Sodium and water transport along the nephron Flashcards Preview

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Flashcards in Sodium and water transport along the nephron Deck (54):
1

How many moles of sodium are filtered in the Bowman's capsule a day?

2500 mmoles

2

How many moles of sodium are excreted a day?

150 mmol

3

How many litres of blood are filtered a day?

180 L

4

How many litres of urine are produced a day?

1.5 L

5

What happens to the sodium and water that are not excreted?

Reabsorbed in the tubules

6

What are the sites of reabsorption in the tubule?

PCT -> PST -> DTLLH -> TALLH -> DCT -> Collecting duct

7

What reabsorption happens in the PCT?

50% water and 50% sodium is reabsorbed Isotonic

8

What reabsorption happens in the PST?

20% water and 20% sodium Isotonic

9

What reabsorption happens in the DTLLH?

5% water

10

What reabsorption happens in the ATLLH?

20% sodium

11

What reabsorption happens in the DCT?

5% sodium

12

What reabsorption happens in the collecting duct?

4% sodium 19% water

13

In which parts of the tubule is reabsorption isotonic?

PCT and PST

14

Which parts of the tubule are impermeable to water?

TALLH and DCT

15

What separates the lumen and interstitial fluid in a renal epithelial cell?

Tight junction

16

What controls most reabsorption in the renal epithelial cells?

Sodium movement

17

What controls movement of sodium in and out of renal epithelial cells?

Sodium potassium pump

18

What does the lumen refer to?

The tubule

19

What does the interstitial milieu refer to?

The blood

20

What substances are reabsorbed in the PCT along with sodium?

Glucose Amino acids Phosphate Chlorine Protons Water

21

What type of transporters control the movement of these molecules along with sodium?

Most are symporters Protons - sodium - proton antiporter Chlorine - channel Water - aquaporins

22

What feature makes cells permeable to water?

Presence of aquaporins

23

What is the role of the TDLLH in controlling salt and water reabsorption?

Mainly control equilibration of sodium and water via channels and aquaporins

24

Is the process of reabsorption in the TALLH active?

Yes - requires lots of ATP

25

What type of cotransporter is uniquely present on epithelial cells of the TALLH?

2-chloride, potassium, sodium cotransporter

26

What does the potassium transporter on TALLH epithelial cells do?

Recycle potassium

27

Why is a positive transepithelial potential created in TALLH epithelial cells?

Chlorine is transported into the blood - 2 chlorines for every sodium Transporting more chlorine ions than sodium = positive transepithelial potential

28

What does this positive transepithelial potential do?

Transports additional chlorine, sodium, potassium and calcium through a paracellular shunt

29

Which cells of the collecting duct regulate water and sodium reabsorption?

ENaC - epithelial sodium channel ROMK - Renal Outer Medullary Potassium Channel

30

Is water and sodium permeability regulated in collecting duct epithelial cells?

Yes

31

What is the name of the cells in the colllecting duct that regulate sodium and water reabsorption?

Principal cells

32

How do ENaC and ROMK work to control sodium and potassium concentration?

Sodium reabsorption is paralleled by potassium excretion into the urine

33

How does the ability to regulate the expression of ROMK and ENaC affect the function of the collecting ducts?

Allows Potassium excretion to be regulated by the cells Sodium concentration in the urine to be regulated

34

What is Tmax?

Point at which increases in concentration of a molecule does not result in an increase in the movement of a substance across a membrane

35

What is the Tmax of glucose?

10 mmol/L

36

What happens if there is glucose in urine?

Osmotic diuresis Dehydration

37

What is glycosuria?

Glucose in the urine

38

What are two conditions that can lead to glycosuria?

Renal glycosuria - defective uptake in PCT due to mutation in SGLT2 (gene encoding for sodium glucose cotransporter) Diabetes mellitus - plasma glucose is very high, exceeds transport capacity of nephrons

39

What are names of diseases affecting salt handling?

Bartter's syndrome EAST syndrome Pseudohypoaldosteronism Gitelman's syndrome Liddle syndrome

40

What is Barterr's syndrome?

Condition that affects the 2 major ion transporters of TALLH NKCC2 ROMK - recycling potassium pathway ClC-K

41

What is EAST syndrome?

Affects basolateral potassium channels in the DCT

42

What is Gitelman's syndrome?

Affects NaCl cotransporters in the DCT

43

What is Pseudohypoaldosteronism?

Gain of function of ENaC in the collecting duct

44

What is Liddle syndrome?

Loss of function of ENaC in the collecting duct

45

What are diseases affecting water handling?

Nephrogenic

Central

Nephrogenic syndrome of innapropriate antidiuresis

Diabetes insipidus

46

What is the reason for central source affecting water handling?

Low secretion of ADH from pituitary

Due to pituitary tumours or due to post surgery effects

47

How does diabetes insipidus affect water handling?

Large amounts of severly diluted urine is produced

Due to impaired glucose metabolism

48

How does nephrogenic syndrome of innapropriate antidiuresis affect water handling?

Gain of function of V2 ADH receptors

49

How does nephrogenic syndrome affect water handling?

Collecting ducts do not respond to ADH

50

What does a generalised renal epithelial cell look like?

51

What does a PCT epithelial cell look like? 

52

What does a TALLH epithelial cell look like?

53

What does a DCT epithelial cell look like?

54

What does a principal cell look like?