Homeostasis Lecture Notes

Introduction

• Homeostasis: The state of balance within body systems.
• Importance: Maintaining equilibrium in physiological processes.
• Mechanisms: Primarily through negative and positive feedback.

Negative Feedback Mechanism

• Definition: Counteracts changes to maintain balance.

• Example 1: Blood Glucose Regulation

  • High Glucose Levels
    • Stimulus: High blood glucose.
    • Receptor: GLUT receptors on pancreatic alpha cells.
    • Control Center: Pancreas.
    • Effector: Insulin released by pancreas, acts on body cells.
    • Response: Glucose uptake by cells, lowering blood glucose.
  • Low Glucose Levels
    • Stimulus: Low blood glucose.
    • Receptor: GLUT receptors on pancreas.
    • Control Center: Pancreas.
    • Effector: Glucagon released by pancreas, acts on liver.
    • Response: Glycogenolysis and gluconeogenesis in liver, increasing blood glucose.

• Example 2: Body Temperature Regulation

  • Cold Exposure
    • Stimulus: Cold temperature.
    • Receptors: Thermoreceptors in skin.
    • Control Center: Hypothalamus.
    • Effectors: Blood vessels, sweat glands, and muscles.
    • Responses:
      • Vasoconstriction to reduce heat loss.
      • Inhibition of sweat production.
      • Shivering to generate heat.
  • Hot Exposure
    • Stimulus: Hot temperature.
    • Receptors: Thermoreceptors in skin.
    • Control Center: Hypothalamus.
    • Effectors: Blood vessels, sweat glands, and muscles.
    • Responses:
      • Vasodilation to increase heat loss.
      • Increased sweat production for evaporative cooling.
      • Inhibition of shivering to reduce heat production.

Positive Feedback Mechanism

• Definition: Amplifies initial stimulus rather than counteracting.

• Example 1: Childbirth

  • Stimulus: Stretching of cervix by baby.
  • Receptors: Stretch receptors in uterus.
  • Control Center: Hypothalamus and posterior pituitary.
  • Effector: Oxytocin release, stimulating uterine contractions.
  • Response: Increased contractions and further cervical stretching until birth.

• Example 2: Lactation

  • Stimulus: Baby suckling on the breast.
  • Receptors: Mechanoreceptors in breast.
  • Control Center: Hypothalamus, anterior, and posterior pituitary.
  • Effectors: Prolactin and oxytocin release.
  • Responses:
    • Prolactin stimulates milk production.
    • Oxytocin stimulates milk ejection.

• Example 3: Blood Clotting

  • Stimulus: Tear in blood vessel.
  • Receptors: Chemical signals from platelets.
  • Response: Platelet plug formation through platelet aggregation, amplifying clotting.

Conclusion

• Homeostasis: Critical for maintaining balance and function in the body.
• Feedback Mechanisms: Essential for adapting to changes and ensuring physiological stability.

Note: For further understanding, refer to detailed illustrations and notes available on the Ninja Nerd website.