JC HBHD 2 Week 2 Chapter 22 Acid-Base Balance

Acid-Base Balance

• Acid-base balance is the coordinated homeostatic mechanisms that regulate the normal pH of body fluids. This prevents swings in pH when excess acids or bases are present.
• The pH scale measures the relative hydrogen ion (H+) concentration in a fluid. A pH of 7.0 is neutral, higher than 7.0 is alkaline, and less than 7.0 is acidic.
• The normal range of blood pH is approximately 7.35 to 7.45. Arterial blood pH is about 7.45, while venous blood pH is about 7.35.
• The pH scale is based on multiples of 10, with each pH unit representing a tenfold change in H+ concentration. Large pH fluctuations can seem small on the scale.
• Excess acids, such as carbonic acid, formed in the blood are removed by the lungs by eliminating carbon dioxide.
• Three chemical mechanisms control pH: chemical/buffer mechanisms, respiratory mechanisms, and urinary mechanisms.
• Buffers are substances that prevent drastic pH changes when an acid or base is added to a fluid. "Fixed" acids are primarily buffered by sodium bicarbonate (NaHCO₃).
• Buffer pairs, such as sodium bicarbonate (NaHCO₃) and carbonic acid (H₂CO₃), work together to regulate pH. The ratio of NaHCO₃ to H₂CO₃ is typically 20:1.
• Respiratory mechanisms control pH by regulating the amount of CO2 in the blood. The respiratory control centers in the brainstem adjust respiration rate to decrease or increase CO₂ levels. Lowering CO₂ decreases carbonic acid and increases blood pH.
• The urinary mechanisms control pH by the secretion of hydrogen (H+) ions and ammonia (NH₃) into the urine. Exchanging these ions for NaHCO₃ that is reabsorbed into the blood.
• Acidosis and alkalosis are two types of pH imbalances. Disturbances in acid-base balance depend on the relative quantities of NaHCO₃ and H₂CO₃ in the blood.
• The body regulates both NaHCO₃ and H₂CO₃. Blood levels of NaHCO₃ are regulated by the kidneys, and H₂CO₃ levels are primarily controlled by the lungs.
• Metabolic and respiratory disturbances can alter the normal 20:1 ratio of NaHCO₃ to H₂CO₃ in the blood. These disturbances affect the levels of these key components in the body.