Lecture on Homeostasis

Introduction to Change and Consistency

• Personal change is constant over time.
• Body requires consistency in internal conditions for health.
• Blood pressure, calcium levels, and sugar levels must be maintained.
  • Low blood pressure: risk of fainting.
  • High blood pressure: risk of heart issues.
  • Low calcium: weaker bones.
  • High sugar: blood vessel damage.

Homeostasis

• Definition: process by which the body maintains stable internal conditions.
• Example metaphor: balancing a ruler.

Steps of Homeostasis

1. Set Point
   • Ideal internal condition (e.g., 120/80 blood pressure).
   • Ruler analogy: ideal position is straight up.
   • Real condition rarely at set point, always correcting.
2. Detection (Sensing)
   • Use sensory inputs (e.g., sight, touch) to detect imbalance.
   • Must sense an issue to address it.
3. Integration
   • Brain compares current condition to set point.
   • Subconscious process.
4. Effector Response
   • Action taken to correct the condition.
   • E.g., moving the hand to balance the ruler.

Negative Feedback Loop

• Definition: process where a change leads to an opposite response to maintain equilibrium.
• Example: correcting direction of ruler balance.
• Always aims to bring variables back to set point.

Example 1: Blood Pressure Regulation

• Set Point: 120/80 mmHg.
• High Blood Pressure:
  • Detected by stretch receptors in aorta and carotid artery.
  • Medulla integrates data and sends signals.
  • Effectors: Heart rate slows, blood vessels dilate.
• Low Blood Pressure:
  • Same sensing and integration as high blood pressure.
  • Effectors: Heart rate increases, blood vessels constrict.
• Both increase and decrease processes are negative feedback loops.

Example 2: Body Temperature Regulation

• Set Point: 37°C (98.6°F).
• High Temperature:
  • Detected by nerve cells in brain/skin.
  • Hypothalamus integrates data.
  • Effectors: Sweat release, blood vessel dilation.
• Low Temperature:
  • Same sensing and integration.
  • Effectors: Shivering, blood vessel constriction.

Recap

• All internal conditions use homeostatic negative feedback loops.
• Steps: Set Point, Sensing, Integration, Effector Response.
• Control center often the brain.

Additional Resources

• Practice with homeostasis feedback loop cards for mastery.