Renal Physiology: Urinary Concentration and Dilution

Question 1

Hyposmotic body fluids create a ________ urine

Answer 1

dilute, (50 mOsm/L)

Question 2

Hyperosmotic body fluids create a ______ urine

Answer 2

concentrated (1200 mOsm/L)

Question 3

Can the kidneys regulated water excretion independently of solute excretion?

Answer 3

yes

Question 4

The countercurrent multiplier ensures high concentration gradient from ________ to the _________

Answer 4

corticomedullary border (proximal descending loop)

to the (papilla)

Question 5

The osmotic gradient in the ISF from the cortex to the medulla is used to do what?

Answer 5

remove water from urine in the collecting duct

Question 6

This portion of the loop of henle has the following characteristics…

• no active transport of NaCl
• very water permeable

Answer 6

Descending limb

Question 7

This portion of the loop of henle has the following characteristics…

• Increases in thickness
• actively reabsorbs NaCl
• impermeable to water

Answer 7

ascending limb

Question 8

by what mechanism is NaCl pumped form the ascending limb?

Answer 8

active transport

Question 9

What is the largest possible gradient across the wall of the ascending limb?

Answer 9

200 mOsm

Question 10

What is the essential component to maintaining the countercurrent multiplier?

Answer 10

active transport of sodium and chloride ions

Question 11

What is meant by “countercurrent” in countercurrent multiplier

Answer 11

flow of current occurs in opposing direction through the two limbs

Question 12

What transporter present in the thick ascending limb of the LOH is responsible for active transport of ions from the ascending limb to the interstitium?

Answer 12

Na+, K+, 2Cl- transporter (NKCC2)

Question 13

what blocks the NKCC2 receptor, leading to duresis?

Answer 13

furosemide

Question 14

What stimulates NKCC2 leading to antiduresis?

Answer 14

ADH

Question 15

What ensures that the renal blood flow doesn’t wash away the concentrated solute in the medullary ISF?

Answer 15

Countercurrent exchange in the vasa recta

Question 16

Is the countercurrent exchange in the vasa recta active or passive?

Answer 16

passive

Question 17

As blood flows down a hairpin loop of vasa recta, what occurs? What about the ascending part of the hairpin?

Answer 17

NaCl into capillary

H20 diffused out of capillary

opposite for ascending

Question 18

the early distal convoluted tubule has what kind of transporter?

Answer 18

NaCl transporter NCC

Question 19

NCC transporter is blocked by what?

Answer 19

thiazide diuretics

Question 20

The early portion of the distal tubule is impermeable to what?

Answer 20

water

Question 21

What is the osmolarity of the early distal convoluted tubule?

Answer 21

50 mOsm

Question 22

The late distal tubule and collecting dict have what two cell types?

Answer 22

Principal cells

Alpha intercalated cells

Question 23

This cell type in the late distal tubule has the following characteristics…

Reabsorbes Na+
Secretes K+
Site of aldosterone action
Site of ADH action

Answer 23

principal cells

Question 24

This cell type in the late distal tubule has the following characteristics…

Secretes H+
Reabsorbes K+

Answer 24

Alpha intercalated cells

Question 25

What determines sodium reabsorption and potassium secretion?

Answer 25

Basolateral Na,K ATPase and apical ion channels

Question 26

What controls water and urea permeability in the collecting duct?

Answer 26

ADH

Question 27

High ADH increases the expression of what on the apical membrane, leading to what changes?

Answer 27

AQP2, increased water reabsorption, concentrated urine

Question 28

What percentage of sodium and water are reabsorbed in the proximal tubule, leaving tubular fluid ________?

Answer 28

60-80% reabsorbed

isosmotic fluid

Question 29

Where is water primarily reabsorbed, making fluid hyperosmotic?

Answer 29

descending limb of LOH

Question 30

Where does most NaCl reabsorption occur, making fluid hyposmotic?

Answer 30

ascending limb of LOH

Question 31

What is reabsorbed in the early distal tubule, leading to a hyposmotic fluid?

Answer 31

NaCl