phys

Question 1

which 2 parts of the nephron use counter-current multiplication to concentrate the urine and regulate urine concentration?

Answer 1

• loop of henle

- collecting duct

Question 2

why do only mammals and birds have the ability to concentrate their urine?

Answer 2

they are the only species with a loop of henle

Question 3

what are juxtamedullary nephrons and what % of nephrons do they make up?

Answer 3

nephrons going deep into the medulla

15%

Question 4

what are the symptoms of Bartter’s syndrome?

Answer 4

• salt wasting = struggle to reabsorb Na+ and Cl-
• polyuria
• hypokalaemia
• metabolic alkalosis
• hypercalciuria
• nephrocalcinosis

Question 5

what does the membrane of the thick ascending limb cell consist of?

Answer 5

apical (lumen)
- NKCC2 
- ROMK
basolateral (interstitial fluid)
- Na+/K+ ATPase 
- K+ channel
- CLCK 
- Barttin (regulates CLCK)

Question 6

UT-A1

Answer 6

urea transporter on apical membrane of inner medullary collecting duct

Question 7

what will happen to a UT-A1/A3 KO mouse when you restrict H2O availability?

Answer 7

• no urea transporters so no urea in interstitial fluid
• no driving force for H2O reabsorption
• cannot retain H2O
  disrupted counter current multiplication

Question 8

UT-B

Answer 8

urea transporter on RBCs

Question 9

osmolality equation

Answer 9

[X] * n

units = mOsmol/kgH2O

Question 10

UT-A3

Answer 10

urea transporter on basolateral membrane of inner medullary collecting duct