Epinephrine

Summary

Epinephrine is a hormone that is produced by the adrenal medulla. Epinephrine is a tyrosine-derivative that is hydrophilic, and can therefore easily dissolve in water and blood to move throughout the body. Once epinephrine reaches a target cell, it relies on external receptors outside of the cell to trigger a second messenger cascade inside the cell, in order to cause epinephrine’s downstream effects. Epinephrine is produced when we are stressed, and stimulates the fight-or-flight response. During this response, epinephrine increases blood flow to skeletal muscles and reduces blood flow to digestive organs or other organs not necessary for survival.

Key Points

• Epinephrine
  • Norepinephrine has the same endocrine function as Epinephrine
  • Origin: Adrenal Medulla
  • Type: Tyrosine derivative
    • Water-soluble (hydrophilic)
      • Cannot diffuse across cell membrane
      • Uses GPCR pathway
        • Uses a secondary messenger system because Epinephrine acts like a hydrophilic protein hormone
  • Trigger: Stress
  • Effects:
    • Increases blood flow to skeletal muscles
    • Constricts blood vessels/reduces blood flow to most organs
    • Promotes glycogenolysis in liver
    • All actions by epinephrine are designed to promote the fight or flight response