Endocrine System Lecture

Jul 13, 2024

Endocrine System Overview

What is the Endocrine System?

  • Collection of cells and glands that produce and release hormones
  • Hormones: Chemicals that enter the bloodstream to affect distant areas
  • Communication network like the nervous system, but different
    • Nervous system: Fast, direct, short-acting
    • Endocrine system: Slow, indirect, long-lasting

Main Components

Hypothalamus

  • Location: Base of the brain, below the thalamus
  • Master regulator of the endocrine system
  • Produces hormones to control other endocrine glands
    • Five Key Hormones:
      • Thyrotropin releasing hormone (TRH)
      • Corticotropin releasing hormone (CRH)
      • Growth hormone releasing hormone (GHRH)
      • Prolactin releasing hormone (PRH)
      • Gonadotropin releasing hormone (GnRH)

Structural Connections

  • Anterior Pituitary Gland: Connected by blood supply
    • Hormones travel to anterior pituitary to release separate hormones
  • Posterior Pituitary Gland: Connected by nerves
    • Direct nervous signaling for hormone release

Anterior Pituitary Gland

  • Hormones Released:
    1. Thyroid Stimulating Hormone (TSH)
    2. Adrenocorticotropic Hormone (ACTH)
    3. Growth Hormone (GH)
    4. Prolactin (PRL)
    5. Gonadotropins: Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH)

Target and Effects

  • TSH: Stimulates thyroid to release T3 (tri-iodothyronine) and T4 (thyroxine)
    • Functions: Metabolism, development, and catecholamine release
    • Calcitonin: Lowers blood calcium
  • ACTH: Stimulates adrenal cortex to release cortisol and aldosterone
    • Cortisol: Increases blood glucose, suppresses immune system, stimulates fight or flight
    • Aldosterone: Increases sodium reabsorption, raises blood pressure by increasing blood volume
  • GH: Stimulates growth, protein synthesis, metabolic activities
  • PRL: Stimulates milk production
  • LH/FSH in Gonads:
    • Females: LH stimulates progesterone and ovulation; FSH stimulates follicle maturation and estrogen production
    • Males: LH stimulates Leydig cells to produce testosterone; FSH stimulates Sertoli cells for spermatogenesis

Posterior Pituitary Gland

  • Hormones: Oxytocin and Anti-Diuretic Hormone (ADH, Vasopressin)
    • Oxytocin: Uterine contractions, milk ejection, relationship building
    • ADH: Reduces urination to maintain hydration

Thyroid Gland

  • Produces T3, T4, and Calcitonin
    • T3/T4: Key in metabolism, development, catecholamine release
    • Calcitonin: Lowers blood calcium levels

Parathyroid Gland

  • Produces Parathyroid Hormone (PTH)
    • PTH: Increases blood calcium, opposing calcitonin

Adrenal Glands

  • Consists of cortex and medulla
    • Cortex: Produces cortisol, aldosterone, androgens
    • Medulla: Produces norepinephrine and epinephrine

Pancreas

  • Both endocrine and exocrine functions
    • Endocrine Hormones: Insulin and glucagon
    • Insulin: Lowers blood glucose levels
    • Glucagon: Raises blood glucose levels

Kidneys

  • Produce renin and erythropoietin
    • Renin: Works with aldosterone to increase blood pressure
    • Erythropoietin: Stimulates red blood cell production

General Function

  • The endocrine system works to maintain homeostasis and proper physiological function through hormone release.