Regulation of Blood pH and Acid-Base Balance

Importance of pH in the Body

• pH Indicator: Measures acidity.
• Blood pH Range: 7.35 - 7.45 (strict regulation required).
• Consequences of pH Changes: Minor changes affect protein stability and biochemical processes.

Carbon Dioxide and Acid-Base Equilibrium

• Metabolism and CO2: Normal metabolism produces CO2, combining with water to form carbonic acid.
• Chemical Equation: CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3- (carbonic acid dissociates into hydrogen ions and bicarbonate).
• Equilibrium: Co-existence of components; concentration changes shift equilibrium.
• Impact on pH: Increase in H+ leads to increased acidity and lower pH.

Mechanisms to Regulate Blood pH

• Pulmonary Regulation:
  • Role of Exhalation: CO2 elimination reduces blood acidity.
  • Chemoreceptors: Detect pH decrease, trigger deeper, faster breathing.
  • Speed: Fast, effective within minutes to hours.
• Renal Regulation:
  • Hydrogen Ion Excretion & Bicarbonate Reabsorption: Adjusts blood pH by acid excretion and bicarbonate reuptake.
  • Speed: Slower, takes days to respond.
  • Proximal Tubule: Reabsorbs filtered bicarbonate.
  • Collecting Duct: Generates new bicarbonate, actively secretes acids.
  • Buffers: Phosphate and ammonia combine with hydrogen ions for excretion.

Role of Buffers and Other Factors

• Ammonia Buffering System: Adjusts to acid changes, flexible concentration increase.
• Influences on Acid Excretion: Blood pH, potassium, chloride concentration, hormones.

Acid-Base Disturbances

• Acidosis: Process increasing acidity.
• Alkalosis: Process increasing alkalinity.
• Multiple Processes: Patients may have simultaneous opposite processes.

Types of Acidosis

• Respiratory Acidosis: Caused by lung function inadequacy, CO2 accumulation.
• Metabolic Acidosis: Caused by excess metabolic acids, reduced kidney excretion, acid ingestion, or alkali loss. Characterized by decreased plasma bicarbonate.

Types of Alkalosis

• Respiratory Alkalosis: Caused by increased ventilation, excessive CO2 exhalation.
• Metabolic Alkalosis: Caused by excess acid loss, bicarbonate retention, or alkali ingestion. Characterized by increased plasma bicarbonate.