Regulation of Body Fluid Osmolarity - Rao Flashcards Preview

Nephrology > Regulation of Body Fluid Osmolarity - Rao > Flashcards

Flashcards in Regulation of Body Fluid Osmolarity - Rao Deck (16):
1

What does increased osmolarity stimulate in the hypothalamus?

Increased intracellular Ca -> AVP secretion
Increased thirst

2

What is the mechanism of AVP/ADH?

Vasoconstrict (V1)
V2 receptors -> Increase cAMP in collecting duct cells -> translocation of AqP-2 to lumen

3

Where is AVP degraded?

Liver
Proximal tubule

4

What is the threshold concentration for thirst?

280mOsm

5

What is nocturia a symptom of?

Decreased ability to concentrate urine

6

What is the equation of osmolar clearance?

UF * Uosm / Posm
*Normal = 2 ml/min

7

What is the equation for free water clearance?

UF * (1 - Uosm / Posm)

8

What is signified by a free water clearance = 1?

> 0 - dilute urine and concentrate plasma
< 0 - concentrate urine and dilute plasma

9

Is the kidney more efficient at clearing or conserving water?

More efficient at clearing water

10

What contributes 40% of osmolarity in the medullary ISF?

Urea

11

What features contribute to the preservation of medullary interstitial hyperosmolarity?

Low medullary blood flow (1-2% of renal flow)
Countercurrent exchanges via vasa recta

12

What causes a deficiency in the kidney's ability to concentrate or dilute urine?

Defecting in AVP secretion
Defect in response to AVP (at CD)
Defect in medullary osmolarity gradient

13

What are the types of diabetes insipidus?

Central
Nephrogenic

14

What is the mechanism of central diabetes insipidus?

Pituitary gland fails to release AVP

15

What is the mechanism of nephrogenic diabetes insipidus?

No response to AVP at CD
V2 receptor mutation
AqP-2 mutation
Drugs (lithium, tetracycline)

16

What causes loss of medullary hyperosmolarity?

Diuretics
Excessive delivery to LOH
Decreased urea production
Renal failure