Loop of Henle, DT and CD

Question 1

Functions of the Loop of Henle

Answer 1

1. Reabsorbs 25% of filtered Na+ without H2O- first part of making the urine a different osmolality than plasma

Question 2

T/F Descending limb is only permeable to H2O

Answer 2

T

Question 3

Na+, K+, 2Cl- carrier functions

Answer 3

1. reabsorbs about 20% of the filtered load of Na+

2. ALL sites must be occupied to function- lack of Cl- is the rate limiting step

Question 4

Barrter syndrome

Answer 4

Genetic mutations in any of the transporters in the thick ascending limb= NO Na+/K+/2Cl- would be reabsorbed

Question 5

Lasix

Answer 5

Blocks the Na+/K+/2Cl- carrier

Question 6

T/F There are aquaporins in the thick ascending limb

Answer 6

F- only solutes are reabsorbed

Question 7

Functions of the Distal tubule

Answer 7

1. reabsorbs about 5% of the filtered Na+ via a Na+/Cl- transporter
2. Dilutes the urine= decreases osmolality

Question 8

T/F There are no aquaporins in the distal tubule

Answer 8

T- they only reabsorb Na+

Question 9

Gitleman Syndrome

Answer 9

genetic mutation of the Na/Cl transporter in the DT

Question 10

HCTZ

Answer 10

Manipulates the DT Na/Cl transporter

Question 11

Functions of Collecting duct

Answer 11

1. Variable Na+ reabsorption- anywhere from 0-5%
   - 1st area that is directly controlled to determine the urinary electrolyte concentration
2. Variable permeability to H2O

Question 12

Two types of cells in the CD

Answer 12

1. principal cells

2. intercalated cells

Question 13

Principal Cells

Answer 13

In CD

1. Contributes to salt, Cl- and K+ reabsorption/excretion
   - from 0-4.9%

Question 14

What hormone is the primary mechanism of controlling salt reabsorption and K+ secretion via the principal cells?

Answer 14

Aldosterone

Question 15

What regulates Aldosterone?

Answer 15

Renin, Angiotensin I and Angiotensin II

Question 16

What 3 pathways can stimulate renin?

Answer 16

1. NE via SNS
2. Decreased stretch in afferents
3. Decreased Cl- delivery to the macula densa
   - these stimulate release of renin from JG cells

Question 17

Primary actions of Angiotensin II (4)

Answer 17

1. stimulates aldosterone
2. systemic vasoconstrictor
3. stimulates PT reabsorption of Na+
4. Increases SNS activity

Question 18

Functions of Aldosterone

Answer 18

It is lipophilic so it crosses the membrane freely and binds to the SRE’s
1. increases transcription, translation and insertion of the Na+/K+ pump, ENac and ROMK
= increases the activity and/or number of these

Question 19

Liddle’s Syndrome

Answer 19

Increase in function of ENaC channels- no control of these channels; Absorb Na+

Question 20

Type 1 pseudohyperaldosteronism

Answer 20

1. ENaC has loss of function= it can’t work= SALT WASTING

Question 21

Equation for determining the amount of solute that is delivered to the kidney-

Answer 21

(Solute concentration) x (RPF)

* don’t forget about units*

Question 22

Factional excretion of Na+ (FENa)=

Answer 22

Used to determine if there is a prerenal problem or not- normal ~ 1%
(excreted/filtered) x 100

Question 23

Na+ excretion rate equation

Answer 23

(Urine Na+)x(total urine output)

Question 24

Clearance of solute equation

Answer 24

excretion rate/ plasma concentration of solute

Question 25

Na+ reabsorptive rate equation

Answer 25

(filtered load) - (excretion rate)

Question 26

Filtered solute load equation

Answer 26

GFR x [plasma solute]

Question 27

Total solute delivered to kidney equation

Answer 27

Solute plasma concentration x RPF