The fight or flight response

The fight or flight response

1. enables us to react quickly to life-threatening situattions

2. The amygdala & hypothalamus

   • stress response triggered by amygdala an area of the brain which associates sensory inputs (sights, sounds & smells) with emotions like fear & anger
   • the amygdala sends a distress signal to the hypothalamus

3. Response to acute (sudden) stressors

   • hypothalamus activates acute response via sympathetic nervous system (SNS)
   • SNS sends signals to adrenal medulla
   • adrenal medulla releases adrenaline into blood stream
   • Adrenaline = increase in heart rate, breathing & blood pressure so more oxygen reaches heart & muscles
   • Adrenaline also = triggers release of glucose into blood to supply energy but inhibits digestion during emergency
   • When threat has passed, parasympathetic nervous system restores heart rate & blood pressure to normal & restarts normal digestion

4. Response to chronic (ongoing) stressors

   • threat is ongoing so HPA axis kicks in
   • H - hypothalamus releases cortico-tropin releasing hormone (CRH) into blood stream
   • P - pituitary gland responds to CRH & releases Adrenal-cortico-tropic hormone (ACTH)
   • A - Adrenal cortex is stimulated by ACTH & releases cortisol
   • Cortisol
     • reduces sensitivity to pain
     • gives quick burst of energy
     • cortisol has negative feedback effect on hypothalamus & pituitary

5. Evaluation

   • Negative effects on body
     • Long term increase in blood pressure can lead to damage to the blood vessels & heart disease
     • & too much cortisol surpresses immune response
     • increases likelihood of becoming ill
   • 'tend & befriend' response more characteristic copping pattern for females (Taylor et al)
     • women's stress response evolved to enable them to be the primary caregiver of children, fight or flight response would danger children
     • difference could be linked to the release of the hormone oxytocin in caregivers, which decreases anxiety & reduces fight or flight response
     • means may be a genetic basis to sex differences in responses to stress
   • most animals & humans'freeze' initially in response to stress ( Gray)
     • enables them to asses threat before responding
     • adrenaline & cortisol promote this hyper vigilant state, individual is alert to danger, focusing on attention on relevant sensory inputs
     • gives adaptive advantages, as we are able to choose the best response to particular threat
   • Male aggressive responses
     • There is evidence of genetic basis for gender differences in response
     • Lee & Harley found that SRY gene, found on the male Y chromosome, promotes development of male aggression
     • might prime males to release more adrenaline when threatened
     • further support for different response of females who do not have Y chromosome
   • Cooperative behaviour under stress
     • Von Dawans et al challenged the fight or flight response observing that people often cooperate during crises like the 9/11 terrorist attacks in new york
     • acute stress can increase friendly behaviour even in men
     • humans social, mutually protective behaviour as contributed to our success as a species
     • human behaviour in response to stress may depend on social/cultural factors not just biologically determined responses