You are working out really hard, but are a little dehydrated, so your pituitary gland secretes vasopressin and your blood pressure increases. How does your stomach adjust to this change compared to your biceps?
The stomach does not need more perfusion during exercise, muscles do. Consequently, the stomach blood supply will increase resistance to compensate for the change in pressure so it doesn't get more blood than it needs. Skeletal muscle, however, needs more blood and its blood supply will decrease resistance in response to the change in pressure.
What organs are really good at maintaining perfusion in the absence of neuronal activity?
Brain, heart, kidney. They are the best at auto regulation and can maintain blood flow at a perfusion pressure of 50 to 150 mmHg.
How does auto regulation look on a graph of flow and perfusion pressure when organs are injured?
Flow becomes a linear function of perfusion pressure with little auto regulation.
Why does the body sacrifice perfusion to the kidney before the heart and brain when someone is hemorrhaging?
The kidney's function is to filter blood and is largely over perfused for its function.
What are the hypothesis of auto regulation?
Myogenic (stretching the blood vessel increases Ca flux and contraction occurs, decreased stretching decreases Ca flux and relaxation occurs) and Metabolic (tissue matches blood supply with blood demand).
What are the myogenic mechanisms of auto regulation?
IONIC (stretching the blood vessel increases Ca flux and contraction occurs, decreased stretching decreases Ca flux and relaxation occurs). ENDOTHELIAL SUBSTANCES (NO, endothelial derived contracting factor (EDCF)).
What are the major assumptions of the metabolic theory of auto regulation?
1) Changes in the ratio of supply and demand of O2 in the tissue elicits a response that returns the ratio to baseline. 2) Tissue produces metabolites that cause vasodilation.
In the metabolic theory of auto regulation, how does an increase or decrease in pressure change vascular resistance?
The tissue produces a vasodilating metabolite that is washed away when there is an increase in pressure, causing vasoconstriction. It accumulates when there is a decrease in pressure, causing vasodilation.
When you are exercising, you need more oxygen to get to the muscle to accommodate for an increase in metabolic work. What is this concept called?
You are taking a patient's blood pressure and reach the point where you have occluded the artery. You then release the cuff and blood flow increases. What is this concept called?
Reactive hyperemia. There is an increase in blood flow after a period of flow restriction.
What are the possible direct vasodilator metabolites?
Oxygen, Adenosine, K+, H+, CO2 and increased osmolarity.
What happens to blood levels of adenosine as you exercise?
They increase. Adenosine is a potent vasodilator and comes out of the tissue into the blood in hypoxia, increases in blood pressure and occlusion of blood flow.
What vasodilating metabolite precedes increased levels of blood adenosine?
You have been working out really hard to the point that you will become very sore the next day. When you are working out, how do your metabolic byproducts keep blood flow up?
H+ is a vasodilator which is a product of lactic acid production and CO2 production, both metabolites during exercise.
What cells secrete molecules that are indirect and local vasodilators?
Endothelium (NO, prostaglandins, bradykinin) and mast cells (Histamine).
Which theory of auto regulation works best in the different organs of the body?
Brain, heart = vasodilator. Kidney, intestine = myogenic.