How stress affects the endocrine system

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David McQuillan (2008). Otago Polytechnic


The hormonal cascade of the fight or flight response which is the emotional aspect of the stress reponse propogates through three main steps

  1. Stimulation of the hypothalamus by the amygdala causes the release of corticotrophin-releasing factor (CRF).
  2. CRF then stimulates the pituitary gland causing release of adrenocorticotrophin (ACTH) into the bloodstream
  3. ACTH travels through the bloodstream and stimulates the adrenal glands causing the release of ephinephrine (adrenaline) and glucocorticoids including cortisol.


The effects of ephinephrine (adrenaline)

  • Dilates pupils
  • Increases heart rate, stroke volume and bp (blood flow may actually increase 300-400% in some cases)
  • Constricts arterioles which serve the internal organs and the skin
  • Dilates arterioles which serve the legs & arms
  • Stimulates release of glucose from body stores through two pathways
    • Glycolysis splits glycogen stores to release glucose into the bloodstream
    • Fat metabolism is increased which also releases glucose into the bloodstream
  • Suppresses immune system
  • Increases breathing rate


The effects of cortisol and other glucocorticoids

  • Increase blood pressure
  • Stimulate release of glucose from body stores through three pathways
    • Glycolysis splits glycogen stores to release glucose into the bloodstream
    • Fat metabolism is increased which also releases glucose into the bloodstream
    • Protein is broken down
  • Inhibits converstion of glucose into glycogen (glycogenesis)
  • Anti-inflammatory effects
  • Slows down healing
  • Suppresses immune system
  • Inhibits secretion of CRH (creating a negative feedback cycle)
  • Inhibits bone formation


Involvement of other biochemicals (Klein, 2004)

New research is proving the involvement many other biochemicals in the stress response

  • Cytokines
  • Vasopressin
  • Vasoactive intestinal polypeptide
  • Neuropeptide Y
  • Substance P
  • Serotonin
  • Dopamine
  • Nitric oxide
  • Cholecysokinin
  • Estrogen & progesterone
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