Lecture Notes: Acid-Base Balance in Anatomy & Physiology

Learning Objectives

• Understand the most powerful and rapid buffer systems in the body
• Describe protein buffer systems
• Explain respiratory system's impact on blood pH
• Analyze how kidneys affect acid-base balance

Importance of Acid-Base Balance

• Essential for physiological functioning
• Measured by pH scale
• Buffers prevent drastic pH changes by neutralizing excess acids/bases

Buffer Systems in the Body

• Chemical Buffers: Quickly adjust pH in seconds
• Respiratory System: Adjusts blood pH in minutes by exhaling CO2
• Renal System: Adjusts blood pH over hours/days by excreting H+ and conserving bicarbonate

Main Buffer Systems

• Plasma Proteins, Phosphate, Bicarbonate, and Carbonic Acid Buffers
• Kidneys maintain plasma pH by excreting hydrogen ions and generating bicarbonate
• Protein buffers work primarily inside cells

Protein Buffers

• Proteins act as buffers due to charged amino and carboxyl groups
• Accounts for significant buffering power in blood and cells

Hemoglobin as a Buffer

• Buffers hydrogen ions during CO2 conversion to bicarbonate
• Reversed in pulmonary capillaries for CO2 exhalation

Phosphate Buffer

• Consists of sodium dihydrogen phosphate and sodium monohydrogen phosphate
• Reacts with strong acids/bases to form weak acids/bases and salts

Bicarbonate-Carbonic Acid Buffer

• Functions similarly to phosphate buffer
• Maintains a 20:1 ratio in blood to manage acidity
• Regulated by CO2 expiration in lungs and bicarbonate conservation in kidneys

Respiratory Regulation

• Balances acid-base by controlling carbonic acid levels
• CO2 forms carbonic acid in blood; exhalation decreases acidity
• Changes in breathing rate affect pH
• Chemoreceptors adjust breathing based on CO2 levels

Renal Regulation

• Controls blood bicarbonate levels
• Steps for bicarbonate conservation in the renal system:
  1. Sodium ions reabsorbed; hydrogen ions expelled
  2. Bicarbonate converted to CO2 and water in filtrate
  3. CO2 into renal cells, converted back to bicarbonate
  4. Released bicarbonate into blood

Disorders: Ketoacidosis

• Occurs in diabetes due to fatty acid breakdown
• Symptoms include deep breathing, fruity breath, dry skin, and nausea
• Treated with insulin and sugar intake

Review

• Body uses buffers to maintain pH between 7.35 and 7.45
• Primary substances: cell/plasma proteins, hemoglobin, phosphates, bicarbonate ions, and carbonic acid
• Respiratory and renal systems are key in removing excess CO2 and H+

Glossary

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

Critical Thinking Questions

1. Explain bicarbonate conservation in the renal system.
2. Describe how the respiratory system manages carbonic acid levels in the blood.

Source: Anatomy & Physiology by OpenStax, licensed under CC BY-SA. Access for free at OpenStax.