Acid-base map and compensatory mechanisms

Summary

This script explains the complex balance of pH in the human body, focusing on how biochemical reactions are regulated by enzymes that depend on precise pH levels. The pH balance is controlled by the ratio of bicarbonate and carbon dioxide, illustrated through the Henderson-Hasselbalch equation. It introduces the acid-base map to show how pH changes based on bicarbonate and CO2 levels, highlighting conditions like acidosis and alkalosis. The script also discusses the body’s mechanisms, involving the lungs and kidneys, to regulate pH and the concept of respiratory and metabolic compensations.

Takeaways

• 🧬 Biochemical reactions in the body are mediated by enzymes, which require a tightly regulated pH to function properly.
• ⚖️ The pH of body fluids is determined by the ratio of bicarbonate (HCO3-) to carbon dioxide (CO2), calculated by the Henderson-Hasselbalch equation.
• 📉 The acid-base map uses bicarbonate concentration on the x-axis and partial pressure of CO2 (PCO2) on the y-axis to visualize pH changes.
• 🔗 Isohydric lines represent constant pH values, showing various combinations of bicarbonate and CO2 that result in the same pH.
• 🫁 The lungs regulate pH by adjusting CO2 through breathing, while the kidneys control bicarbonate excretion to maintain balance.
• ⬇️ Acidosis occurs when pH drops below 7.35, due to an imbalance in the ratio of bicarbonate and CO2, and can be either respiratory or metabolic.
• ⬆️ Alkalosis occurs when pH rises above 7.45, also due to imbalances, and can be respiratory or metabolic.
• 🚶‍♂️ Respiratory acidosis is caused by CO2 retention (e.g., from shallow breathing), while metabolic acidosis is due to bicarbonate loss (e.g., from diarrhea).
• 🏃‍♀️ Respiratory alkalosis involves excessive CO2 loss (e.g., hyperventilation), while metabolic alkalosis results from excessive bicarbonate retention.
• 💡 Mixed acid-base disorders involve multiple disturbances, such as simultaneous acidosis and alkalosis, leading to complex pH changes.

Q & A

What is the significance of the pH level in our body fluids?

The pH level in our body fluids is crucial because it determines the environment in which biochemical reactions occur, mediated by enzymes. These reactions need a tightly regulated pH range to function properly.

How is the pH of our body fluids regulated?

The pH of our body fluids is regulated by the balance between bicarbonate (bases) and carbon dioxide (acids), and is calculated using the Henderson-Hasselbalch equation.

What is the Henderson-Hasselbalch equation?

The Henderson-Hasselbalch equation is a formula used to calculate the pH of blood plasma, expressed as pH = 6.1 + log([HCO3-]/(0.03 * pCO2)), where [HCO3-] is the bicarbonate concentration and pCO2 is the partial pressure of carbon dioxide.

What is an isohydric line on an acid-base map?

An isohydric line on an acid-base map is a line that represents points of equal pH, plotted using the Henderson-Hasselbalch equation, with bicarbonate concentration on the x-axis and partial pressure of carbon dioxide (pCO2) on the y-axis.

What is the normal physiologic pH range for arterial blood?

The normal physiologic pH range for arterial blood is between 7.35 and 7.45.

How do the lungs help maintain acid-base balance?

The lungs help maintain acid-base balance by controlling the rate and depth of breathing, which regulates the amount of carbon dioxide exhaled.

What role do the kidneys play in acid-base homeostasis?

The kidneys play a role in acid-base homeostasis by controlling the amount of bicarbonate excreted, thus helping to maintain the pH balance.

What is acidosis and how does it manifest on the acid-base map?

Acidosis is a condition where the pH drops below 7.35 due to a decrease in bicarbonate concentration or increase in carbon dioxide levels. On the acid-base map, it is represented by points in the upper left part of the map.

What is alkalosis and how does it appear on the acid-base map?

Alkalosis is a condition where the pH rises above 7.45 due to an increase in bicarbonate concentration or decrease in carbon dioxide levels. On the acid-base map, it is represented by points in the lower right part of the map.

How does respiratory acidosis differ from metabolic acidosis?

Respiratory acidosis results from issues with the respiratory system, affecting the partial pressure of carbon dioxide, while metabolic acidosis is caused by abnormalities in bicarbonate concentration.

What are mixed acid-base disorders and how do they appear on the acid-base map?

Mixed acid-base disorders occur when there are simultaneous acidosis and alkalosis disturbances that either neutralize each other or compound to create a more severe pH disturbance. They appear in between the shaded areas of the acid-base map.