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Renal > 05.08 - Reg of Body Fluid Osmolarity (Rao) - PP + Handout, No reading > Flashcards

05.08 - Reg of Body Fluid Osmolarity (Rao) - PP + Handout, No reading Flashcards

1
Q

4 Causes of Loss of Medullary Hyperosmolarity

A

(1) Diuretics; (2) Excessive delivery of fluid into LOH; (3) Decreased urea production; (4) Age, renal failure

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2
Q

Ability of kidneys to dilute or concentrate urine depends on

A

Difference between osmolar clearance and clearance of water

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3
Q

Activation of V2 in CD results in

A

insertion of Aquaporins into luminal membrane

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4
Q

Actual fluid flow - Cosm =

A

Free water clearance

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5
Q

ADH receptor in Epithelial cells of CD

A

V2

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6
Q

ADH responds to both

A

Posm, ECFV

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7
Q

At what plasma osmolarity does AVP reach max

A

295 mOsm

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8
Q

At what plasma osmolarity is AVP detectable

A

270-285 mOsm

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9
Q

AVP increase requires what threshold of ECFV loss

A

10-15% decrease in ECFV

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10
Q

Cause of Osmotic Diuresis

A

Hyperosmotic Plasma

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11
Q

Central Diabetes Insipidus results from

A

Pituitary gland doesn’t release AVP

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12
Q

Common symptom of decreased ability to concentrate urine

A

Nocturia

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13
Q

Complications of Polydipsia

A

Hyponatremia, Coma, Death

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14
Q

Cwater =

A

UF x (1 - Uosm/Posm)

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15
Q

Dec PV after GI loss causes ___, but decreased plasma osmolarity causes ____

A

Inc AVP, Dec AVP

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16
Q

Difference between osmolar clearance and water clearance is

A

Free Water Clearance

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17
Q

How does ADH affect Posm, Uosm in Osmotic Diuresis

A

Remains: High, High

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18
Q

How does ADH affect Posm, Uosm in Primary Polydipsia

A

Low to Normal, Low to High

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19
Q

How does CD help with Medullary Hyperosmolarity

A

Active transport of Na into ISF

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20
Q

How does GI fluid loss lead to hyponatremia

A

(1) AVP release in response to volume; (2) Dilution of plasma; (3) Inc ECF volume; (4) Reduced osmolarity, Hyponatremia

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21
Q

How does heart failure cause hyponatremia

A

Loss of pressure stimulates hypovolemic hormone release

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22
Q

How does IMCD help with Medullary Hyperosmolarity

A

Passive diffusion of urea into ISF

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23
Q

How does liver failure cause hyponatremia

A

Loss of PV stimulates hypovolemic hormone release

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24
Q

How does Thick AL help with Medullary Hyperosmolarity

A

Active NaCl transport, Co-transport of K and Cl into ISF

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25
Q

How does Water Deprivation affect Posm, Uosm, and ADH in Nephrogenic DI

A

Increase, No change, Increase

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26
Q

How does WD affect Posm, Uosm, and ADH in Osmotic Diuresis

A

Inc, Inc, Inc

27
Q

How does WD affect Posm, Uosm, and ADH in Primary DI

A

Increase, Remain low, No change

28
Q

How does WD affect Posm, Uosm, and ADH in Primary Polydipsia

A

Normalize, Normalize, Increase

29
Q

If free water clearance is negative, it means

A

Urine is being concentrated and BW is retained

30
Q

If Uosm is greater than Posm

A

Negative Cwater -> Concetrated Urine -> Dec Posm

31
Q

If Uosm is less than Posm

A

Positive Cwater -> Dilute urine -> Inc Posm

32
Q

In condition of sever ECFV loss, it doesn’t matter what ___, ___ will rise

A

Doesn’t matter what serum osmolarity is, AVP levels will rise

33
Q

Manifestations of Hyponatremia

A

Lethargy, Hyporeflexia, Mental confusion

34
Q

Mutations that can cause Nephrogenic Diabetes Insipidus

A

V2 receptor, Aquaporin-2 –> CD doesn’t respond to AVP

35
Q

Na imbalance with GI fluid loss

A

Hyponatremia

36
Q

Normal Cosm

A

2 +- 0.5 mL/min

37
Q

Obligatory Urine volume

A

.5 L / day

38
Q

Osmolar Clearance =

A

(UF x Uosm) / Posm

39
Q

Osmolar clearance is elevated under condition of

A

Plasma Hyperosmolarity

40
Q

Osmolar clearance measures

A

kidney’s ability to concentration urine

41
Q

Calculated Plasma Osmolarity =

A

2 x Na + (glu/18) + (bun/2.8)

42
Q

Positive free water clearance indicates

A

Dilution of urine and concentration of plasma

43
Q

Resting Posm, Uosm, and ADH in Osmotic Diuresis

A

High, High, Normal

44
Q

Substantial dec in ECFV stimulates ADH release even

A

under condition of hypo-osmolar plasma

45
Q

T/F: ADH increases linearly with decreased ECFV

A

False, logarithmic - Very slow increase at first until threshold met

46
Q

Thick Ascending Limb is permeable to

A

Active NaCl transport, (K, Cl)

47
Q

Thin Ascending Limb is permeable to

A

Passive NaCl, some urea

48
Q

Thin Descending Limb is permeable to

A

H20, some urea

49
Q

To assess efficacy of kidney to concentrate or dilute urine, must first

A

quantitate the rate of excretion of solute (using Osmolar Clearance)

50
Q

Two other conditions besides GI Fluid Loss that lead to Hyponatremia with no change in ECFV

A

(1) Heart Failure - Loss of pressure stimulates hypovolemic hormones; (2) Liver failure - Reduce PV stimulates hypovolemic hormones

51
Q

Two special features that contribute to preservation of medullary interstitial hyperosmolarity

A

(1) Meduallry BF is low; (2) Vasa recta serves as countercurrent exchanges

52
Q

Tx of Hyponatremia due to GI Fluid Loss

A

Infusion of Isotonic Saline, avoid quick change

53
Q

Under condition of severe volume loss, effect of ___ on ___ overides ___

A

Effect of ECFV loss on AVP overrides osmolarity effect

54
Q

Urea contributes what % of osmolarity in Medullary ISF

55
Q

Water clearance is how much

A

water without any solute is cleared in urine

56
Q

Water deprivation in DI must be stopped if

A

BW falls >5%, Posm > 300 mOsml/kg

57
Q

What can override normal response to plasma osmolarity

A

Severe decrease in ECFV

58
Q

What is dilemma with severe volume loss and low serum osmolarity

A

Low osmolarity inhibits ADH so as to correct; But severe volume loss overrides in order to maintain volume

59
Q

What signals mediate V2 activity

A

AC -> cAMP -> PKA

60
Q

Where are osmoreceptors in the brain that stimulate ADH release in response to increase osmolarity

A

Supraoptic and Paraventricular Nuclei of Hypothalamus

61
Q

Where is AVP degraded

A

PT and Liver

62
Q

Where is the thirst center in the brain?

A

Lateral Preoptic Nucleus of the Hypothalamus

63
Q

Which is more efficient: Clearing water or conserving

A

Clearing fo sho

64
Q

Which part of CD is permeable to Urea

A

Inner Medullary

Renal (31 decks)

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