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Stress - How Does It Work?

Updated on March 17, 2014
Fortunately losing stripes isn't a symptom of stress, in humans at least.

What Is Stress?

Stress occurs when the environmental, physical or social demands in a persons life exceeds what they think that they can cope with.

When the demands that people experience are thought of as damaging to their well-being then they will become stressed.

Stressors that we experience in our everyday lives are now a lot more psychological than they used to be, for instance the stress of going to work or school every day. However, in the past our ancestors stressors would be more physical because the changes that their body experienced as a result of stress were essential to their survival - for example hunting for food.

They way that our bodies respond to stress involves two main systems. The first system is the sympathomedullary pathway which is the response that we have to 'acute' stressors and the second is the pituitary-adrenal system which is the response that we have to 'chronic' stressors.

The Sympathomedullary Pathway

  • Acute stressors, for example animals getting chased by a predator, will arouse the autonomic nervous system (ANS).
  • The ANS is split into the sympathetic nervous system (SNS) and the parasympathetic branch.
  • The SNS arouses the animal to be ready for 'fight-or-flight' and the parasympathetic branch relaxes the animal back to a normal state.
  • Neurons are then sent from the SNS to virtually every gland and organ in the body. This causes an increase in blood pressure and heart rate.
  • At the same time that the SNS is activated, the sympathetic adrenal medullary system (SAM) is activated and stimulates the adrenal medulla (the middle of the adrenal gland) to release adrenaline into the blood stream.
  • The effects that the adrenaline has includes increasing the oxygen and glucose supply to the brain and muscles and suppresses bodily functions such as the digestion.

A helpful video for remembering the two different responses to stress

The Pituitary-Adrenal System

  • The Pituitary-Adrenal System is activated when a person is exposed to chronic stressors and is a lot harder to initiate than the sympathomedullary pathway.
  • When the higher centers of the brain perceive stressors the hypothalamus (a small cone-shaped part of the brain) is activated and releases a chemical called corticotrophin-releasing factor (CRF) into the bloodstream.
  • The CRF then travels to the pituitary gland where it causes it to release a hormone called ACTH.
  • ACTH then travels in the blood stream until it reaches the adrenal gland where it stimulates the adrenal cortex to release cortisol which then causes several stress related effects including:
  • bursts of energy
  • lower pain sensitivity
  • lower immune response
  • higher blood pressure
  • It takes about 20 minutes for this whole process to carry out.

On a scale of 1-5 (1 being not stressed and 5 being highly stressed) how would you rate your day to day stress levels?

See results

Stress and the immune system - Kiecolt-Glazer et al.

in 1984 Kiecolt-Glazer et al conducted an experiment to see whether acute stressors had a negative effect on the immune system.

They took a blood sample of some medical students a month before their exam and the time around their exam. NK cell activity in the blood was measured in order to see how well their immune system was functioning.

They found that from the blood sample that was taken around the time of their exams there was a significantly lower number of active NK blood cells.

These results suggest that the more acute stressors that you experience, the more likely it is that your immune system will be functioning poorly and therefore the more susceptible you will be to illness.

In 2005 Kiecolt-Glazer once again conducted an experiment into the functioning of the immune system, but this time she measured the time taken for blister wounds to heal on people who were currently under stress due to interpersonal conflict.

She studied married couples that were having conflicting conversations rather than supportive ones and then saw how long it took after that conversation for the wound to heal.

She found that conflicting couples had a weaker immune system and thus took more time to heal than supportive couples.

As you can see from this hub, stress can be damaging to your mental and physical health. If you feel that you suffer from too much stress on a day-to-day basis then the NHS website has some tips that could help you try to cope with it.


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    • Anthropophobia profile imageAUTHOR


      5 years ago

      I'm glad I could help! Thanks for reading :)

    • Joe Salmon 117 profile image

      Joe Salmon 

      5 years ago from Newport, Isle of Wight

      This is one of the biggest gaps in my knowledge that I know of, and you have just minimised that ten fold, thanks!

    • osaeoppongde profile image

      Deborah L. Osae-Oppong 

      5 years ago from Chicago, IL

      Very timely! I'm feeling it right now! Thanks for the information!

    • Anthropophobia profile imageAUTHOR


      5 years ago

      Thank you! I believe it too as I always feel ill after exams or other such stressful events. Thanks for stopping by.

    • thebiologyofleah profile image

      Leah Kennedy-Jangraw 

      5 years ago from Massachusetts

      Another interesting read-thanks for sharing. I definitely believe the connection between the immune system function and stress as I have seen it in action, great examples of research done to support it.


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