Biological Explenations of Stress

• Biological explanation 1 - Adrenaline and acute stress

  1. Hypothalamus alerted

  2. Autonomic nervous system (ANS) aroused

  3. Sympathetic branch of ANS activated

  4. Adrenal medulla releases adrenaline and noradrenaline

  5. Circulate through body

  6. Parasympathetic branch reduces stress response
• Sympathomedullary Pathway

  • Also known as sympathetic adrenal medullary pathway (SAM)
  • Hypothalamus activates sympathetic branch of ANS
  • Adrenal Medulla releases adrenaline and noradrenaline
  • Results in increased energy, alertness, blood flow, heart and respiration rate
• Fight and flight response

  • The SAM response is also known as the Fight and Flight response
  • Changes caused by adrenaline get the body ready to fight or flight
  • Diverts blood and oxygen away from non-essential areas to muscles
  • Prepares the body to face the stressor
• An Evolutionary Response


  • The SAM response is seen as an adaptive response
  • Helped ancestors cope with threats requiring an energetic response
  • In modern times threats don't need a physical response, so it leaves the individual in a permanent state of arousal
• High level of adrenaline and noradrenaline


  Have a direct effect on the heart, linked to cardiovascular disorders, stroke, heart attacks
• Lab research on gender differences is unethical and artificial
• Gender differences


  • Men have fight or flight response, women respond in tend or befriend
  • Women don't fight or flight because of their offspring
• Biological explanation 2 - Cortisol and chronic stress

  1. Hypothalamic-pituitary-adrenal (HPA) system activated

  2. Hypothalamus produces corticotropin

  3. Pituitary gland releases adrenocorticotropin hormone (ACTH)

  4. ACTH stimulates adrenal cortex to release cortisol
• Hypothalamic Pituitary Adrenal Axis (HPA)

  • Body's response to chronic (long term) stress
  • Hypothalamus releases corticotropic-releasing factor (CRF)
  • Pituitary gland releases adrenocorticotrophic hormone (ACTH)
  • ACTH stimulates adrenal cortex to produce corticosteroids including cortisol
• Cortisol

  • Steroid hormone from the glucocorticoid family
  • Plays a role in the central nervous system, involved in learning, memory, regulates glucose storage and immune system
  • When released in response to stress, lowers sensitivity to pain and releases glucose for energy to deal with the ongoing stressor
  • Can affect cognitive performance and lower the immune system
• Cortisol administered to women

  Showed significantly reduced recall of words learned
• Chronic stress

  Immune system is seen as a non-essential response so is shut down, causing immunosuppression and colds/infections
• Hard to establish cause-and-effect relationships between stress and subsequent illness
• Low levels of cortisol can also cause health problems, such as chronic fatigue syndrome and PTSD
• It may be important to have a balanced level of cortisol without any sudden spikes or drops