Acid Base Physiology | Part One | Basics | Buffers | Renal Physiology

Summary

This video explains the buffer system in acid-base physiology, focusing on how the body maintains the balance of hydrogen ions in the blood. It covers key concepts like acids, bases, pH, and the relationship between pH and hydrogen ion concentration. The video discusses the main buffer systems, including the bicarbonate-carbon dioxide buffer, phosphate buffer, and protein buffers like hemoglobin. It also delves into the roles of the lungs and kidneys in regulating acid-base balance, highlighting their interactions with buffers to manage pH levels and maintain homeostasis in the body.

Takeaways

• 😀 Acids are substances that donate hydrogen ions (H+), while bases accept them. Examples include hydrochloric acid (strong acid) and bicarbonate (weak base).
• 😀 The concentration of hydrogen ions in the blood is very low, around 40 nan equivalents per liter, and is measured by pH, which is inversely related to hydrogen ion concentration.
• 😀 A pH of 7.4 is considered normal for blood, with a range of 7.37 to 7.42, indicating a balance of acids and bases in the body.
• 😀 Acidemia occurs when the pH is less than 7.4 (higher hydrogen ion concentration), while alkalemia happens when the pH is above 7.4 (lower hydrogen ion concentration).
• 😀 The body produces two types of acids: volatile (carbonic acid, formed by CO2 and water) and fixed (like sulfuric acid, formed from protein metabolism).
• 😀 The lungs regulate volatile acids (carbonic acid) by exhaling CO2, while fixed acids are buffered and excreted by the kidneys.
• 😀 The three main mechanisms for acid-base regulation in the body are chemical buffers, the lungs, and the kidneys, with buffers acting fastest (within seconds to minutes).
• 😀 A buffer is a mixture of a weak acid and its conjugate base, or a weak base and its conjugate acid, which resists changes in pH.
• 😀 The Henderson-Hasselbach equation (pH = pK + log(base/acid)) helps to calculate pH based on the ratio of base to acid in a buffer system.
• 😀 The bicarbonate buffer system is the most important in the extracellular fluid, where CO2 reacts with water to form carbonic acid, which dissociates into hydrogen ions and bicarbonate.
• 😀 Phosphate buffers, mainly in the kidneys and intracellular spaces, also play a role in maintaining pH, while protein buffers, like hemoglobin, are critical intracellular buffers.

Q & A

What is the primary focus of acid-base physiology in the human body?

The primary focus of acid-base physiology in the human body is the regulation of hydrogen ions (H⁺), which determines the pH of the blood and tissues.

What is the difference between an acid and a base in terms of hydrogen ion donation?

An acid donates hydrogen ions (H⁺), while a base accepts hydrogen ions.

Can you provide examples of strong and weak acids and bases in the human body?

Strong acids in the body include hydrochloric acid (HCl), while weak acids include carbonic acid. For bases, sodium hydroxide is a strong base, while bicarbonate is a weak base.

Why is the hydrogen ion concentration expressed as pH, and what does it represent?

The hydrogen ion concentration is expressed as pH because it is easier to manage very small concentrations. pH is the logarithmic inverse of the hydrogen ion concentration, and it reflects the acidity or alkalinity of a solution.

What is the normal pH range of blood, and how is it related to hydrogen ion concentration?

The normal pH of blood is between 7.37 and 7.42. When the hydrogen ion concentration increases, the pH decreases (acidemia), and when the concentration decreases, the pH increases (alkalemia).

What is the distinction between volatile and fixed acids in the body?

Volatile acids, like carbonic acid, are produced from CO₂ and can be exhaled through the lungs. Fixed acids, like sulfuric and phosphoric acid, are produced from protein and phospholipid metabolism and must be excreted by the kidneys.

How do buffers help regulate pH in the body?

Buffers resist changes in pH by binding to excess hydrogen ions when the concentration is high, or releasing hydrogen ions when the concentration is low, maintaining a stable pH in the body.

What is the Henderson-Hasselbalch equation, and what does it describe?

The Henderson-Hasselbalch equation, pH = pK + log(base/acid), describes the relationship between pH, the pK (dissociation constant), and the ratio of base to acid in a buffer system.

What role does bicarbonate play in the bicarbonate-carbonic acid buffer system?

Bicarbonate acts as the base in the bicarbonate-carbonic acid buffer system. It helps neutralize excess hydrogen ions by binding to them, while carbonic acid (derived from CO₂) is the acidic component that dissociates to release hydrogen ions when necessary.

What are the main buffer systems in the body, and where do they function?

The main buffer systems are the bicarbonate-carbonic acid buffer (extracellular), phosphate buffer (urinary and intracellular), and protein buffers (intracellular, particularly hemoglobin). These systems work together to maintain a stable pH in various body compartments.

How do the kidneys and lungs collaborate in acid-base regulation?

The kidneys excrete fixed acids and regulate bicarbonate levels, while the lungs adjust CO₂ levels, which in turn affects the bicarbonate-carbonic acid buffer system. This coordination helps maintain the body’s pH within a narrow range.