Fight or Flight Response

• Fight or Flight

  • Evolved as a survival mechanism
  • Enables us to quickly react to life-threatening situations
• Fight or Flight Process

  • When we face a threat, the amygdala is activated
  • The amygdala links sensory signals into our emotions related to fight or flight, e.g. fear, anger
  • Amygdala sends stress signal to hypothalamus
  • Hypothalamus communicates to the rest of the body.
• Response to Acute Stress (sudden stress)

  • sympathetic branch is triggered and prepares body for fight or flight
  • signals sent to the Adrenal Medulla = the release of adrenaline
• Once threat has passed...

  • return to homeostasis
  • parasympathetic branch 'dampens down' the response
• Sympathetic State


  - Increased heart rate

  - Dilated pupils

  - Increased breathing rate

  - Contracted rectum

  - Inhibited saliva production

  - Inhibited digestion
• Parasympathetic State


  - Decreased heart rate

  - Constricted pupils

  - Decreased breathing rate

  - Relaxed rectum

  - Stimulated saliva production

  - Stimulated digestion
• Response to Chronic Stress


  If something continues as a threat, the second stress response system kicks in -HPA axis.

  Consists of hypothalamus, pituitary and adrenal glands

  • Hypothalamus releases CRH (corticotrophin-releasing hormone)
  • Pituitary - CRH causes pituitary to release ACTH
  • Adrenal glands then release cortisol. This either has a positive effect (energy boost, low pain threshold) or negative (impaired cognition)