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Urology and renal medicine > Renal regulation of water and acid-base balance > Flashcards

Renal regulation of water and acid-base balance Flashcards

1
Q

Describe the body’s fluid distribution in different compartments

A
  • 2/3 Intracellular fluid
  • 1/3 extracellular fluid (ECF)
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2
Q

Describe the different components of the extracellular fluid in order of abundance.

A
  • Interstitial fluid (that surrounds and bathes cells) 70ish percent
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3
Q

What happens at the PCT in the kidney water wise?

A

2/3 of water gets reabsorbed

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4
Q

What happens at the descending loop of Henle water and ion wise?

A
  • Water passively reabsorbed
  • NaCl isn’t reabsorbed
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5
Q

What happens in the ascending loop of Henle?

A
  • NaCl is reabsorbed passively in the thin ascending limb
  • NaCl is also reabsorbed actively in the thick ascending limb
  • Water can’t be reabsorbed
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6
Q

How does ADH work to regulate water reabsorption and where does it act?

A

ADH modulates aquaporin channels (open and closing them) to vary amount of water reabsorption, act on the DCT and collecting duct.

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7
Q

What happens at the DCT and collecting duct?

A

There’s a variable amount of water reabsorbed depending on body’s needs.
Action of ADH kicks in here.

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8
Q

How does the body passively reabsorb water into the body without spending a lot of energy. (2 words)

A

Countercurrent multiplication

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9
Q

In collecting duct cells what side does the basolateral cell membrane face?

A

The side with the blood capillaries

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10
Q

What side does the apical cell membrane face?

A

The lumen of the collecting duct (the inside of the tube)

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11
Q

What is the vasa recta?

A

A series of blood capillaries that surround nephron mainly in medullary region

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12
Q

How and where is urea transported out into the medullary interstitium?

A

Through UT-A1 and UT-A3 transporters in the inner collecting duct

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13
Q

Once the urea is in the interstitium what are its two paths?

A

-It can go into vasa recta through UT-B1 transporter which surrounds nephron

-It can go into descending limb of loop of Henle through UT-A2 transporter where it goes back through nephron and some exits collecting duct back into interstitium again

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14
Q

Which transporter is responsible for moving urea into the vasa recta?

A

UT-B1

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14
Q

Why is urea recycled?

A

To increase interstitium osmolarity which leads to helping conserve water.

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15
Q

When is vasopressin (ADH) released?

A

When plasma osmolality increases (dehydration)

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16
Q

What does vasopressin do to this mechanism?

A

Helps boost UT-A1 and UT-A3 numbers to increase collecting duct’s permeability for urea to aid urea reabsorption

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17
Q

What is Vasopressins main function?

A

Promote water reabsorption from collecting duct by increasing UREA and SODIUM reabsorbtion.

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18
Q

Where is ADH/ Vasopressin produced?

A

In hypothalamus by neurones in supraoptic and paraventricular nuclei

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19
Q

Where is ADH/Vasopressin then stored?

A

Once produced it’s packaged into granules and sent to posterior pituitary for storage

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20
Q

What does ADH do to the kidneys to conserve water?

A

leads to the insertion of aquaporin channels in collecting duct to reabsorb water.

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21
Q

What is hypovolemia?

A

Hypovolemia means low blood volume

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22
Q

Which receptors detect change in blood pressure?

A

baroreceptors

23
Q

What other factors stimulate ADH production and release? (3)

A
  • Nicotine
  • Nausea
  • Angiotensin II
24
Q

What is the target of ADH in the collecting duct?

A

V2 receptor on basolateral membrane of principal cells of collecting duct.

25
Q

What happens when ADH binds to V2 receptor?

A

It triggers a G-protein mediated signal cascade in the cell (protein kinase A involved) leads to the expression/ insertion of aquaporin channels.

26
Q

What is the next step in the ADH signal pathway after the G-protein mediated signal cascade is triggered?

A

Protein kinase A gets activated.

27
Q

What is the effect of protein kinase A activation in the ADH signal pathway?

A

It increases secretion of aquaporin 2 channels in vesicle form which are inserted into apical cell membrane.

