Endocrine Control

Key Glands

• Hypothalamus: Part of the forebrain, receives neural signals, funnels signals to the pituitary gland.
• Pituitary Gland: Below the hypothalamus, controls other endocrine glands and hormonal responses.
  • Anterior Pituitary: Interacts with the hypothalamus via the hypophyseal portal system.
  • Posterior Pituitary: Interacts with the hypothalamus via nerve stimulation.

Hypothalamus to Anterior Pituitary

• Hypophyseal Portal System: Capillary system linking hypothalamus and pituitary.
  • Hormones are secreted into this system, acting as paracrine signals.

Hormones & Functions

• Gonadotropin-Releasing Hormone (GnRH): Stimulates release of FSH and LH, affecting gonads.
• Corticotropin-Releasing Hormone (CRH): Stimulates release of ACTH, affecting adrenal glands.
• Thyroid-Releasing Hormone (TRH): Stimulates release of TSH, affecting thyroid gland.
• Growth Hormone-Releasing Hormone: Stimulates release of growth hormone, affecting bones and muscles.
• Prolactin Inhibitory Factor (PIF): Stops prolactin release when secretion stops; affects milk production.

Tropic vs. Direct Hormones

• FLAT PEG Mnemonic:
  • FLAT (Tropic Hormones): FSH, LH, ACTH, TSH
    • Stimulate other endocrine glands.
  • PEG (Direct Hormones): Prolactin, Endorphins, Growth Hormone
    • Affect body parts directly.

Hypothalamus to Posterior Pituitary

• Communicates via nerve signals down the pituitary stalk.
• Hormones:
  • ADH (Antidiuretic Hormone): Retains water in kidneys.
  • Oxytocin: Involved in uterine contractions.

Summary

• Endocrine control is orchestrated by the pituitary gland, under the influence of the hypothalamus.
• Overall mechanism: Chemical messages facilitate stimulation between different parts of the body.