The Physiology of Stress

The Physiology of Stress

Our bodies’ reaction to stress is rooted in our ancestry. In earlier times, stress had a survival
value. All animals have inherent in them an emergency reaction to get themselves out of
danger quickly. This is what is often called the ‘Fight or Flight’ or ‘Alarm’ reaction. When
the mind perceives a threat the ‘Alarm Button’ or hypothalamus in the brain is pressed.

The brain then sends out messages to different parts of the body, which is immediately
prepared for action, system by system.

1. The muscles - become tense.
2. The adrenal glands - these are situated above our kidneys and release stress
hormones to get the reaction going and sustain it.
3. The heart - beats faster. Blood pressure rises. The major blood vessels dilate and
more blood is therefore sent to vital organs e.g. the muscles needed to run away or
to fight.
4. The lungs - faster breathing increases the oxygen supply to produce energy, and
eliminate the waste carbon dioxide.
5. The liver - releases glycogen (stored sugar) into the blood supply, raising blood
glucose for energy
6. Stored fats - are released, again for use as energy by the muscles.
7. The skin - sweats to keep us cool.
8. The eyes - pupil dilates to improve our sideways vision to find a way of escape.
9. The digestive system - slows down and almost stops temporarily, as the blood is
diverted to more important organs e.g. muscles. The food stays longer in the
stomach, the bowel slows down and the bowel sphincters close.
10. The bladder sphincters close.

There are many other changes, but these are the most important. This reflex was a lifesaver
for our prehistoric ancestors who had to ‘fight’ or ‘flee’ regularly to save their lives.
Occasionally, it is useful for us if we need to respond very rapidly on a physical level to a
threat - for example, if we are charged by a bull whilst sitting in a field! A surge of energy
will help us reach the gate in time. It is an emergency reaction for use in the short term only,
followed by a time for ‘winding down’ after the chase or the fight, during which the affected
organs in the body can return to normal. Problems develop when the reaction is sustained
for longer periods as happens too frequently in the present day and in war-torn regions.

The perceived ‘threats’ in modern society are less likely to be physical attacks on us.
Rather, they take the form of psychological pressures resulting from the many different and
often conflicting demands made on us, as we attempt to fulfill expectations laid on us in our
various roles as workers, parents, partners, colleagues, friends etc. When experiencing
‘distress’ the body systems are put out of balance and then remain in this state, resulting
all too often in ill health. The irony is that what was intended as a life saving reflex is now
one of the major causes of serious illness in our society.