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Kidneys and Hormones > Sodium and water transport along the nephron > Flashcards

Sodium and water transport along the nephron Flashcards

1
Q

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

A

2500 mmoles

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2
Q

How many moles of sodium are excreted a day?

A

150 mmol

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3
Q

How many litres of blood are filtered a day?

A

180 L

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4
Q

How many litres of urine are produced a day?

A

1.5 L

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5
Q

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

A

Reabsorbed in the tubules

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6
Q

What are the sites of reabsorption in the tubule?

A

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

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7
Q

What reabsorption happens in the PCT?

A

50% water and 50% sodium is reabsorbed Isotonic

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8
Q

What reabsorption happens in the PST?

A

20% water and 20% sodium Isotonic

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9
Q

What reabsorption happens in the DTLLH?

A

5% water

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10
Q

What reabsorption happens in the ATLLH?

A

20% sodium

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11
Q

What reabsorption happens in the DCT?

A

5% sodium

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12
Q

What reabsorption happens in the collecting duct?

A

4% sodium 19% water

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13
Q

In which parts of the tubule is reabsorption isotonic?

A

PCT and PST

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14
Q

Which parts of the tubule are impermeable to water?

A

TALLH and DCT

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15
Q

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

A

Tight junction

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16
Q

What controls most reabsorption in the renal epithelial cells?

A

Sodium movement

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17
Q

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

A

Sodium potassium pump

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18
Q

What does the lumen refer to?

A

The tubule

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19
Q

What does the interstitial milieu refer to?

A

The blood

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20
Q

What substances are reabsorbed in the PCT along with sodium?

A

Glucose Amino acids Phosphate Chlorine Protons Water

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21
Q

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

A

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

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22
Q

What feature makes cells permeable to water?

A

Presence of aquaporins

23
Q

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

A

Mainly control equilibration of sodium and water via channels and aquaporins

24
Q

Is the process of reabsorption in the TALLH active?

A

Yes - requires lots of ATP

25
Q

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

A

2-chloride, potassium, sodium cotransporter

26
Q

What does the potassium transporter on TALLH epithelial cells do?

A

Recycle potassium

27
Q

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

A

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

28
Q

What does this positive transepithelial potential do?

A

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

29
Q

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

A

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

30
Q

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

A

Yes

31
Q

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

A

Principal cells

32
Q

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

A

Sodium reabsorption is paralleled by potassium excretion into the urine

33
Q

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

A

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

34
Q

What is Tmax?

A

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
Q

What is the Tmax of glucose?

A

10 mmol/L

36
Q

What happens if there is glucose in urine?

A

Osmotic diuresis Dehydration

37
Q

What is glycosuria?

A

Glucose in the urine

38
Q

What are two conditions that can lead to glycosuria?

A

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
Q

What are names of diseases affecting salt handling?

A

Bartter’s syndrome EAST syndrome Pseudohypoaldosteronism Gitelman’s syndrome Liddle syndrome

40
Q

What is Barterr’s syndrome?

A

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

41
Q

What is EAST syndrome?

A

Affects basolateral potassium channels in the DCT

42
Q

What is Gitelman’s syndrome?

A

Affects NaCl cotransporters in the DCT

43
Q

What is Pseudohypoaldosteronism?

A

Gain of function of ENaC in the collecting duct

44
Q

What is Liddle syndrome?

A

Loss of function of ENaC in the collecting duct

45
Q

What are diseases affecting water handling?

A

Nephrogenic

Central

Nephrogenic syndrome of innapropriate antidiuresis

Diabetes insipidus

46
Q

What is the reason for central source affecting water handling?

A

Low secretion of ADH from pituitary

Due to pituitary tumours or due to post surgery effects

47
Q

How does diabetes insipidus affect water handling?

A

Large amounts of severly diluted urine is produced

Due to impaired glucose metabolism

48
Q

How does nephrogenic syndrome of innapropriate antidiuresis affect water handling?

A

Gain of function of V2 ADH receptors

49
Q

How does nephrogenic syndrome affect water handling?

A

Collecting ducts do not respond to ADH

50
Q

What does a generalised renal epithelial cell look like?

A
51
Q

What does a PCT epithelial cell look like?

A
52
Q

What does a TALLH epithelial cell look like?

A
53
Q

What does a DCT epithelial cell look like?

A
54
Q

What does a principal cell look like?

A

Kidneys and Hormones (39 decks)

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