The Endocrine System

I. Overview

II. Hormones

A. Hormone-Target Cell Specificity

B. Mechanism of Hormone Action

  1. A hormonal stimulus typically produces one or more of the following changes:
    1. changes in plasma membrane permeability and/or electrical state (membrane potential)
    2. synthesis of proteins or certain regulatory molecules (such as enzymes) within the cell
    3. enzyme regulation (activation or deactivation)
    4. induce secretion
    5. stimulation of mitosis
  2. Two major mechanisms leading to hormone action: 
    1. Second messenger systems (mediate the target cell's response to hormone) Diagram
      • Hormone binds to a receptor on the cell membrane
      • Receptor causes adenylate cyclase in the membrane to be active and convert ATP into cAMP
      • cAMP activates protein kinases
      • Protein kinases activates enzymes, stimulate cellular secretion, opens ion channels, etc.....
    2. Direct gene activation Diagram
      • Steroid hormones diffuse easily into their target cells
      • They bind to receptors within the nucleus
      • The activated complex then interacts with the nuclear chromatin binding to a receptor protein
      • Binding to chromatin "turns on" DNA Transcription of mRNA which is used to direct the synthesis of other proteins (e.g. enzymes).

C. Control of Hormone Release

III. Endocrine Organs of the Body

A. Pituitary Gland (Hypophysis) Diagram

B. Thyroid Gland Diagram

C. Parathyroid Diagram Diagram

D. Adrenal Gland (Suprarenal) Diagram

E. Pancreas Diagram

F. Gonads

G. Pineal Gland Diagram

H. Thymus

I. Hormone Overview: Diagram

IV. Clinical Terms Diagram

Pituitary Disorders
Thyroid Disorders
Adrenal Disorders
Parathyroid Disorders
Pancreatic Disorders