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Renal Physio > Tubular Transport II > Flashcards

Flashcards in Tubular Transport II Deck (38):
1

Water loss from body

sweat, respiration, feces, urine, vomit

2

Water gain to body

oral

3

The amount of water that leaves the body affects the

plasma osmolality

4

ECF Volume is a reflection of the

Body Na content

5

ECF volume is sensed by

arterial and cardiac baroreceptors

6

Low/High ECF volume triggers

Ang II, aldosterone, SNS/ANP

7

Low/High ECF volume leads to the

excretion or retention of Na

8

Plasma osmolality is a reflection of the

body water content of body fluid

9

HIgh/Low Plasma osmolality is sensed by

hypothalamic osmoreceptors

10

High/Low Plasma osmolality leads to the

excretion of H2O or intake of H2O (thirst)

11

A problem with total body water manifests as

plasma osmolality alteration [Na]

12

problems with total body Na content manifest as

ECF volume alteration

13

Diuresis

excretion of large amounts of urine (hypoosmolar)

14

Antidiuresis

excretion of small amount of urine (hyperosmolar)

15

Normal plasma osmolality is

275-295

16

ADH release is triggered by

atrial or arterial baroreceptors

17

ADH is released from the __________ due to signals from __________

posterior pituitary; hypothalamic osmoreceptors

18

Osmoreceptors in the hypothalamus sense change sin

plasma osmolality

19

Low plasma osmolality -->

reduced ADH --> decreased reabsorption of H2O in the collecting duct

20

When plasma osmolality is <280 , ADH is

almost 0!

21

High plasma osmolality -->

increased ADH --> increased reabsorption of water (AQP-2)

22

ADH mechanism

binds to vasopressin-2 (V2) receptor on principal cells --> increased cAMP --> increased AQP-2 --> H2O reabsorption

23

What 2 things are necessary to concentrate urine?

ADH and permeable distal tubule and collecting duct AND hypertonic medullary gradient

24

What establishes the hypertonic medullary gradient?

thick ascending limb reabsorption of solutes (NaCl and urea)

25

Countercurrent multiplication

arrangement of loop of Henle and the collecting duct, creates a gradient as the loop dips deeper into the medulla

26

Dilution of urine requires 2 things

reabsorption of solutes (W/O H2O) in the thick ascending limb AND low levels of ADH

27

Concentration of urine step-wise

isoosmolar (300) filtrate in descending limb loses H2O to become hyperosmolar (600), NaCl is lost in the thin ascending limb and Na-K-Cl reabsorbs solute in the thick ascending limb to create a hypoosmolar filtrate (150), NaCl is reabsorbed in the distal tubule and collecting duct (W/O H2O loss) concentrating the urine to 50mOsm

28

Concentrating the urine step-wise

isoosmolar (300) filtrate in descending limb loses H2O to become hyperosmolar (600), NaCl is lost in the thin ascending limb and Na-K-Cl reabsorbs solute in the thick ascending limb to create a hypoosmolar filtrate (150), in the presence of ADH H2O can rapidly move down it's concentration gradient in the distal tubule and collecting duct until it equilibrates with its surrounding (1200mOsm)

29

What happens if the NaCl reabsorption out of the thick limb is impaired?

hypertonic gradient cannot be established and concentrating the urine cannot take place

30

Role of Urea in medulla osmolality

In conditions of severe dehydration, ADH phosphorylates urea transporters (UT-A1) in the thick ascending limb and allows for the resorption of Urea. Contributing to the maximal ability to concentrate the urine.

31

How would a high protein diet effect the ability to concentrate urine?

High protein, high urea in filtrate, higher medullary interstitial, greater ability to concentrate urine.

32

How would consuming large amounts of water contribute to the ability to concentrate urine?

Large amounts of water, large amounts of flow in vase recta, "washing-out" of solutes in hypertonic medulla --> decreased ability to concentrate urine

33

Why isn't the maximum medullary osmolarity 1200 during diuresis?

Low ADH --> less urea in interstitial, and large volume flow through the vasa recta "washes-out" hypertonic medulla

34

If vasa recta blood flow is decreased, what will happen to the concentrating ability of the kidney?

decreased blood flow, decreased ATP and O2 for Na reabsorption, decreased osmolality of interstium, DECREASED ability to concentrate urine

35

Comparison of urine osmolality to plasma osmolality tells you if you are concentrating or diluting the urine

hypoosmolar: Uosm < Posm (dilute urine)
isoosmolar: Uosm = Posm
Hyperosmolar: Uosm > Posm (concentrating urine)

36

Free water clearance

(+) Ch2o added to urine to make it dilute
(-) Ch2o retained to make urine concentrated

37

Negative water clearance is called

TcH2O (tubular conservation of H2O)

38

Positive water clearance is called

CH2O