How does the body maintain pH?

Internal pH 7.35-7.45

Acid-base buffer systems (1st line of defense)

Metabolic sources of hydrogen ions

Concentration of H+ at equilibrium determines pH

Aerobic respiration of glucose

Carbonic acid

Anaerobic respiration of glucose

Lactic acid

Incomplete oxidation of fatty acids

Acidic ketone bodies

Oxidation of sulfur-containing amino acids

Sulfuric acid

Hydrolysis of phosphoproteins and nucleic acids

Phosphoric acid

Bicarbonate system

Phosphate system

Protein system

Bicarbonate ion

Carbonic acid

Converts a strong acid into a weak acid

Converts a strong base into a weak base

Monohydrogen phosphate ion

Dihydrogen phosphate

Converts a strong acid into a weak acid

Converts a strong base into a weak base

NH3+ group of an amino acid or protein

Releases a hydrogen ion in the presence of excess base

-COO group of an amino acid or protein

Accepts a hydrogen ion in the presence of excess acid

Elimation of excess bases or acids (2nd line of defense)

Renal mechanism

Excretion of hydrogen ions through urine

Respiratory mechanism

Excretion of carbon dioxide

Control of rate and depth of breathing

Acid-base imbalances

Alkalosis

Acidosis

Respiratory

Metabolic

Decreased rate and depth of breathing

Obstruction of airway

Decreased gas exchange

Accumulation of CO2

Kidney failure to excrete acids

Excessive production of acidic ketones as in diabetes mellitus

Prolonged diarrhea with loss of alkaline intestinal secretions

Prolonged vomiting with loss of intestinal secretions

Accumulation of nonrespiratory acids

Excessive loss of bases

Respiratory

Metabolic

Anxiety, fever, poisoning, high altitude

Hyperventilation

Excessive loss of CO2

Decrease in concentration of H2CO3

Decrease of H+ concentration

Gastric drainage, vomiting with loss of gastric secretions, certain diuretics

Excess ingestion or administration of antacids

Loss of nonrespiratory acids

Gain of bases