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Stress is a biological and psychological response experienced on encountering a threat that we feel
we do not have the resources to deal with.
A stressor is a stimulus (or threat) that causes stress e.g. exam, death of a loved one, moving house,
loss of a job.
Sudden severe stress generally produces:
Increased heart rate
Increase in breathing (lungs dilate)
Decrease in digestive activity
Liver released glucose for energy
Firstly, our body judges a situation and decides whether or not it is stressful. This decision is made
based on sensory input and processing (i.e. the things we see and hear in the situation) and also on
stored memories (i.e. what happened the last time we were in a similar situation).
If the situation is judged as being stressful, the HYPOTHALAMUS (at the base of the brain) is
The hypothalamus in the brain is in charge of the stress response. When a stress response is
triggered, it sends signals to two other structures: the pituitary gland, and the adrenal medulla.
These short term responses are produced by The Fight or Flight Response via the
Sympathomedullary Pathway (SAM). Long term stress is regulated by the Hypothalamic
Pituitary-Adrenal (HPA) system.
The Hypothalamic Pituitary-Adrenal (HPA) System
o The stressor activates the Hypothalamic Pituitary Axis
o The hypothalamus stimulates the pituitary gland
o The pituitary gland secretes adrenocorticotropic hormone (ACTH)
o ACTH stimulates the adrenal glands to produce the hormone corticosteroid
o Cortisol enables the body to maintain steady supplies of blood sugar
o Adequate and steady blood sugar levels help person to cope with prolonged stressor, and
helps the body to return to normal
The adrenal cortex releases stress hormones called cortisol. This have a number of functions including
releasing stored glucose from the liver (for energy) and controlling swelling after injury. The immune
system is suppressed while this happens.
Sympathomedullary Pathway (SAM)
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The hypothalamus also activates the adrenal medulla. The adrenal medulla is part of the autonomic
nervous system (ANS).
The ANS is the part of the peripheral nervous system that acts as a control system, maintaining
homeostasis in the body. These activities are generally performed without conscious control.
The adrenal medulla secretes the hormone adrenaline. This hormone gets the body ready for a
fight or flight response. Physiological reaction includes increased heart rate.…read more