The definition of Stress; The Bodies response to Stress; Selyes GAS; The Sympathomedullary Pathway; The Pituitary-adrenal System.

HideShow resource information

Stress is...

Stress is a state of physiological or psychological strain caused by adverse stimuli [physical, mental, internal or external] that tends to disturb the functioning of an organism.

A Stressor is an event that triggers the stress response

Anything you percieve as something you can't cope with is a stressor.

Stress is about your perception of yourself and the world.

1 of 6

The Body's Response to Stress.

Sudden [or 'acute'] stress produces these bodily responses:

  • increase heart rate.
  • alterations in digestive activity.
  • Skin becomes pale.
  • Sweating.

Fight or Flight response.

Increase oxygen intake + Release stored glucose + Divert resources away from digestion = 

Ready to expend energy either by fighting or by running away.


  • An early evolutionary adaption that is useful in dealing with physical threats.
  • Helps us to deal with short term problems that can be solved via fighting or running.
  • Unfortunately, many of these threats we face in our society do not fall into these categories.
2 of 6

Selye's GAS.

Selye was the first doctor to study the stress response. His work is why we use the world 'stress' to talk about "Physiological and Psychological strain".

Selye found that stressors produced a similar physiological response in both animals and humans in three stages:

  • Stage 1 - Alarm: The Immediate response to stress. Cause by acute stressors.
  • Stage 2 - Resistance: When stress continues [becomes chronic] your body keeps up energy to resist it.
  • Stage 3 - Exhaustion: Energy reserves become depleted. At this point you can become ill.

Selye's work was pioneering, but it is not outdated. He discovered the symptoms of the physiological responses, but we now know the action biological systems involved.

3 of 6

Acute and Chronic Stress.

There are two biological systems involved. One corresponding with Selyes's Alarm stage, and the second corresponding with Selyes Resistant stage.

Acute Stress: A stressor immediately produces the fight or flight response through the sympathomedullary pathway.

Chronic Stress: If a stressful situation continues, the pituitary-adrenal system takes over. This helps us to resist and keep going for as long as possible.

These two responses both start when encountered with a stressor. It's just that the pituitary-adrenal system takes over to conserve energy.

Acute stress = Sympathomedullary pathway

Chronic stress = Pituitary-adrenal system.

4 of 6

The Sympathomedullary Pathway- Acute.

Hypothalamus activates SNS and stimuates the adrenal medulla.

SNS then prepares the body for the stressor.

The Adrenal Medulla releases adrenaline.

Andrenaline is released from adrenal medulla getting the body ready to deal with the stressor.

5 of 6

The Pituitary-Adrenal System - Chronic.

Hypothalamus stimulates the adrenal cortex.

This then stimulates the pituitary gland to release ACTH.

Which then releases corticosteriods.

The Liver then releases energy and the immune system is supressed.

6 of 6


No comments have yet been made

Similar Psychology resources:

See all Psychology resources »See all Stress resources »