fight or flight

• Often the endocrine system and the autonomic nervous system (ANS) work in parallel with one another, for instance during a stressful event triggering your fight or flight response
• The hypothalamus activates the pituitary gland and this triggers activity in the sympathetic branch of the autonomic nervous system
• The ANS changes from its normal resting state (the parasympathetic state) to the physiologically aroused sympathetic state
• The stress hormone adrenaline is released from the adrenal medulla into the bloodstream
• Adrenaline triggers physiological changes in the body (e.g. increased heart rate) which creates the physiological arousal necessary for the fight or flight response
• Immediate and automatic

  • All of this happens in an instant as soon as the threat is detected
  • This is an acute response and an automatic reaction in the body
• Once the threat has passed, the parasympathetic nervous system returns the body to its resting state
• The parasympathetic branch of the ANS works in opposition to the sympathetic nervous system - its actions are antagonistic to the sympathetic system
• Rest and digest response

  The parasympathetic system acts as a 'brake' and reduces the activities of the body that were increased by the actions of the sympathetic branch
• Biological changes associated with the sympathetic state

  • Increases heart and breathing rate
  • Dilates pupils
  • Inhibits digestion and saliva production
  • Contracts rectum
• Biological changes associated with the parasympathetic state

  • Decreases heart and breathing rate
  • Constricts pupils
  • Stimulates digestion and saliva production
  • Relaxes rectum