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BRS Y2 > Renal Regulation of Water and Acid/base Balance > Flashcards

Renal Regulation of Water and Acid/base Balance Flashcards

1
Q

How is osmolarity calculated?

A

Concentration x No. of dissociated particles

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2
Q

When calculating osmolarity what would be the no of dissociated particles for NaCl vs for glucose

A 
NaCl= 2
Glucose= 1
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3
Q

What are the units for osmolarity?

A

mOsm/L

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4
Q

Are osmolarity and concentration the same? Explain why

A

No because the no of dissociated particles may be greater than one, this causes osmolarity to be greater than concantration

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5
Q

What % of body weight is total fluid volume?

A

60%

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6
Q

What proportion of total body fluid is extracellular vs intracellular?

A 
Extracellular= 1/3
Intracellular= 2/3
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7
Q

What does unregulated water loss encompass?

A

Sweat
Faeces
Vomit
Water evaporation from respiratory lining and skin

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8
Q

Describe ECF vol, [Na+] and osmolarity when there is a positive water balance

A

ECF vol=high
[Na+]=low
Osmolarity=low

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9
Q

Describe ECF vol, [Na+] and osmolarity when there is a negative water balance

A

ECF vol=low
[Na+]=high
Osmolarity=high

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10
Q

What happens to urine production when theres a positive water balance?

A

Hypoosmotic urine production

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11
Q

What happens to urine production when theres a negative water balance?

A

Hyperosmotic urine production

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12
Q

What does the medullary interstitium need to be for passive water reabsorption?

A

Hyperosmotic

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13
Q

How much water does the PCT reabsorb?

A

67%

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14
Q

What is reabsorbed in the descending limb of the loop of Henle and how?

A

Water (passively)

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15
Q

What is reabsorbed in the thin ascending limb of the loop of Henle and how?

A

NaCl (passively)

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16
Q

What is reabsorbed in the thick ascending limb of the loop of Henle and how?

A

NaCl (actively)

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17
Q

Describe how the counter current multiplication is set up?

A

New filtrate arrives in the loop of Henle
When it reaches the thick ascending limb sodium is actively pumped out (osmolarity in the medulla increases)
Another set of new filtrate arrives and water now passively moves out because the medulla has a greater osmolarity (the osmolarity of the fluid increases)
This hyperosmolar fluid moves down the descending limb so the osmolarity at the bottom is greater than at the top
This process continues and the gradient is set up with osmolarity higher at the bottom of the loop and lower at the top

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18
Q

Where is the UT A1 transporter found?

A

Apical membrane of the collecting duct

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19
Q

Where is the UT A3 transporter found?

A

Basolateral membrane of the collecting duct

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20
Q

Where is the UT A2 transporter found?

A

Thin descending limb of the loop of Henle

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21
Q

Where is the UT B1 transporter found?

A

Vasa recta

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22
Q

What is the purpose of urea recycling? (ie why is it useful)

A

It increases the osmolarity of the medulla to allow passive water reabsorption more easily and means urine excretion requires less water

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23
Q

Describe how urea recycling occurs

A

Urea is pumped into the filtrate via UT a2 transporter in the tin descending limb of the loop of Henle
Urea is pumped out into the medulla in the collecting duct via UT a3 and a1 transporters, increasing medulla osmolarity and encouraging passive water reabsorption
Urea is reabsorbed into the vasa recta via UT b1 transporter so it can be recylced and pumped into filtrate by UT a2 again

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24
Q

What is the role of vasopressin in urea recycling?

A

It boosts numbers of UT a1 and a3

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25
Q

What hormone boosts numbers of UT a1 and a3 ?

A

Vasopressin

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26
Q

What is the main function of vasopressin?

A

Promote water reabsorption from collecting duct

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27
Q

Where is vasopressin produced?

A

Hypothalamus (neurons in supraoptic & paraventricular nuclei)

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28
Q

Where is vasopressin stored?

A

Posterior pituitary

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29
Q

What factors that stimulate ADH production and release?

A 
Increased plasma osmolarity
Hypovolemia/low BP
Nausea
Angiotensin II
Nicotine
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30
Q

What factors that inhibit ADH production and release?

A

Reduced plasma osmolarity
Hypervolemia/high BP
Ethanol
Atrial natriuretic peptide

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31
Q

What detects fluctuations in plasma osmolarity?

A

Osmoreceptors

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32
Q

Out of osmo and baroreceptors which is more sensitive?

A

Osmoreceptors

33
Q

How does ADH work?

A

It binds to the V2 receptor on the basolateral membrane of principal cells
This causes a G protein cascade
The cascade results in activation of protein kinase A
This causes the no of aquaporin 2 channels to increase
They insert into the apical membrane of principal cells
This allows increased water reabsorbtion

34
Q

What is the name of the receptor for ADH and where is it found?

A

V2 receptor, found on the basolateral membrane of principal cells in the kidney

35
Q

What results in an increased no of aquaporin 2 channels?

A

Protein kinase A

36
Q

Where do aquaporin 2 channels insert?

A

Apical membrane of principal cells

37
Q

How is NaCl reabsorbed in the thick ascending limb?

