Fight or Flight

• What is a stress?

  caused by a mismatch of the perceived demands of a situation and your perceived ability to cope.
• What is a stressor?

  any event, experience or environmental stimulus that causes stress.
• When is it helpful?

  - being attacked by something or someone -> self defence.

  - running away from a fire.

  - anything life threatening.
• Response to acute (sudden) stressors - SAM

  sympathetic-adrenal medullary system

  Sympathetic Nervous System

  - when SNS is triggered, process prepares body for action.

  - sends a signal to adrenal medulla - adrenaline released into bloodstream.

  Adrenaline

  - heart beats faster, pushing blood to muscles, heart and other vital organs and blood pressure increases.

  - breathing becomes rapid to take in oxygen.

  Parasympathetic Nervous System

  - dampens down stress response once threat has passed.

  - slow down the heart and reduce blood pressure.

  - digestion begins again.
• Response to Chronic (ongoing) stressors - HPA

  hypothalamus-pituitary adrenal axis

  - if threat continues, a second system kicks in.

  'H' hypothalamus

  - in response to continued threat, hypothalamus releases, CRH, which is released into bloodstream in response to stressor.

  'P' pituitary gland

  - CRH causes pituitary to produce and release ACTH.

  - ACTH is transported in bloodstream to its target site in adrenal glands.

  'A' adrenal gland

  - ACTH stimulates adrenal cortex to release hormones, including cortisol.

  - cortisol - important in response.
• HPA


  hypothalamus -> pituitary gland -> ACTH -> adrenal cortex -> glucocorticoids -> increases body's energy level.

  - adrenal gland stimulate pituitary gland.

  - in response to stressor, pituitary gland is directed by hypothalamus to release ACTH.

  - ACTH stimulates adrenal cortex to secrete glucocorticoids to help increase body's energy level.
• SAM


  hypothalamus -> sympathetic branch -> adrenal medulla

  either: adrenaline -> constricts blood vessels, increases heart rate OR noradrenaline -> increase in blood sugar.

  - adrenal gland stimulates sympathetic branch of ANS.

  - directed by hypothalamus, sympathetic branch sends messages via neurotransmitters.

  - adrenal medulla secretes adrenaline and noradrenaline.
• Weakness - 'tend or befriend' response

  fight or flight has been criticised because females may display a different pattern to males.

  involves protecting themselves and their young through nurturing behaviours and forming protective alliances with other women.

  may have a different system to coping with stress as their responses evolved in the context of being primary caregiver of their children.

  studies with rats shows that there might be a physiological response to stress, inhibiting release of oxytocin.
• Weakness - negative consequences of fight or flight response

  stressors of modern life don't generally need a physical reaction that gives us energy to fight or flight.

  modern humans arises when stress responses is repeatedly activated e.g. increased blood pressure that's characteristics of SNS activation can lead to physical damage in blood vessels.

  cortisol may assist body in fighting a viral infection of healing damaged tissue, too much it suppresses the immune response.
• Strength - fight or flight doesn't tell the whole story

  Gray argues that the first phase of reaction to a threat isn't to fight or flee, but avoid confrontation.

  prior to responding with attacking or running away, most animals typically display the 'freeze' response.

  adaptive advantages of this for humans is that 'freezing' focuses attention and makes them look for new info to make the best response for particular threat.
• Weakness - a genetic basis to sex differences in fight of flight

  Lee and Harley have found evidence of a genetic basis for gender differences in fight or flight response.

  SRY gene - exclusively on Y chromosome, promotes aggression and resulting in fight or flight response to stress.

  SRY gene may prime males to respond in this way by release of hormones like adrenaline.

  absence of SRY gene in females together with the actions of oestrogen and oxytocin, may prevent stress response.