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29 Cards in this Set
- Front
- Back
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True/False: Metarterioles contain precapillary sphincters
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TRUE--composed of smooth muscle
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How is capillary blood flow controlled?(two mechanisms)
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Arteriole constriction and rings of smooth muscle around precapillary sphincters
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What is a capillary's wall made of?
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Single layer of endothelial cells
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What are the three types of capillaries?
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Continuous(most tissue), Fenestrated(many pores and seen in kidneys and small intestines), and Sinusoidal(large pores and incomplete basal membrane seen in marrow and liver)
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How do water soluble substances get through the capillaries?
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Through the pores
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What increases capillary permeability? Where in the body are the capillaries largely impermeable?
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Histamine--BBB(tight junctions)
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The main transport process across capillaries is what? How are small proteins moved?
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Diffusion--vesicular transport
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Do large proteins cross the capillaries?
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No
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What is found between endothelial cells in a capillary?
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Cleft held together by loos reticular fiber
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What are the two pressures that cause movement of fluid in a capillary?
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Hydrostatic and osmotic
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What happens in the capillaries during arteriolar constriction?
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Decrease in hydrostatic pressure across the capillaries and fluid is brought back into the capillary--happens during BLOOD LOSS OR HEMORRHAGE
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What happens in the capillaries during venous pressure goes up?
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Edema
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What happens in the capillaries during hypoproteinemia?
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Fluid moves out
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What happens in the capillaries during Dehydration?
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Fluid moves back into circulation
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How are lymph vessels like veins?
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One way valves and depend on skeletal muscle movement
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How are insoluble proteins that can't cross capillaries transported?
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IN THE LYMPH
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What two scenarios lead to edema?
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Forces of filtration are greater than forces for reabsorption--Inadequate reabsorption
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When does edema occur(in terms of pressure)?
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When hydrostatic pressure is 30% above normal
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Why is myoglobin needed in the heart?
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Because during systole blood can't perfuse so it has to store oxygen during diastole
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What are the major determinants of myocardial oxygen consumption?
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HR, aortic pressure, and inotropy
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What is an important regulator of blood flow?
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Nitric Oxide
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What happens to coronary vessels during increased activity?
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They sense the buildup of metabolites and vasodilate
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What do oxygen and adenosine do in the heart?
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Oxygen causes vasoconstriction at high levels in the coronaries--Adenosine causes vasodilation and binds to the receptors on vascular smooth muscle and decreases calcium entry into the cell
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What adjusts the arterioles in skeletal muscle?
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Symp constriction at rest and metabolic vasodilation during activity
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What controls skin circulation?
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Symp--cold = constriction
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Which is more important--sweating or dermal circulation?
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DERMAL CIRCULATION
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What preserves blood flow in the brain?
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The circle of Willis and high capillary density
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What are two brain adaptations that keep it perfused with oxygen?
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Cerebral vessels are excused from baroreflex vasoconstriction and the brain tissue is very sensitive to changes in CO2
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What happens in pulmonary circulation in response to CO2 and O2 levels changing?
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In pulmonary circulation, a decrease in O2 and and increase in CO2 levels will cause constriction--with increased O2 and decreased CO2, pulmonary arterioles will dilate
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