Concentration/Dilution (lec 12)

Question 1

Normal urine is what-tonic?

Its normal osmolarity is?

Answer 1

hypertonic

285-295

Question 2

Kidney response to HYPOsmotic body fluid?

Answer 2

excretes dilute urine (water diuresis)

hyposmotic = water excess

Question 3

Kidney response to HYPERosmotic fluid?

Answer 3

excretes concentrated urine (antidiuresis)

hyperosmotic = water deficit

Question 4

Kidney’s ability to regulate water excretion is dependent or independent of solute excretion?

Answer 4

independent

Question 5

NaCl transport in descending LOH?

Answer 5

no active transport,

highly permeable to H2O

Question 6

NaCl transport in ascending LOH?

Answer 6

active transport of NaCl back to blood (reab),

impermeable to water

Question 7

Osmotic gradient in interstitial space (cortex to medulla) has what relationship with urine in collecting ducts?

Answer 7

it removes H2O from urine

Question 8

As fluid flows down descending LOH, what happens to the concentration?

Answer 8

becomes more [ ]

water is pulled from fluid

Question 9

As fluid flows up descending LOH, what happens to the concentration?

Answer 9

becomes diluted

NaCl is pulled from fluid

Question 10

Largest osmotic gradient possible across ascending LOH?

Answer 10

200

Question 11

Back diffusion = ?

Answer 11

active ion transport out of lumen

Question 12

Countercurrent Multiplier does?

Answer 12

creates large overall gradient from LOH (corticomedulla border to tip of papilla)

Question 13

Beginning osmolarity of fluid as enters Descending LOH?

Answer 13

300

Question 14

Countercurrent Multiplier: Thick Ascending Limb of LOH

NaCl transport mechanism?

Answer 14

Na+/K+/2Cl− cotransporter pulls NaCl from lumen into tubule cell

K+/Cl- cotrans and Na+/K+ pump move NaCl into medulla ISF

Ascending limb IMPERMEABLE to H2O, H2O can’t follow Na+

Question 15

Countercurrent Multiplier: Thick Ascending Limb of LOH

NaCl transport results in?

Answer 15

ISF osmolarity ↑ to 400,

ascending limb osmolarity ↓ to 200

Question 16

Countercurrent Multiplier: Descending Limb of LOH

H2O transport mechanism?

Answer 16

Fluid entering descending limb has 300 Osm,

ISF is now 400 Osm (from ascending transport of NaCl),

H2O pulled from lumen into ISF

Question 17

Coutercurrent Multiplier: Descending Limb of LOH

H2O transport results in?

Answer 17

descending limb osmolarity ↑ and is pushed down the limb,

fluid Osm keeps ↑ as it approaches distal turn of tube

Question 18

Main drive of the countercurrent multiplier is?

Answer 18

active transport

Question 19

Vasa Recta is?

Answer 19

capillary that follows inside the LOH hairpin turn

Question 20

Vasa Recta purpose?

Answer 20

preserve the ISF gradient created by LOH

Question 21

Vasa Recta: Descending Loop mechanism?

Answer 21

passive diffusion of NaCl in and H2O out

Question 22

Vasa Recta: Ascending Loop mechanism?

Answer 22

passive diffusion of H2O out and NaCl in

Question 23

Urea is made by?

Answer 23

hepatic protein catabolism

Question 24

Urea is recycled where in the kidney?

Answer 24

medulla

Question 25

Urea recycling is ↑ by?

Answer 25

ADH

Question 26

AHD affects Urea permeability how/where?

Answer 26

↑ urea permeability in the INNER medullary collecting ducts

Question 27

Early DCT: NaCl transportation mechanism?

Answer 27

NaCl cotransport and Na+ channel from lumen into cell Na+/K+ pump and Cl- channel move NaCl into ISF

Question 28

Early DCT: NaCl cotransport blocked by what?

Answer 28

thiazide diuretics

Question 29

Early DCT: Impermeable to what? Results in?

Answer 29

H2O continued dilution of tubular fluid, fluid remains HYPOsmotic

Question 30

Late DCT: Na+ and K+ transport mechanisms Basolateral membrane?

Answer 30

Na+/K+ATPase -> Na+ reabsorption/K+ secretion

Question 31

Late DCT: Na+ and K+ transport mechanisms Apical membrane?

Answer 31

Na+ and K+ channels

Question 32

Late DCT: Principle cells purpose? Controlled by?

Answer 32

reab Na+/secrete K+ Aldosterone

Question 33

Late DCT: Aldosterone affects Principle Cells how?

Answer 33

↑ # of apical Na+ channels, | ↑ Na+/K+ATPase

Question 34

Late DCT: ⍺-Intercalated cells purpose? Mechanism?

Answer 34

secrete H+/reab K+ (balance pH) H+ATPase H+/K+ATPase

Question 35

Collecting Duct (CD): Permeable to? ONLY in presence of?

Answer 35

H2O, Urea ADH (vasopressin)

Question 36

Collecting Duct: ADH mechanism to cause H2O permeability?

Answer 36

ADH binds baso memb of DCT or CD cells -> activates cAMP -> ↑ aquaporins (water channels) in apical membrane