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17 Cards in this Set
- Front
- Back
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What is the normal range for urine mosm?
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75-1200
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What is considered to be hyposmotic urine?
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urine <300 mosm
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What are the 3 things you need to make hyperosmotic urine?
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1) corticopapillary gradient
a. countercurrent multiplication b. urea recycling 2) vasa recta 3) ADH |
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What are the 2 ADH stimulants?
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1) decrease in blood volume
2) deprive of water (increase osmolarity) |
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What are the 2 ADH inhibitors?
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1) alcohol
2) drink a lot of water (decrease osmolarity) |
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Why do you dilute urine before you concentrate it?
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build up concentration gradient so that ADH allows water to move out of the tubular fluid
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What determines the maximum possible urine concentration?
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the concentration at the tip of the papilla
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Does the early distal tubule (the "cortical diluting segment") participate in countercurrent multiplication?
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No - because it is not part of the loop of henle (but is does dilute the tubular fluid by absorbing solute thru the Na/Cl- cotransporter
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How do loop diuretics cause people to make dilute, less concentrated urine?
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inhibit 3-ion transporter, reducing corticopapillary gradient - cannot make concentrated urine
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What formss the CP gradient?
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1) 60% NaCl
2) 40% urea |
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How does the vasa recta keep from dissipating the corticopapillary gradient?
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1) blood flow is low
2) the vasa recta acts as a countercurrent exchanger |
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Is countercurrent exchange active or passive?
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passive
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Is there any depletion of medullary solutes in the vasa recta?
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yes, but it is slight (300 mosm at beginning, 325 mosm at end)
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What happens if the blood flow in the vasa recta increases too much?
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wash out nutrients too fast - cannot equilibrate with surrounding interstitium
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What are the ADH receptors called and where are they located?
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V2 receptors - basolateral membrane of principal cells
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Why does ADH act so quickly?
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prepackaged in principal cell and ready to go
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What mechanism does ADH work thru?
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Gs protein - AC - cAMP - PK - phosphorylation - AQP2 into membrane
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