Fight-or-flight response

• The fight-or-flight response is triggered by a perceived threat or stressful situation e.g. a car approaching suddenly. It causes adrenaline to be released which causes physiological changes like increased heart rate.
• A perceived stress/threat activates the sympathomedullary pathway, leading to the release of adrenaline. This leads to an increase in heart rate and breathing rate. Also, the digestive system is "shut-down" as blood flow to the digestive organs is redirected to the muscles.
• Adrenaline is released from the adrenal medulla in response to activation of the sympathomedullary pathway. It prepares the body for action - a fight-or-flight response.
• Adrenaline causes physiological changes in the body such as:

  • increase heart and breathing rate
  • increase the rate of blood flow and raise blood pressure
  • directs blood flow away from the digestive system, kidneys and the skin
  • increase blood supply to skeletal muscle for physical action
  • increases respiration
• The adrenal cortex releases cortisol, a hormone involved in the stress response. Cortisol helps regulate metabolism, blood pressure and immune responses during stress.

  • It provides the body with energy by increasing glucose availability.
• The amygdala, a part of the brain involved in emotional processing, detects a threat.

  • It sends a distress signal to the hypothalamus, which coordinates the response via the autonomic nervous system (ANS).
• Sympathomedullary Pathway (SAM) – Acute Stress (Immediate)

  • For short-term stressors (e.g., being chased).
  • Hypothalamus activates the sympathetic branch of the ANS.
  • This stimulates the adrenal medulla (in the adrenal glands) to release:
  • Adrenaline (epinephrine)
  • Noradrenaline (norepinephrine)
• Hypothalamic-Pituitary-Adrenal (HPA) Axis – Chronic Stress

  • For longer-term or ongoing stressors.
  • Hypothalamus releases CRH (corticotropin-releasing hormone).
  • This stimulates the pituitary gland to release ACTH (adrenocorticotropic hormone).
  • ACTH stimulates the adrenal cortex to release cortisol (a stress hormone).
• Effects of cortisol:

  • Maintains steady blood glucose
  • Suppresses immune system
  • Increases energy availability
• One strength of the fight-or-flight response is that it is supported by strong biological and scientific evidence. The model is based on clear, measurable physiological mechanisms involving the autonomic nervous system (ANS) and the endocrine system. These processes can be observed and measured through indicators such as increased heart rate, blood pressure, or cortisol levels in the blood or saliva. This gives the model high scientific validity and supports the idea that it reflects genuine, universal aspects of the human stress response.
• A limitation of the fight-or-flight response is that it may be outdated in modern life. The model evolved to deal with physical threats in early human environments, such as predatory animals or hostile individuals, but today, many of the stressors we face are psychological and long-term, e.g. exam stress, family issues. The physiological changes associated with the stress response, such as increased blood pressure and suppressed digestion, are not helpful for these modern stressors and can even become harmful if prolonged. For instance, extended activation of the HPA axis and the continuous release of cortisol have been linked to health problems like hypertension. Therefore, the fight-or-flight model may no longer serve as a useful response to modern stressors.
• Another limitation of the fight-or-flight model is that it may suffer from gender bias, as it was largely developed based on research involving males. Taylor et al. (2000) argued that the fight-or-flight response does not fully explain how females respond to stress. Instead, women may adopt a “tend and befriend” strategy, tending to their offspring and seeking social support from others, rather than fighting or fleeing. This alternative response is thought to be biologically driven by the hormone oxytocin, which promotes bonding and calming behaviour. The effects of oxytocin are enhanced by oestrogen, which is more prevalent in females, supporting the idea that women may experience different stress responses. The original fight-or-flight model has focused mostly on male animals or male participants, so it may be androcentric. Therefore, reducing the universality of the fight-or-flight response.
• The fight-or-flight model has also been criticised for being too simplistic, as it overlooks other possible behavioural responses to threat. Jeffrey Gray (1988) proposed the addition of a third response: “freeze", where an individual becomes hypervigilant, motionless, and focused on assessing the threat before deciding the most effective response. The freeze response can be highly adaptive, as it can help avoid detection by predators and allows for better risk evaluation, allowing a safer reaction, promoting survival. This weakens the original model as it is reductionist, ignoring the complex range of possible behavioural responses to threats, reducing its explanatory power.