Acid-Base Balance Disorders: pH Homeostasis in the Body

Study Notes

pH Homeostasis

pH of blood is tightly controlled between 7.35-7.45
Acidosis (acidemia) occurs when pH is below 7.35
Alkalosis (alkalemia) occurs when pH is above 7.45
Small changes in pH can lead to disturbances in enzyme function, hormone and receptor function, and muscle, heart, and nervous system function

Defence Mechanisms

Buffer systems: weak acid and base pairs that bind or release H+ ions to maintain pH
Respiratory system: regulates CO2 levels, which affects pH
Kidneys: regulate acid-base balance by reabsorbing and regenerating bicarbonate, excreting hydrogen ions, and eliminating large amounts of acids

Buffer Systems

Bicarbonate buffer system: NaHCO3/H2CO3, main buffer in extracellular fluid
Hemoglobin buffer system: HbO2/Hb
Phosphate buffer system: HPO4/H2PO4
Protein buffer system: carboxyl and amino groups

Respiratory System

Concentration of carbonic acid directly proportional to pCO2
Body pH can be adjusted by changing rate and depth of breathing

Kidneys Regulation

Reabsorb and regenerate bicarbonate
Excrete bases and eliminate large amounts of acids
Failures in kidney function lead to pH balance failures

Acid-Base Balance Parameters

pH: 7.35-7.45
pCO2: 36-44 mmHg (40 mmHg)
HCO3: 22-26 mmol/L (24 mmol/L)
BE (base excess): 0±2
Other parameters: Na+, K+, Ca2+, Mg2+, Cl-, lactate, total proteins, albumin, urea, creatinine, glycemia, anion gap

Acid-Base Balance Disorders

Metabolic disorders: acidosis (decrease in pH) and alkalosis (increase in pH)
Respiratory disorders: acidosis (increase in pCO2) and alkalosis (decrease in pCO2)
Combined disorders: metabolic acidosis and respiratory alkalosis, metabolic alkalosis and respiratory acidosis

Compensation and Correction

Compensation: mechanisms that help restore pH balance
Correction: complete restoration of pH balance
Respiratory compensation: hyperventilation or hypoventilation to change CO2 levels
Metabolic compensation: kidneys regulate acid-base balance by reabsorbing and regenerating bicarbonate, excreting hydrogen ions, and eliminating large amounts of acids

Metabolic Acidosis

Bicarbonate deficit: HCO3- < 22 mmol/L
Causes: accumulation of acids, kidney failure, loss of bicarbonate, intoxication with acids
Compensation: increased ventilation, renal excretion of hydrogen ions, potassium exchange with excess hydrogen ions

Metabolic Alkalosis

Bicarbonate excess: HCO3- > 26 mmol/L
Causes: excessive vomiting, excessive use of alkaline drugs, certain diuretics, endocrine disorders, severe dehydration
Compensation: decreased ventilation, difficult due to limited hypoventilation

Respiratory Acidosis

Carbonic acid excess: pCO2 > 45 mmHg
Causes: chronic conditions (depression of respiratory center, paralysis of respiratory or chest muscles, emphysema) and acute conditions (ARDS, pulmonary edema, pneumothorax, asphyxia)
Compensation: metabolic compensation by kidneys

Respiratory Alkalosis

Carbonic acid deficit: pCO2 < 35 mmHg
Causes: hyperventilation, oxygen deficiency at high altitude, pulmonary disease, fever, acute anxiety, early salicylate intoxication, cirrhosis, Gram-negative sepsis
Compensation: kidneys decrease secretion of hydrogen ion and excrete bicarbonate ion

Description

Test your understanding of acid-base balance disorders, including acidosis and alkalosis, and how they affect the body's pH levels, enzymes, hormones, and electrolytes. Learn about the importance of pH homeostasis and its impact on muscle and heart function.