is the effect of portal hypertension in splanchnic veins?
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