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18 Cards in this Set
- Front
- Back
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Why is the brachial artery used for blood pressure?
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The pressure in the arm hasn't dropped significantly at this point because it's close to your heart and at the same level.
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3 steps of taking blood pressure are:
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Step 1
- inflate cuff above systolic to collapse artery and no blood flows through artery Step 2 - deflate the cuff until pressure is just below systolic pressure and vessel opens during heart beat Step 3 - slowly deflate cuff until you hear smooth flow (diastolic pressure) |
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How can you change blood resistance?
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vessel diameter - fairly easy to control resistance
vessel length - generally only when growing blood viscosity - takes a long time |
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Characteristics of elastic arteries:
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act to store potential energy in their walls due to elasticity, pressure reservoirs, very large diameter (aorta)
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Characteristics of muscular arteries
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thick, smooth muscle layer allows for vasoconstriction and vasodilation, distributing arteries, slightly smaller in diameter than elastic arteries (brachial)
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Characteristics of arterioles:
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microcirculation, extensive vasoconstriction and vasodilation, resistance vessels, function to control blood flow to certain capillary beds, largest drop in pressure occurs in these vessels
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Characteristics of capillaries
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billions, exchange vessels, nutrients and waste, porous to allow for exchange, blood cells are about the same size as capillaries to allow for maximum exchange
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What is hydrostatic pressure?
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increased pressure in either the capillary or the interstitial fluid will result in net movement of fluid; increased pressure leads to filtration and decreased pressure absorption. Pressure gradient between capillary and interstitial fluid can dictate direction of movement of fluid/ions
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What is osmotic pressure?
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Increased protein concentrations in either the capillary or interstitial fluid will result in net movement of fluid called colloid osmotic pressure, Increased protein con. leads to absorption and decreased leads to filtration, Osmotic pressure can dictate direction of movement.
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Characteristics of venules
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Blood reservoirs, next to no smooth muscle, allows some exchange here as well
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What is the metarteriole?
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Direct path from the arterial to the venule which prevents much exchange from occurring
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Characteristics of veins
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blood reservoirs, similar diameter as arteries, much thinner wall to allow pressure to continue dropping to maintain pressure gradient, one way valves, external muscles push blood back to heart
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What is mean arterial pressure and what does it do?
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The pressure at the aorta, and dictates blood flow to an organ
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What regulates mean arterial pressure?
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Baroreceptors which detect changes in vessel wall stretch. Arterial baroreceptors are in the aortic arch and in the carotid sinuses
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What do baroreceptors do?
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at the receptor they report pressure to CNS, at the heart they decrease the PNS and increase the SNS, AP of pacemakers and ventricular contractions; in the arteries they increase vasoconstriction; and in the veins the increase pressure
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What hormones do baroreceptors control?
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Epinepherine - similar response as SNS
Vasopression - vasoconstriction and decreased urine output Angiotension II - vasoconstriction, decreased urine, increased thirst |
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What happens when a vessel is damaged (platelets)?
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Platelet plug formation: platelets in the blood become activated and form first plug (adhesion). They also secrete serotonin and epinephrine to cause vasoconstriction. ADP is secreted by platelets to cause platelet aggregation but this isn't strong enough to hold for long
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What happens when a vessel is damaged (fibrin clot)
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results from a cascade of events, strong plug, stays until well healed (24-48hrs). intrinsic pathway is activated when factor XII comes in contact with collagen which initiates coagulation factors. the extrinsic pathway is activated by factor III coming into contact with plasma which works with factor VII to form joint complex which activates factor C
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