Negative vs Positive Feedback Loops

Introduction

• Feedback Loops: Mechanisms that help maintain homeostasis in the body.
• Homeostasis: Stability of the body's internal environment.
• Variables: Elements like body temperature, blood chemical components, etc.
• Set Points & Normal Range: Variables maintain a range where small fluctuations are okay.
• Importance of Feedback Loops: Correct imbalances in variables to maintain homeostasis.

Negative Feedback Loops

• Function: Oppose changes in variables, reduce output to bring body back to homeostasis.
• Components:
  • Receptor: Detects changes and relays information.
  • Control Center: Receives and processes information; usually the brain or endocrine glands.
  • Effector: Implements response to change; can be a cell or organ.

Working of Negative Feedback Loops

1. Stimulus: Change in variable triggers the receptor.
2. Receptor: Detects change and informs the control center.
3. Control Center: Compares current variable value to set point.
4. Effector: Acts to restore normal range by initiating physiological response.
5. Homeostasis: Effector stops once normal range is restored.

Examples

• Blood Pressure:
  • High BP: Detected by blood vessel receptors, control center (brain) signals effectors (heart/blood vessels) to decrease heart rate and increase vessel diameter.
  • Low BP: Opposite action (increase heart rate, decrease vessel size).
• Body Temperature:
  • Cold: Brain cells detect drop, signal skeletal muscles to shiver (heat production).

Positive Feedback Loops

• Function: Reinforce changes in variables, increase output.
• Characteristics:
  • Travel in the direction of variable change.
  • Quick and rapid responses, produce more product.

Example

• Labor (Childbirth):
  • Stimulus: Baby's head pushes cervix.
  • Control Center: Brain causes release of oxytocin.
  • Effector: Uterine muscles contract, reinforcing changes until birth.
  • Outcome: More oxytocin and contractions until the baby is delivered.

Conclusion

• Negative feedback loops resist changes to maintain balance.
• Positive feedback loops encourage changes for rapid adjustments.
• Both types are essential for maintaining body functions and homeostasis.