Acid-base balance

Question 1

What are the normal values of pH and [H+]?

Answer 1

pH - 7.4

[H+] = 40nmol/l

Question 2

Give 4 ways each for gain and loss of H+

Answer 2

GAIN = from CO2 in aerobic resp
protein met
loss of HCO3- in diarrhoea
loss of HCO3- in urine

LOSS 
CO2 excreted through lungs
use of H+ in met
loss of H+ in vomitus
loss of H+ in urine

Question 3

What can act as buffers besides HCO3-?

Answer 3

Intra- and extracellular B- (from HB is bound to H)

Question 4

What are 3 mechanisms of pH homeostasis?

Answer 4

1. Buffers

2. Renal regulation of H+ and HCO3-

Question 5

How can the kidneys correct for:
Acidaemia?
Alkalaemia?

Answer 5

Acidaemia - increase H+ secretion (in urine) and adding new HCO3- to blood to lower plasma H+

Alkalaemia - inhibiting H+ secretion (by lowering HCO3- reabsorption), so excreting HCO3- in urine to inc plasma H+

Question 6

How can the kidney produce new bicarbonate ions?

Answer 6

Ammoniagenesis (glutamine metabolism)

Question 7

Explain ammonium trapping

Answer 7

Ammonium is produced by glutamine and moved into the tubular lumen in exchange by Na+. Once moved into the lumen, the ammonium ion is trapped in the lumen bc no transporters

Question 8

Where does ammoniagenesis mainly happen?

Answer 8

In proximal convoluted tubule

Question 9

In which part of the nephron is H+ secretion most important?

Answer 9

LDT and collecting duct

Question 10

Ammonium trapping
Which part of the nephron is NH4+ reabsorbed?
Which part does NH3 diffuse into? What role does NH3 serve?

Answer 10

thick limb of loop of henle

NH3 diffuses into lumen of collecting duct
in CD acts as a buffer

Question 11

What cell can also make new HCO3-

Answer 11

intecalated cells from CO2 and water to help in acidosis

Question 12

What are 3 methods of removing extra H+?

Answer 12

1. release directly via urine as free H+
2. buffer using phosphate
3. ammonia buffering

Question 13

What changes must occur for:
Respiratory acidosis/alkalosis?
Metabolic acidosis/alkalosis?

Answer 13

respiratory acidosis - hypoventilation (increases pCO2)
respiratory alkalosis- hyperventilation
met acidosis - ingestion of H+ or loss of HCO3-
met alkalosis

Question 14

Respiratory Acidosis w/ metabolic compensaton – what are the changes? Same for resp alkalosis w/ metabolic compensation

Answer 14

acidosis - renal compensation, new HCO3- in blood
alkalosis - renal compensation, inc HCO3- excretion, dec H+ excretion
mat acid - resp compensation (hyperventilation)
met alk- dec HCO3- reabsorption, hypoventilation

Question 15

What can cause:
Respiratory Alkalosis & Acidosis
Metabolic Alkalosis & Acidosis

Answer 15

resp alk - drugs, CNS disorders, anxiety, fear
resp acid- COPD, drug induced depression of resp centres
met alk - antacids, vomiting, primary hyperaldosteronism
met acid - uncontrolled diabetes - ketoacidosis or diarrhoea

Question 16

If you have metabolic acidosis or alkalosis, does resp system correct fully?

Answer 16

no, unsustainable (turn hypoxic

Question 17

Why can’t you correct an alkalosis with vomiting?

Answer 17

Vomitus contains water, HCL and KCL and resulting hypochloraemic volume depletion results in kidney retaining Na+ and necessarily HCO3- and so not compensating the disorder