Acid-Base Balance in Anatomy & Physiology

Learning Objectives

• Identify the most powerful and most rapid buffer systems in the body.
• Describe protein buffer systems.
• Explain how the respiratory system affects blood pH.
• Describe the kidney's role in maintaining acid-base balance.

Overview

• Proper function requires a tight balance of acids and bases in the blood, measured by the pH scale.
• Buffers prevent radical changes in pH by absorbing hydrogen or hydroxyl ions.
• Common buffers: weak acids/bases absorb excess ions.

Buffer Systems in the Body

• Chemical Buffers: Fast-acting (seconds) adjustments in blood.
• Respiratory System: Adjusts blood pH by exhaling CO2 (minutes).
• Renal System: Adjusts through hydrogen ion excretion and bicarbonate conservation (hours to days).

Types of Buffer Systems

• Protein Buffers:

  • Proteins are excellent buffers due to amino acids that bind ions.
  • Hemoglobin buffers hydrogen ions during CO2 to bicarbonate conversion.

• Phosphate Buffer:

  • Two forms: sodium dihydrogen phosphate (weak acid) and sodium monohydrogen phosphate (weak base).
  • Strong acids/bases convert into weak acids/bases, preventing pH change.

• Bicarbonate-Carbonic Acid Buffer:

  • Key buffer in blood; involves bicarbonate and carbonic acid.
  • Works by capturing ions to prevent significant pH changes.
  • Major role in buffering metabolic wastes such as lactic acid.

Respiratory Regulation of Acid-Base Balance

• CO2 and Blood pH: CO2 reacts with water to form carbonic acid, influencing pH.
• Breathing Adjustments: Changes in breathing rate regulate CO2, adjusting pH.
  • Hyperventilation decreases CO2, raising pH (alkalosis).
  • Hypoventilation increases CO2, lowering pH (acidosis).

Renal Regulation of Acid-Base Balance

• Bicarbonate Conservation:

  • Bicarbonate ions in the filtrate are converted to CO2 to pass into cells.
  • Reconverted into bicarbonate and returned to blood.

• Ion Exchange:

  • Sodium reabsorbed, hydrogen ions expelled in exchange.
  • Hydrogen ions form water or are excreted.

• Role in pH Balance:

  • Competes with ions like potassium for exchange with sodium.
  • Chloride loss prompts bicarbonate conservation.

Disorders and Conditions

• Ketoacidosis:
  • Occurs in poorly controlled diabetes.
  • Involves excess acid production from fatty acid breakdown.
  • Symptoms: fruity breath, rapid breathing, dry skin, and more.

Chapter Review

• Multiple buffer systems maintain blood pH between 7.35 - 7.45.
• Respiratory and renal systems crucial in managing acid-base balance.

Glossary

• Hypercapnia: Elevated CO2 levels in blood.
• Hypocapnia: Low CO2 levels in blood.