Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

UROLOGY AND RENAL MEDICINE 2 > RENAL REGULATION OF WATER AND ACID BASE BALANCE > Flashcards

RENAL REGULATION OF WATER AND ACID BASE BALANCE Flashcards

1
Q

How do you calculate osmolarity?

A

Concentration x no. of dissociated particles

100mmol/L NaCl = 200 mOsm/L

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How is body fluid distributed?

A

2/3 intracellular fluid

1/3 extracellular:

  • 95% interstitial fluid
  • 25% intravascular fluid
  • 5% transcellular fluid
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Give examples of unregulated water loss

A

Sweat
Faeces
Vomit
Water evaporation from respiratory lining and skin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

In which parts of the nephron does water reabsorption occur?

A

DCT (67%)
Thin descending limb (15%)
Thin ascending limb
Collecting duct

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

In which parts of the nephron does Na+ Cl- reabsorption occur?

A

Thin ascending limb (passive)

Thick ascending limb (active)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is countercurrent multiplication?

A

Allows the continued reabsorption of water and production of concentrated urine

Thick ascending limb actively pumps salt out into interstitial fluid which becomes hyperosmolar.
Passive water reabsorption from descending limb due to this concentration gradient so equilibrium is reached.

New tubular fluid enters descending limb and pushes the relatively hyperosmolar fluid down.

These 2 steps repeat and the osmotic gradient of the medullary interstitium forms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How does urea recycling work and what does it result in?

A

Some urea in the collecting duct is reabsorbed into the interstitium by UT-A1 and UT-A3.

The urea then is either transported into the vasa recta by UT-B1 or re-enters the thin descending limb by UT-A2 to make its way back to the collecting duct.

Urine concentration occurs due to increased interstitium osmolarity.
Urea excretion requires less water since urea levels in collecting duct equilibrate with interstitium levels (600 mmol/L) so more urea excreted in same amount of water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the vasa recta?

A

Blood capillaries surrounding nephron

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the effects of vasopressin/AVP/ADH on urea recycling?

A

Increases UT-A1/A3 levels so more urea is reabsorbed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What factors stimulate ADH production and release?

A 
Increased plasma osmolarity
Decreased BP
Hypovolemia
Nausea
Angiotensin II
Nicotine
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What factors inhibit ADH production and release?

A 
Decreased plasma osmolarity
Increased BP
Hypervolemia
Ethanol
Atrial natriuretic peptide
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How is plasma osmolarity detected?

A

Osmoreceptors in hypothalamus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How is blood pressure detected?

A

Baroreceptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How does ADH work?

A

Binds to G linked V2 receptor on basolateral membrane of collecting duct cell. Increases aquaporin-2 channels on apical membrane and aquaporin-3 channels on basolateral membrane allowing increased water reabsorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

During diuresis how does the nephron increase dilute urine excretion?

A

NaCl reabsorption in thick ascending limb by apical Na+/K+/2Cl- symporter, basolateral Na+/K+ ATPase pump and K+/Cl- symporter

NaCl reabsorption in distal convoluted tubule by apical Na+/Cl- symporter, basolateral Na+/K+ ATPase pump and K+/Cl- symporter

Na+ reabsorption in collecting duct principal cells by apical Na+ ion channel and basolateral Na+/K+ ATPase pump.

Some water is still reabsorbed in the collecting duct even with 0 ADH due to paracellular pathways

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

During antidiuresis how does the nephron increase concentrated urine in low volume excretion?

A

High ADH supports Na+ reabsorption:

  • Increased Na+/K+/2Cl- symporter (thick ascending)
  • Increased Na+/Cl- symporter (DCT)
  • Increased Na+ channel (collecting duct)

This increases interstitium osmolarity so more water can be reabsorbed

Aquaporin channels in DCT and collecting duct
As you go down collecting duct more and more water is reabsorbed due to interstitial gradient

17
Q

Name 3 ADH related disorders

A

Central diabetes insipidus
Syndrome of inappropriate ADH secretion (SIADH)
Nephrogenic diabetes insipidus

18
Q

What is the cause, clinical features and treatment of central diabetes insipidus?

A

Cause: Decreased/negligent production and release of ADH (genetic)

Clinical features: Polyuria, polydipsia

Treatment: External ADH

19
Q

What is the cause, clinical features and treatment of SIADH?

A

Cause: Increased production/release of ADH

Clinical features: Hyperosmolar urine, hypervolemia, hyponatremia

Treatment: Non-peptide inhibitor of ADH receptor (conivaptan, tolvaptan)

20
Q

What is the cause, clinical features and treatment of nephrogenic diabetes insipidus?