A

Na+, K+ and 2 x Cl- move into the cell via symporter
3 Na+ are reabsorbed into blood while 2 K+ are pumped back into the cell by the Na+ K+ ATPase pump (this breaks one molecule of ATP into ADP+ Pi)
The K+ Cl- symporter then pumps one molecule of each into the blood from in the cell

38
Q

What is the medical term for increased dilute urine excretion?

A

Diuresis

39
Q

How is NaCl reabsorbed in the DCT?

A

One Na+ and one Cl- are moved into the cell via symporter
3 Na+ are reabsorbed into blood while 2 K+ are pumped back into the cell by the Na+ K+ ATPase pump (this breaks one molecule of ATP into ADP+ Pi)
The K+ Cl- symporter then pumps one molecule of each into the blood from in the cell

40
Q

How is Na+ reabsorbed in the principal cells of the collecting duct?

A

Na+ moves into the cell passively
3 Na+ are reabsorbed into blood while 2 K+ are pumped back into the cell by the Na+ K+ ATPase pump (this breaks one molecule of ATP into ADP+ Pi)

41
Q

What is the medical term for concentrated urine in low volume excretion?

A

Anti-diuresis

42
Q

What transporter is involved in Na+ reabsorption in the thick ascending limb?

A

Na+ - K+ - 2Cl- symporter

43
Q

What transporter is involved in Na+ reabsorption in the distal convoluted tubule?

A

Na+ - Cl- symporter

44
Q

What transporter is involved in Na+ reabsorption in the collecting duct?

A

Na+ channel

45
Q

What does ADH support the reabsorption of?

A

Na+

46
Q

What is ADH conc in anti diuresis?

A

High

47
Q

What is ADH conc in diuresis?

A

Low

48
Q

What is the cause of central diabetes insipidus?

A

Decreased or no production and release of ADH

49
Q

What are clinical features of central diabetes insipidus?

A

Polyuria

Polydipsia

50
Q

How is central diabetes insipidus treated?

A

External ADH

51
Q

What is the cause of syndrome of inappropriate ADH secretion (SIADH)?

A

Increased production and release of ADH

52
Q

What are clinical features of syndrome of inappropriate ADH secretion?

A

Hyperosmolar urine
Hypervolemia
Hyponatremia

53
Q

How is SIADH treated?

A

Non peptide inhibitor of ADH receptor

54
Q

What is the cause of nephrogenic diabetes insipidus?

A

Less or mutant aquaporin A2/V2 receptor

55
Q

What are clinical features of nephrogenic diabetes insipidus?

A

Polyuria

Polydipsia

56
Q

How is nephrogenic diabetes insipidus treated?

A

Thiazide diuretics and NSAIDs

57
Q

How is the acid base balance affected by our diet?

A

Acids and bases are added to our fluid compartment via our diet

58
Q

Are acids or bases excreted in the faeces?

A

Bases are

59
Q

After acid and base intake, what is the net addition in our body?

A

Acid 950-1000 mEq/day

60
Q

How are acids neutralised?

A

Bases react with the and form salts

61
Q

What is the role of kidneys in the acid base balance?

A

Secretion and excretion of H+
Reabsorption of hco3-
Produce new hco3-

62
Q

What regulates the acid bases balance?

A

Kidneys and lungs

63
Q

When acids are neutralised what is formed?

A

Salt, water and co2

64
Q

What is the Henderson Hasselbalch equation used to calculate?

A

The pH of a buffer solution when you know the conc of acid and its conjugate base in the solution

65
Q

What type of acid base disorder is change in pco2 associated with?

A

Respiratory

66
Q

What type of acid base disorder is change in [hco3-] associated with?

A

Metabolic

67
Q

Where is most hco3- reabsorbed?

A

PCT (80%)

68
Q

What 2 types of cell in the DCT are associated with hco3-?

A

Alpha and beta intercalated cells

69
Q

What happens to hco3- and h+ in alpha intercalated cells?

A

hco3- is reabsorbed

h+ is secreted

70
Q

What happens to hco3- and h+ in beta intercalated cells?

A

hco3- is secreted

h+ is reabsorbed

71
Q

Out of alpha and beta intercalated cells which is usually more important?

A

Alpha

72
Q

How is hco3- produced in the PCT?

A

Glutamine is broken down into 2 ammonia molecules and 2 hco3-

73
Q

What is required alongside bicarbonate ion reabsorption to neutralise the acid?

A

New bicarbonate ion production

74
Q

In the nephron, what area has the highest osmolarity?

A

The tip of the loop of Henle as it is the first part of the nephron in the medulla and has the highest osmolarity threshold (1200 mOsm/L)

75
Q

Why would chronic cirrhosis lead to high urine osmolarity?

A

Chronic cirrhosis causes urine retention in the body, the blood vessels therefore dilate and baroreceptors sense low BP. They will therefore release ADH increasing water reabsorption and increasing urine osmolarity

76
Q

What compartment does water first go into when we drink it?

A

Extracellular

77
Q

Which component of urine has no effect on ADH production?

A

Urea

78
Q

What effect does ethanol have on ADH levels?

A

Inhibits ADH release

BRS Y2 (85 decks)

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