Fight or Flight Response

• How the fight or flight response is triggered:

  • Threat is spotted, amygdala switches on (sensory signals are associated with emotions).
  • Distress signal is sent to the hypothalamus which triggers the sympathetic nervous system (SNS) to send the message around the body.
  • There are two different systems which can be alerted depending on the stressor (acute or chronic).
• Acute (sudden) stressor response:

  • Can be triggered by dropping a valuable object, during a fight or facing a fear.
  • Response- SNS is triggered by the hypothalamus which prepares the body for rapid action. SNS sends signal to the adrenal medulla which releases adrenaline into the bloodstream.
  • This causes physiological changes:
  • Heart rate increases so more blood is pushed to muscles and heart.
  • Breathing rate increases so more oxygen is taken in and supplied to muscles.
  • Blood sugar increases providing more energy.
  • Blood is directed to vital organs.
• When the threat from an acute stressor passes, the parasympathetic branch of the SNS slows the response by inhibiting adrenaline production- heart rate decreases meaning blood pressure also decreases.
• Chronic (on-going) stressor response:

  • Can be triggered by taking an exam, long-term abuse or sports.
  • Response- the hypothalamus activates the HPA axis (hypothalamus, pituitary gland, adrenal gland)- relies on hormone signals
• What each part of the HPA axis does during the response to chronic stressors:

  • Hypothalamus- releases CRH into the bloodstream.
  • Pituitary gland- CRH reaches this gland and is detected, allowing ACTH to be transported to adrenal glands.
  • Adrenal glands- ATCH binds to receptors on the adrenal cortex, releasing cortisol. This causes quick bursts of energy, lowers pain sensitivity, impairs cognitive function and lowers the immune response.
  • The hypothalamus and pituitary gland work in a feedback loop- they use receptors to monitor the cortisol levels, by inhibiting or producing CRH or ACTH.
• Role of adrenaline in the fight or flight response:

  Adrenaline- hormone which is released by the adrenal gland during stressful/ threatening situations. Transported via the bloodstream to organs like the heart and lungs, binds to receptors on the surface of the organs- creates physiological changes. For example, the effect of adrenaline on the heart- increases heart rate, more blood reaches muscles. Effect on the lungs- increases breathing rate, increasing oxygen intake. These physiological changes aid the response to the situation- either fleeing or confronting it.