Acid-base disorders

Question 1

What is the hydrogen ion concentration in the body if it is at pH 7.4?

Answer 1

40nmol/L

Question 2

Why is important to keep the body at its optimum pH?

Answer 2

It keeps enzymes working at their optimum levels

Question 3

Approximately 60mmols of waste hydrogen ions are produced each day, how are they made?

Answer 3

Through the oxidation of sulphur containing amino acids, incomplete metabolism during anaerobic glucose metabolism and ketone body formation. If it goes unchecked it would leak into ECF and rise to 4mmols/L being 100,000 times more acidic than normal

Question 4

How does the body stop the buildup of waste hydrogen ions?

Answer 4

When produced they are quickly collected up by buffers and taken to the kidneys to be removed via urea

Question 5

What is a buffer?

Answer 5

A solution of weak acid and its salt that can resist change in pH

Question 6

How does CO2 influence the pH balance?

Answer 6

CO2, when dissolved in water gets converted into carbonic acid, which will decrease the pH if it builds up. To stop this the CO2 is collected up by haemoglobin in the RBCs and taken to the lungs to be expired

Question 7

What is the most common buffer in the body?

Answer 7

The bicarbonate-carbonic acid buffer that makes up 70% of the total plasma buffering capacity

Question 8

Can haemoglobin aid in pH balance?

Answer 8

Yes, when in RBCs it can act as a buffer and has a negative charge so can mop up hydrogen ions

Question 9

Explain bicarbonate recovery (long answer)

Answer 9

Bicarbonate recovery is a mechanism used to regulate bicarbonate levels in the body. The bicarbonate will bind with hydrogen in the glomerulus to form carbonic acid, which will then be split up into water and CO2, the CO2 will diffuse along its conc gradient into the renal tubular cells, combining with water again to form carbonic acid. It will then split the last time into bicarbonate and hydrogen. The bicarbonate will diffuse back into the interstitial fluid, while the hydrogen will be actively secreted into the glomerulus in exchange for sodium, completing the cycle.

Question 10

Explain bicarbonate regeneration

Answer 10

This mechanism is very similar to bicarbonate recovery, except that it results in a net loss of hydrogen ions from the body. It uses ammonia and phosphate as buffers. But for each hydrogen ion lost one bicarbonate is generated and returned to the ECF.

Question 11

How is ammonia produced during bicarbonate regeneration?

Answer 11

Ammonia is produced in the renal tubular cells via the hydrolysis of the amino acid glutamine to glutamate

Question 12

What is compensation? and what are the different forms of it?

Answer 12

Compensation is a physiological response to correct the balance of hydrogen ions. The four forms are renal, respiratory, partial and full

Question 13

What can cause metabolic acidosis?

Answer 13

Increased hydrogen formation (ketoacidosis), decreased hydrogen excretion (chronic renal failure), acid ingestion (excessive intake of amino acids) and loss of bicarbonate from the body (diarrhoea)

Question 14

How would you treat severe acidosis?

Answer 14

Determine the underlying cause of the acidosis as well as the administration of bicarbonate

Question 15

What can cause metabolic alkalosis?

Answer 15

Gastrointestinal loss of hydrogen (vomiting), renal loss of hydrogen (conns and cushings syndrome), administration of alkali, hypoventilation

Question 16

What can cause respiratory acidosis?

Answer 16

Airway obstruction, inhibition of respiratory centre, neuromuscular diseases, pulmonary diseases. depending on the cause can be acute or chronic

Question 17

What can cause respiratory alkalosis?

Answer 17

Hypoxia, pulmonary diseases, increased respiration (salicylates), not as common respiratory acidosis