Renal Physiology And Bp: Nephron

Question 1

Nephron structure consists of:

Answer 1

Bowman’s capsule
Glomerulus
PCT
Loop of Henley
DCT
Collecting duct

Question 2

NEPHRON STRUCTURE main steps:

Answer 2

1. Filtration
2. Reabsorption
3. Secretion

Question 3

Summary of nephron function

Answer 3

1. Filtration at the glomerular capillaries in the renal corpuscle
2. Active removal of ions, glucose and amino acids at the PCT
3. Water reabsorption in the PCT and descending lib of LOH increase filtrate conc.
4. Active transport of Na+ and Cl- from ascending limb
5. Reabsorption and secretion in the DCT
6. Final reabsorption of water In collecting duct

Question 4

Mech. For reabsorbing ions

Answer 4

Combination of diffusion, osmosis and carrier mediated transport
Solutes such as glucose and ions are reabsorbed, water follows by osmosis

Question 5

Renal tubule made up of polarised epithelial cells = advantage of this?

Answer 5

Distinctly different membranes - APICAL and BASOLATERAL
Microvili increase the SA of absorption

Question 6

Apical vs basolateral membrane

Answer 6

Apical= in contact with tubular fluid
Basolateral= in close proximity to the peritubular capillaries

Question 7

Largest site of water reabsorption happens?

Answer 7

In PCT
60-70% by osmosis

Question 8

Two main mechanism of Na reabsorption in the PCT are through?

Answer 8

Sodium-hydrogen exchanger (NHE) and through sodium glucose transporters (SGLT)

Question 9

SGLT

Answer 9

UPATKES sodium and glucose together in the cell
Other transporters on basolateral membrane which allow passage of them

Question 10

Gliflozins are?

Answer 10

SGLT2 inhibitors
Useful in treatment of diabetes as they prevent reabsorption of glucose from filtrate and so it is excreted in the urine= lowers blood glucose

Question 11

NHE

Answer 11

Sodium is reabsorbed in exchange for H ions

Question 12

Dapagliflozin mechanism

Answer 12

Competitive reversible inhibitor = blocks SGLT2 proteins
And is highly selective
=prevents uptake of glucose, so some Na+/glucose is trapped in the urine which means you aren’t reabsorbing as much water = wee it out

Question 13

Descending limb vs ascending limb

Answer 13

Descending limb is impermeable to solutes, but permeable to water
Ascending= permeable to solutes but impermeable to water

Question 14

Countercurrent multiplication is?

Answer 14

Positive feedback loop that exist in the LOP
(When filtrate becomes more concentrated providing a gradient for NA and Cl to be pumped out )

Question 15

Countercurrent multiplication EXPALINED

Answer 15

Na+ and Cl- are pumped out of the ascending limb- elevates the osmotic conc. around the descending limb
Provides osmotic gradient for water to leave descending limb
=increases conc. of solutes in the descending limb which then arrive in the ascending limb and accelerates the transport of Na+ and Cl-

Question 16

NKCC transporter

Answer 16

Na/K/2Cl

Question 17

NKCC transporter is the site of action for?

Answer 17

Loop diuretics

Question 18

What is happening in The ascending loop of Henle?

Answer 18

Na+ and Cl- are actively reabsorbed

Question 19

NKCC at the apical membrane

Answer 19

Moves one Na+ , one K+ and 2 Cl- ions out of the filtrate into the cell every time it pumps

Question 20

2 further carriers on basolateral membrane ( the peritubular side, close to the capillaries) role

Answer 20

K-Cl cotransporter that removes one of each ion with every pump and there is a Na-K exchange pump
Activity of these pumps = net loss of Na and Cl, but not K as the levels maintained by the Na/K exchanger

Question 21

Loop diuretics site of action

Answer 21

NKCC cotransporter along ascending limb of the LOH in nephrons of the kidneys

Question 22

NCC

Answer 22

Na/Cl transporter
Carries out one NA and one Cl- ion

Question 23

What transporter in DCT?

Answer 23

NCC

Question 24

Thiazide diuretics tend to be first one of treatment for?

Answer 24

Hypertension

Question 25

Site of action for thiazide diuretics

Answer 25

Primarily DCT
Inhibit the NCC co-transporter

Question 26

In DCT Na+ and Cl- actively reabsorbed by?

Answer 26

Activity of the NCC transporter

Question 27

NCC located?

Answer 27

So the apical (tubular side) moves one Na+ and Cl-ion out of the cell with each pump

Question 28

Na+ in the peritubular space. What happens?

Answer 28

Exchange for K at the basolateral membrane by the Na/K pump
Cl- leaves by Cl -channels on the basolateral membrane

Question 29

Epithelial Na+ channels on collecting duct reabsorb?

Answer 29

Na+
These channels are sensitive to aldosterone

Question 30

Function of aquaporins in collecting duct

Answer 30

Reabsorb water
Sensitive to Vasopressin (ADH)

Question 31

Reabsorption mechanism : in PCT

Answer 31

NHE - sodium hydrogen exchanger
SGLT- glucose and sodium

Question 32

Reabsorption mechanism : LOH

Answer 32

NKC- sodium, potassium and 2 Chloride

Question 33

Reabsorption mechanism : DCT

Answer 33

NCC- Sodium and 2 chloride

Question 34

Reabsorption mechanism : collecting duct

Answer 34

ENaC- sodium channel aquaporins - water channels