28
Q

How does water get absorbed into the blood vessel in the collecting duct?

A

Water is absorbed through aquaporin 2 into the cell, and then through aquaporin 3 and 4 in the basolateral cell membrane into the lumen.

29
Q

What is diuresis?

A

Increased excretion of dilute urine

30
Q

At a cellular level how is NaCl reabsorbed in thick ascending limb?

A

Through Na+ K+ 2Cl- symporter

31
Q

At a cellular level how is NaCl reabsorbed in the DCT?

A

Through Na+ K+ ATPase pump, Na+ is pumped into blood

32
Q

Where are principal cells found?

A

In the collecting duct.

33
Q

What causes central diabetes insipidus?

A

Decreased/negligent production and release of ADH.

34
Q

Clinical features of central diabetes insipidus?

A
  • Polyuria- large urine volume
  • Polydipsia- thirst
35
Q

How do you treat central diabetes insipidus?

A

External ADH

36
Q

What causes/ is Nephrogenic Diabetes Insipidus?

A

Correct amount of ADH produced but something going wrong at collecting duct?
- Fewer/mutant AQP2
- Mutant V2 receptors

37
Q

How do you treat nephrogenic diabetes insipidus?

A
  • Thiazide diuretics- reduce filtration rate at Bowman’s capsule so less blood filtered so less urine produced
  • NSAIDs
38
Q

What is Symptom of inappropriate ADH secretion (SIADH)?

A

Increased unnecessary production and release of ADH

39
Q

Clinical features of Symptom of inappropriate ADH secretion (SIADH)?

A
  • Hyperosmolar urine
  • Hypervolemia
  • Hyponatremia
40
Q

How do you treat Symptom of inappropriate ADH secretion (SIADH)?
Giving two examples.

A

Non peptide inhibitor of ADH receptor (conivaptan and tolvaptan)

41
Q

What do the kidneys do to help maintain blood ph?

A
  • Reabsorption of 100% of HCO3-
  • Production of new HCO3-
  • Helps secrete and excrete H+ ions
42
Q

What is the enzyme that converts CO2 and H2O into carbonic acid? (H2CO3)

A

Carbonic anhydrase

43
Q

What is an acid-base disorder due to changes in PCO2 called?

A

Respiratory disorder

44
Q

What is an acid-base disorder due to changes in HCO3- conc called?

A

Metabaolic disorder.

45
Q

Where is most of the HCO3- reabsorbed in the nephron?

A

80% in the PCT

46
Q

What does alpha intercalated cell do?

A

HCO3- reabsorption and H+ secretion

47
Q

What does beta intercalated cell do?

A

HCO3- secretion and H+ reabsorption

48
Q

Describe how new HCO3- is produced at PCT

A

1) glutamine molecules gives 2 NH4+ molecules and 1 divalent ion (A2-) which gives rise to 2 HCO3-

2) The 2 NH4+ is excreted into tubular fluid
- Through Na+ H+ antiporter (NH4+ substitutes in place of H+)
- Turns into NH3 and moves into tubular fluid where it combines with a H+ to form NH4+ again

49
Q

How is metabolic acidosis characterised?

A

Decrease in HCO3- conc leading to decrease in pH

50
Q

What is the compensatory response for metabolic acidosis

A
  • Increased (hyper)ventilation which kicks in first → PCO2 goes down so H+ conc goes down
  • Increased HCO3- conc reabsorption and production to compensate for decrease in conc
51
Q

How is metabolic alkalosis characterised?

A

Increased HCO3- conc leading to increased pH

52
Q

What is the compensatory response for metabolic alkalosis?

A
  • Decreased (hypo)ventilation which kicks in first → PCO2 goes up so H+ conc goes up
  • Increased HCO3- conc excretion to compensate for increase in conc
53
Q

How is respiratory acidosis characterised?

A

Increased PCO2 leading to lower pH

54
Q

How is respiratory alkalosis characterized?

A

Decreased PCO2 leading to higher pH

55
Q

What is a normal HCO3- conc?

A

24mEq/L (REMEMBER THE NUMBER)

56
Q

What is a normal blood pH?

A

7.4

Urology and renal medicine (5 decks)

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