The Nature of Stress

In medicine, stress may be defined as a ‘Physical or psychological stimulus that can produce mental tension or physical reactions that may lead to illness’.

In our bodies we have an autonomic nervous system which controls many of the automatic activities of our bodies.  For example, whether we are asleep or awake, our autonomic nervous system makes sure that our temperature, heart rate, breathing, blood pressure and other bodily functions are all kept within normal limits with no effort on our part.

This autonomic nervous system divides into the sympathetic and the parasympathetic systems; and, like the arms of a see-saw, only one of them can be up (active) at any one time.

Stress activates the sympathetic part of the autonomic nervous system and causes the release of stress hormones including adrenaline and cortisol. 

Whenever we encounter a stressful event, our bodies undergo a series of hormonal and biochemical changes that put us in alarm mode.  We all recognise the effects such as dry mouth, muscle tremor, sweating and racing pulse as adrenaline rushes through our blood stream.

This 'fight or flight' response has an ancient evolutionary heritage where the body 'thinks' it has to run away or stand up and fight.  When this physiological response evolved in cave-man days, it was of great value.  It gave us a burst of power as we ran away from a sabretooth tiger or fought with the tribe in the next valley.  However, it’s not such a useful response when the stressful event is getting stuck in a traffic jam on the way to work.

While we are in ‘fight or flight’ mode, less blood flows to the digestive system and other non-muscle organs. Our digestive and immune systems, which are controlled by our parasympathetic system, temporarily shut down.  Absence of the autonomic parasympathetic activation leads to poor digestion and probably also to poor healing and immune function.

In contrast, when the parasympathetic system is active, the bowel and other non-muscle organs receive good blood-flow and all the glands function well to secrete their various compounds.

When we are rushing off to work in the morning, getting the kids to school or in the office working hard, the body is in sympathetic ‘flight or fight’ mode.  In order to digest that breakfast that was eaten standing at the kitchen counter or that lunch that was grabbed to eat at the desk; the body requires parasympathetic mode. In other words, the ‘flight or fight’ needs to be switched off in order for digestion to begin.  This doesn’t happen in an instant and requires time to sit, relax and enjoy the food.

Our modern lifestyle tends to cause continual sympathetic nervous system activation with very little opportunity for the parasympathetic nervous system to activate.

Prolonged sympathetic activity inhibits the immune response and we are more susceptible to infection during periods of stress.  It is thus vital to take time out to allow for rest and proper parasympathetic action in our bodies.  None of us can avoid stress, but we can look after ourselves.

Common causes of stress are-

• Events such as births, deaths, weddings and moving house.
• Responsibilities such as unpaid bills and lack of money.
• Work or study such as exams, project deadlines and excessive commuter travel.
• Personal relationship issues such as dissatisfaction, conflict and deception.