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Flashcards in Physiology 8 (easy) Deck (11)
1

Normal plasma pH

7.4

2

Normal [HCO3]p

25 mmol/l

3

Normal arterial PCO2

40mmHg

4

Compensation vs correction of an A-B disturbance

Compensation is the restoration of pH irrespective of what happens to [HCO3-]p and PCO2

Correction of an A-B disturbance is restoration of pH and [HCO3-]p and PCO2 to normal

5

Give examples of when CO2 is retained by body

Chronic bronchitis
Chronic emphysema
Airway restriction (bronchial asthma, tumour)
Chest injuries
Respiratory depression

6

PCO2 and H+

PCO2 drives H+ secretion by the kidney
(therefore, CO2 retention stimulates H+ secretion into the filtrate)

7

Why does [HCO3]p rise in respiratory acidosis?

Rises because of a) the disorder (see equation) and b) as a result of renal compensation

-correction requires lowering pCO2 by restoration of normal ventilation

8

Causes of respiratory alkalosis

Low inspired PO2 at altitude (hypoxia stimulates peripheral chemoreceptors, hyperventilation lowers PCO2)
Hyperventilatio (fever, brainstem damage)
Hysterical overbreathing

9

What is metabolic acidosis?

Excess H+ from any source other than CO2

10

Causes of metabolic acidosis

Ingestion of acids or acid-producing foodstuffs

Excessive metabolic production of H+ (e.g. lactic acid during exercise or ketoacidosis)

Excessive loss of base from the body (e.g. diarrhoea – loss of HCO3-)

11

Causes of metabolic alkalosis

Loss of HCl from the stomach (vomiting)

Ingestion of alkali or alkali-producing foods
(e.g. Ingestion of NaHCO3 as an antacid, though not a problem with modern antacids)

Aldosterone hypersecretion
(causes stimulation of Na+/H+ exchange at the apical membrane of the tubule; acid secretion)