Homeostasis Lecture Notes

Introduction

• Homeostasis: The maintenance of a state of balance within body systems; maintaining equilibrium.
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Understanding Homeostasis

• Homeostasis involves maintaining a balance (e.g., glucose levels).
• Imbalance counteracted through negative feedback mechanisms.

Negative Feedback Mechanisms

Glucose Regulation

• High Glucose Levels:

  • Stimulus: High blood glucose.
  • Receptors: Pancreatic alpha cells with GLUT receptors.
  • Control Center: Pancreas, releasing insulin.
  • Effector: Body cells that take in glucose.
  • Response: Lower blood glucose by shuttling glucose into cells.

• Low Glucose Levels:

  • Stimulus: Low blood glucose.
  • Receptors: GLUT receptors on pancreas.
  • Control Center: Pancreas, releasing glucagon.
  • Effector: Liver, releasing glucose.
  • Response: Increase blood glucose via glycogenolysis and gluconeogenesis.

Temperature Regulation

• Cold Temperatures:

  • Stimulus: Cold environment.
  • Receptors: Thermoreceptors in skin.
  • Control Center: Hypothalamus.
  • Effectors:
    • Blood vessels (vasoconstriction).
    • Muscles (shivering).
  • Response: Increase heat production, reduce cooling.

• Hot Temperatures:

  • Stimulus: Hot environment.
  • Receptors: Thermoreceptors.
  • Control Center: Hypothalamus.
  • Effectors:
    • Blood vessels (vasodilation).
    • Sweat glands (increased sweating).
  • Response: Enhance cooling, reduce body temperature.

Positive Feedback Mechanisms

Birthing Process

• Stimulus: Cervix stretch by baby.
• Receptors: Stretch receptors in uterus.
• Control Center: Hypothalamus and posterior pituitary.
• Effector: Uterus (oxytocin induced contractions).
• Response: Amplified uterine contractions until birth.

Lactation

• Stimulus: Baby suckling.
• Receptors: Mechanoreceptors in breast.
• Control Center: Hypothalamus, anterior/posterior pituitary.
• Effectors:
  • Prolactin: Stimulates milk production.
  • Oxytocin: Stimulates milk ejection.
• Response: Continuation of milk production and ejection.

Blood Clotting

• Stimulus: Blood vessel injury.
• Receptors: Platelets' receptors detect injury.
• Response: Platelet aggregation and chemical release to recruit more platelets, forming a platelet plug.
• Amplification of platelet recruitment to seal wound.

Conclusion

• Negative Feedback: Balances high/low levels (e.g., temperature, glucose).
• Positive Feedback: Amplifies process (e.g., childbirth, lactation, blood clotting).
• Understanding homeostasis is crucial for recognizing body balance and disease mechanisms.