14.01 Overview: Homeostasis

1. Definition of Homeostasis

• Homeostasis: The maintenance of a relatively constant internal environment in the body.
• Purpose: Ensures optimal conditions for cellular function despite external changes.
• Mechanism: Controlled via negative feedback to regulate various physiological parameters.

2. Homeostatic Control Systems

• Control Systems: Organisms, especially mammals, use control systems to maintain stable internal conditions.
• Sensory Cells: Detect changes in internal and external environments and relay this information to the brain.

3. Key Physiological Factors Controlled in Mammalian Homeostasis

1. Core Body Temperature
   • Maintains enzymatic activity and metabolic rates.
   • Optimal range: around 37°C in humans.
2. Metabolic Wastes (CO₂ and Urea)
   • CO₂ levels affect blood pH; excess CO₂ leads to acidosis.
   • Urea, a waste product from amino acid breakdown, is excreted to prevent toxicity.
3. Blood pH
   • Maintains a pH around 7.4.
   • Essential for protein structure and enzyme function.
4. Blood Glucose Concentration
   • Keeps glucose within an optimal range for cellular respiration.
   • Insulin and glucagon regulate glucose levels.
5. Water Potential of the Blood
   • Prevents osmotic damage to cells by regulating water balance.
   • Controlled by kidneys and ADH (antidiuretic hormone).
6. Concentrations of Respiratory Gases (O₂ and CO₂)
   • Ensures sufficient oxygen for cellular respiration.
   • Maintains low levels of CO₂ to avoid respiratory acidosis.

4. Negative Feedback in Homeostasis

• Process: Detects deviations from a set point and triggers responses to correct it.
• Example: If blood glucose rises after a meal, insulin is released to lower it back to normal.

5. Importance of Homeostasis

Cell Function: Stable internal conditions ensure cells operate efficiently, supporting life processes.

Enzyme Function: Most enzymes work within narrow temperature and pH ranges.