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5 Cards in this Set
- Front
- Back
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What increases the hearts tendency to fibrillate following myocardial infarction?
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An acute loss of blood supply to cardiac muscle causes depletion of potassium from cardiac myocytes. This increases the irritability of cardiac musculature and its liklihood for fibrillating. cardiac dilatation increases the liklihood of circus movements, and a current of injury allows electrical current to flow from an ischemic area of the heart to a normal area and can elicit fibrillation.
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What is the most likely stimulus for the growth of vessels in a solid tumor?
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Solid tumors are metabolically active, that need increased quantities of O2 and other nutrients. An important factor that can increase growth of new blood vessels is vascular endothelial growth factor(VEGF). Presumibly, a deficiency of tissue O2 or other nutrients, or both, leads to the formation of VEGF.
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If a patient has an O2 consumption of 240ml/min, a pulmonary vein O2 concentration of 180ml/L of blood, and a pulmonary artery O2 conc of 160ml/L of blood units, what is the cardiac output?
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The Fick principle for determining cardiac output can be applied here. The formula for cardiac output is O2 absorbed per minute by the lungs divided by atriovenous O2 difference. here, O2 consumption of the body is 240ml/min, and in a steady state condition, this would exactly equal the O2 absorbed by the lungs. Therefore, by inserting these values into the equation, the CO equals 12L/min.
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If the thorax of a normal healthy patient is surgically opened, what happens to the CO curve?
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Normal intramural pressure is -4mmHg. When the thorax is opened, the values of all pressures inside the chest immediately become 0mmHg, which is the atmospheric pressure. This increased pressure in the chest tends to collapse the atria and decreases the transmural pressure across each atrium. In particular, the right atrium transmural pressure gradient decreases about 4mmHg. Therefore, the CO curve shifts 4mmHg to the right.
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What is the relationship, between blood flow and vessel radius?
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Blood flow in a vessel is directly proportional to the 4th power of the vessel radius. Increasing vessel diameter by 50%(1.5 times control) would increase blood flow 1.5 to the 4th power times normal blood flow(100ml/min). Thus blood flow would increase to 100ml/min times 5.06 or app 500ml/min.
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