A

Cause: Less/mutant AQP2, mutant V2 receptor

Clinical features: Polyuria, polydipsia

Treatment: Thiazide diuretics (paradoxical - reduces eGFR), NSAIDs

21
Q

What causes the need for acid-base balance?

A

Acid and base derived from diet and metabolism

Base excretion in faeces so need to neutralise net addition of metabolic acid

22
Q

Which organ carries out acid-base balance and how do they do it?

A

Kidneys

  • Secretion and excretion of H+
  • Reabsorption of HCO3- (almost 100%)
  • Production of new HCO3-
23
Q

What should the ECF concentration of HCO3- be?

A

24 mEq/L

24
Q

Where are bicarbonate ions reabsorbed in the nephron?

A

PCT (80%)
Thick ascending limb (10%)
DCT (6%)
Collecting duct (4%)

25
Q

What is the relationship between [H+] and [HCO3-]

A

[H+] is inversely proportional to [HCO3-]

26
Q

How is HCO3- reabsorbed in the PCT?

A

CO2 enters cell from tubular fluid via diffusion.
Reacts with water catalysed by carbonic anhydrase

H+ formed is secreted by:

  • Na+/H+ antiporter
  • H+ ATPase pump

HCO3- formed is reabsorbed by:
- Na+/HCO3- symporter

27
Q

How do alpha intercalated cells of DCT and collecting duct contribute to acid base balance?

A

HCO3- reabsorption and H+ secretion

H+ formed is secreted by:

  • H+ ATPase pump
  • H+/K+ ATPase

HCO3- formed is reabsorbed by:
- Cl-/HCO3- antiporter

28
Q

How do beta intercalated cells of DCT and collecting duct contribute to acid base balance?

A

HCO3- secretion and H+ reabsorption

HCO3- secreted by:
- Cl-/HCO3- antiporter

H+ reabsorbed by:
- H+ ATPase pump

29
Q

Where does new bicarbonate ion production occur?

A 
PCT
DCT (alpha intercalated cell)
Collecting duct (alpha intercalated cell)
30
Q

How do cells in the PCT produce new bicarbonate ions?

A

Glutamate into 2NH4+ and a divalent ion

Divalent ion into 2HCO3- and reabsorbed into blood
NH4+ secreted by:
- Na+/H+ antiporter (ammonia replaces H+)
- Into NH3 which diffuses through

NH3 then react with H+ in tubular fluid and excreted with rest of NH4+

Ammonia cannot enter blood because if it does it goes to liver where its converted to a urea ion and H+. The H+ will require a HCO3- for neutralisation so no net gain of HCO3-

31
Q

How do the alpha intercalated cells of the DCT and collecting duct produce new bicarbonate ions?

A

H20+CO2 –> H+ + HCO3- in cell
HCO3- into blood by apical Cl-/HCO3- antiporter.

H+ into tubular fluid by:

  • H+ ATPase pump
  • H+ K+ ATPase

In tubular fluid HPO4 2- acts as a non-bicarbonate buffer reacting with the H+ forming H2PO4- and excreted

32
Q

What are the characteristics of metabolic acidosis/alkalosis?

A

Metabolic acidosis: Decreased [HCO3-] and pH

Metabolic alkalosis: Increased [HCO3-] and pH

33
Q

What are the characteristics of respiratory acidosis/alkalosis?

A

Respiratory acidosis: Increased pCO2 and decreased pH

Respiratory alkalosis: Decreased pCO2 and increased pH

34
Q

What is the compensatory response to metabolic acidosis?

A

Hyperventilation to decrease pCO2 which decreases [H+] and increases pH

Increased HCO3- reabsorption and production

35
Q

What is the compensatory response to metabolic alkalosis?

A

Hypoventilation to increase pCO2 which increases [H+] and decreases pH

Increased HCO3- excretion

36
Q

What is the compensatory response to respiratory acidosis?

A

Acute:
- Intracellular buffering (CO2 enters cell and into H+ + HCO3- via carbonic anhydrase, H+ is neutralised by proteins so net gain of HCO3-, HCO3- is transported back to blood to help with decreasing pH)

Chronic:

  • Increased HCO3- reabsorption and production
  • Increased excretion of H+/NH4+
37
Q

What is the compensatory response to respiratory alkalosis?

A

Acute:
- Intracellular buffering (H2CO3 –> H+ + HCO3-) backwards reaction increasing carbonic acid so less HCO3-

Chronic:
- Decrease reabsorption and production of HCO3-

UROLOGY AND RENAL MEDICINE 2 (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions