Hypothalamus and Pituitary Gland Functions and Interactions

Introduction

• Hypothalamus and Pituitary Gland: Critical for hormone production and release.
• Focus: Structure, communication, and the hormonal stress response (HPA axis).

Hypothalamus

• Location: Deep in the brain, below the thalamus.
• Functions:
  • Regulation of thirst, hunger, body temperature, stress responses, reproductive behaviors, sleep-wake cycles, etc.
  • Maintains homeostasis by influencing behavioral, autonomic nervous, and neuroendocrine systems.
• Structure:
  • Over a dozen nuclei with different functions.
  • Anatomical Subdivisions:
    • Preoptic Area: Regulates body temperature, electrolyte balance, circadian rhythms, sexual behavior.
    • Tubal Hypothalamus: Involved in hunger, feeding, sexual behavior, aggressiveness, and endocrine responses.
    • Posterior Region: Involved in wakefulness, stress responses, memory.

Pituitary Gland

• Description: Endocrine gland known as the "master gland".
• Components:
  • Anterior Pituitary (Adenohypophysis):
    • Produces hormones: ACTH, TSH, LH, FSH, GH, prolactin.
    • Hormone release controlled by hypothalamus through releasing/inhibiting hormones.
    • Connected to hypothalamus via the hypothalamic-pituitary portal system.
  • Posterior Pituitary (Neurohypophysis):
    • Secretes oxytocin and vasopressin.
    • Hormones made in the hypothalamus and transported to posterior pituitary.

Communication Between Hypothalamus and Pituitary

• Anterior Pituitary Regulation:
  • Uses hypothalamic releasing and inhibiting hormones.
  • Hypothalamic-pituitary portal system delivers these hormones.
• Posterior Pituitary Regulation:
  • Hormones synthesized in hypothalamus and transported to posterior pituitary axon terminals.
  • Released by action potentials.

HPA Axis: Hormonal Stress Response

• Components: Hypothalamus, Pituitary Gland, Adrenal Glands.
• Function: Regulates body’s stress response.
• Process:
  • Hypothalamus releases corticotropin-releasing hormone (CRH).
  • CRH stimulates pituitary to release adrenocorticotropic hormone (ACTH).
  • ACTH signals adrenal glands to release cortisol.
  • Cortisol mobilizes energy and is involved in negative feedback to shut off response.