Question

Discuss in detail how the ph of the blood is regulated. Describe 2 situations in which ph levels might be abnormal and what would occur in the in the body to compensate for these alterations.

Answer 1

I am describing main 4 pH alteration.

Normal blood pH is 7.35 - 7.45.

Below 7.35 is acidosis , Above 7.45 is Alkalosis.

1. Respiratory acidosis.

The primary defect in respiratory acidosis is due to retention of CO2(H2CO3 increase).

There may be several causes for respiratory acidosis which include depression of the respiratory enter ,pulmonary dosorders and breathing air with high content of CO2.

Renal mechanism comes for the rescue to compensate respiratory acidosis.

More HCO3- is generated and retained by the kidneys which adda up to the alkali reserve of the body.

2. Metabolic alkalosis.

The primary abnormality in metabolic alkalosis is an increase in HCO3- concentration.

This may occur due to excessive vomiting or an excessive intake of sodium bicarbonate for therapeutic purpose.

Metabolic alkalosis is commonly associated with low K+ concentration.

in severe K+ deficiency , H+ ions are retained inside the cells to replace missing K+ ions.

In the renal tubular cells , H+ ions are exchanged with the reabsorbed Na+ .

The respiratory mechanism initiates the compensation by hypoventilation to retain CO2 ( hence H2CO3 increase) . This is slowly taken over by renal mechanism which excretes more HCO3- and retain H+.



3. Respiratory alkalosis.

Respiratory alkalosis.

B.

Main effects.

Depression of respiratory drive.

Left shift of oxyhemoglobin dissociation.

Peripheral vasoconstriction.

Arrhythmias.

Decreased cardiac output.

Decreased cerebral perfusion.

Respiratory alkalosis

The primary abnormality in respiratory alkalosis is a decrease in H2CO3 concentration.

This may occur due to prolonged Hyperventilation resulting in increased exhalation of CO2 by the lungs.

Hyperventilation is observed in conditions such as hysteria , hypoxia , raised intracranial pressure , excessive artificial ventilation and the action of certain drugs (salicylate ) aspirin that stimulate respiratory center.

COmpensatory mechanism.

The renal mechanism tries to compensate by increasing the urinary excretion of HCO3- .


4.
Metabolic acidosis.

The primary defect in metabolic acidosis is a reduction in bicarbonate concentration , which leads to a fall in blood pH.

The bicarbonate concentration may be decreased due to its utilization in buffering H+ ions , loss in urine or gastrointestinal tract or failure to be regenerated.

The most important cause of metabolic acidosis is due to an excessive production of organic acids which combine with NaHCO3 and deplete the alkali reserve .Metabolic acidosis is commonly seen in Severe uncontrolled diabetic mellitus which is associated with excessive production of acetoacetic acid and beta hydroxybutyric acid.

Compensation f Metabolic acidosis.

The acute metabolic acidosis is usually compensated by hyperventilation of lungs.

This leads to an increased elimination of CO2 from the body( hence H2CO3 decrease ).