Regulation of Acid-Base Balance

Question 1

What is the role of kidneys in acid-base balance (3)?

Answer 1

• Secretion & excretion of H⁺
• Reabsorption of HCO₃^-
• Production of new HCO₃^-

Question 2

What is the role of bicarbonate ions in acid-base regulation?

Answer 2

Act as a buffer

Question 3

How can the Henderson-Hasselbalch equation be used to identify the cause of an alkalaemia / acidaemia?

Answer 3

Question 4

What is an intercalated cell?

Answer 4

• Secretes or absorbs acid / bicarbonate
  
  • Regulation of blood pH
  • Intercalated cells reabsorb K⁺ & HCO₃^-, while secreting H⁺ or vice versa
    
    • This function reduces / increases the acidity of the plasma, and subsequently increases / decreases urine acidity; this mechanism is achieved by carbonic anhydrase activity
  • Mitochondrial rich

Question 5

What are the 2 types of intercalated cells?

Answer 5

• Alpha
• Beta

Question 6

What is the function of the alpha intercalated cells?

Answer 6

• HCO₃^- reabsorption & H⁺ secretion

Question 7

What is the function of beta intercalated cells?

Answer 7

• HCO₃^- secretion & H⁺ reabsorption

Question 8

Outline the reabsorption of bicarbonate ion in PCT

Answer 8

Question 9

Outline the reabsorption of bicarbonate ion in DCT & CD

Answer 9

Question 10

How is bicarbonate transported into the interstitium through the basolateral surface?

Answer 10

• NBC-1 transporter

Question 11

Outline the production of new bicarbonate in PCT.

Answer 11

Question 12

Which amino acid within intercalated cells is used as a mediator for ammonia release?

Answer 12

• Glutamine

Question 13

How is ammonia transported into the filtrate?

Answer 13

• NHE3 anti-porter

Question 14

What happens to ammonia when in the filtrate?

Answer 14

• Ammonia is protonated by hydrogen ions in the filtrate to form ammonium ions
• The bicarbonate that dissociated from glutamine enters circulation

Question 15

What does carbonic acid dissociate into?

Answer 15

• Bicarbonate and hydrogen ions

Question 16

Which transporters secrete hydrogen ions into the tubular fluid?

Answer 16

• NHE2 transporters

Question 17

Outline the production of new bicarbonate in DCT & CD.

Answer 17

Question 18

Which ion behaves as a urinary buffer in the tubular fluid?

Answer 18

• Phosphate ions

Question 19

Identify the acid-base disorder:
pH=7.2
HCO₃^-= 17 mEq/L
PCO₂= 35 mmHg

Answer 19

Metabolic acidosis

Question 20

Identify the acid-base disorder:
pH=7.5
HCO₃^-= 17 mEq/L
PCO₂= 35 mmHg

Answer 20

Respiratory alkalosis

Question 21

Ms L, a 25-year-old healthy woman on her holiday develops stomach infection with nausea and vomiting.
Following data was collected for her: Blood pH = 7.1, [HCO₃^-] = 16mEq/L, PCO₂= 30mmHg.
Identify the compensatory mechanism being used by her body.
[Normal values: Blood pH=7.4, [HCO₃^-] = 24mEq/L, PCO₂= 40mmHg]

Options:
1. Renal compensation – Reduced reabsorption of Bicarbonate ions
2. Renal compensation – Reduced excretion of ammonia and proton ions
3. Respiratory compensation – Hypoventilation
4. Respiratory compensation – Hyperventilation

Answer 21

Respiratory compensation – Hyperventilation

Question 22

Ms S, a 25-year-old woman while trekking the Himalayas develops symptoms of dizziness and pain.
Following data was collected for her: Blood pH = 7.6, [HCO₃^-] = 16mEq/L, PCO₂= 25mmHg.
Identify her acid-base disorder.
[Normal values: Blood pH=7.4, [HCO₃^-] = 24mEq/L, PCO₂= 40mmHg]

1. Metabolic alkalosis
2. Respiratory alkalosis
3. Metabolic acidosis
4. Respiratory acidosis

Answer 22

Respiratory alkalosis

Question 23

Ms J, a 25-year-old woman with a history of asthma, on her holiday develops stomach infection with diarrhoea.
Following data was collected for her: Blood pH = 7.1, [HCO₃^-] = 16mEq/L, PCO₂= 45mmHg.
Identify her acid-base disorder.
[Normal values: Blood pH=7.4, [HCO₃^-] = 24mEq/L, PCO₂= 40mmHg]
1. Metabolic acidosis
2. Respiratory acidosis
3. Mixed alkalosis
4. Mixed acidosis

Answer 23

Mixed acidosis