LO2

Regulation and Integration of the Body

Posterior Pituitary
  • Composition: Made of neural tissue, unlike the anterior pituitary (glandular tissue).
  • Hormones Stored:
    • Antidiuretic hormone (ADH)
    • Oxytocin (OT)
  • Function: Doesn't make hormones; it stores hormones made by the hypothalamus.
  • Origin: Nerve fibers start in the hypothalamus.
  • Storage & Release: Hypothalamic hormones are stored here and released when the nervous system signals.
Control of Pituitary Secretions
  • Release Pattern: Hormones are released in bursts, not steadily.
    • Example: Growth hormone (GH) mostly released at night.
    • Example: Luteinizing hormone (LH) peaks mid-menstrual cycle.
  • CNS Role (Central Nervous System): Helps manage hormone release.
    • Checks internal and external body conditions.
    • Releases hormones when needed (e.g., TSH when cold).
    • Triggers GH after meals for fat breakdown and tissue growth.
  • Negative Feedback Control:
    • Target organs signal back to the pituitary.
    • When the pituitary tells a gland to release a hormone, that hormone then tells the pituitary to stop releasing more, keeping levels balanced (homeostasis).
Hormones of the Pituitary Gland
  • Anterior Pituitary Hormones:
    • Growth Hormone (GH) (Somatotropin)
    • Target: Liver, bone, muscle, fat (body-wide)
    • Effect: Promotes growth and repair, breaks down protein and fat.
    • Prolactin (PRL)
    • Target: Mammary glands
    • Effect: Stimulates milk production.
    • Thyroid-Stimulating Hormone (TSH)
    • Target: Thyroid gland
    • Effect: Boosts thyroid growth and thyroid hormone release.
    • Adrenocorticotropic Hormone (ACTH)
    • Target: Adrenal cortex
    • Effect: Triggers corticosteroid release from adrenal cortex.
    • Follicle-Stimulating Hormone (FSH)
    • Target: Ovaries and testes
    • Effect: Female - starts egg production; Male - stimulates sperm production.
    • Luteinizing Hormone (LH)
    • Target: Ovaries and testes
    • Effect: Female - causes ovulation and estrogen/progesterone release; Male - stimulates testosterone release.
  • Posterior Pituitary Hormones:
    • Antidiuretic Hormone (ADH) (Vasopressin)
    • Target: Kidneys
    • Effect: Reduces urine volume, prevents dehydration.
    • Oxytocin (OT)
    • Target: Uterus and mammary glands
    • Effect: Causes uterine contractions during birth; triggers milk ejection.
Fast Facts
  • Thyroid Hormones: Control metabolism and increase body temperature.
  • Endocrinology: Study of the endocrine system and its issues.
  • Negative Feedback: Keeps hormone levels balanced, bringing them back to normal after they've done their job.
Growth Hormone (GH) Functionality
  • Main Roles: GH helps with:
    • Making proteins
    • Using fats and carbs for energy
    • Growing bones and muscles.
  • Problems with GH Levels:
    • Too Much GH (Hypersecretion):
    • Childhood: Causes gigantism (very fast growth).
    • Adulthood (after growth plates close): Leads to acromegaly (enlarged hands, feet, face).
    • Too Little GH (Hyposecretion):
    • Childhood: Causes pituitary dwarfism (stunted growth), treatable with injections.
Hormones Released by the Hypothalamus
  • These hormones either make the anterior pituitary release or stop releasing its own hormones:
    • Gonadotropin-releasing hormone (GnRH): Boosts FSH and LH release.
    • Thyrotropin-releasing hormone (TRH): Stimulates TSH release.
    • Corticotropin-releasing hormone (CRH): Encourages ACTH release.
    • Prolactin-releasing hormone (PRH): Promotes prolactin release.
    • Prolactin-inhibiting hormone (PIH): Stops prolactin release.
    • **Growth hormone-re