The Mechanism Of Stress - Fight Or Flight

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In dangerous situations which may require a greater than normal level of physical activity (such as fighting or running away from an enemy), we have a self-protection system wired into our genes called the fight or flight response.

This is a reaction min out bodies and minds which makes us ready for massive physical exertion; it is controlled by the sympathetic branch of the autonomic (meaning self-regulating) nervous system. One of the functions of the sympathetic nervous system (SNS) is to control the release of the hormone adrenalin, which in turn raises the level of tension in the muscles of the body so that they are prepared for greater physical exertion. It also makes the heart pump faster and more deeply, thus producing that uncomfortable awareness of one's heart pounding away like a hammer in one's chest. Besides these physical effects, adrenalin also stimulates our feelings of fear, anger and exhilaration.

Other obvious bodily changes controlled by the SNS include: changes in the tension of the bowel and bladder sphincter muscles, diversion of blood from the skin and internal organs to the skeletal muscles (thus producing a pale face and a dry mouth), the halting of activity in the stomach and gut (producing "butterflies in the stomach" and that "sinking feeling"), and an increase in sweating as preparation to cool the body after any violent activity.

There are other, more subtle changes, too. For example, one's pupils dilate, and the walls of one's blood vessels constrict, thereby increasing blood pressure. The other branch of the autonomic nervous system - the parasympathetic - opposes all these changes. It has been called the "rest-digest" system because it reduces muscle tension, stores energy and encourages digestion.

The evolution of the fight-flight response allowed animals to react automatically to danger. The need for humans to prepare for a fight to the death or rapid escape mostly disappeared as we became more socialized, though even now the fight-flight response is still evoked when we are in danger. And, of course, this is fine if you do happen to need physical activity. Problems arise, however, because evolution has provided us with a thinking, conscious brain which allows us to perceive threats to our emotional well-being as well as threats of physical harm. In either case the result is the same: the subconscious switches on the fight or flight response.

Thus, for example, we sit through an examination or interview with a pounding heart, a tense body, an upset stomach, unable to think clearly and generally very aroused. (Arousal refers to the effects of a general increase in activity of the SNS, including the release of adrenalin and associated increase in mental activity.)

While mild arousal may pass almost unnoticed and slightly greater arousal may actually improve one's performance, higher levels of arousal are a major factor in various forms of anxiety. We shall look at these problems in more detail in a later chapter, but at the moment we are more concerned with the effects of a mild but persistent level of arousal. The kind of situation which raises adrenalin levels is very common in our society and our lives: a man under pressure at work, a woman at home bringing up the family under financial constraints, a couple trapped in an unhappy marriage - all these people and many more will habitually experience mild but persistent levels of arousal.

On the next page, we look at the physical and emotional effects of stress

 


Home ] [ Fight or flight - how stress works ] Physical and emotional effects of stress ] Good or bad stress? ] When stress becomes harmful ] Beliefs that make you stressed ] Test your own stress levels ] Reduce stress with holistic therapy ] Aromatherapy and Lumie bodyclock ] Treat your stress ] End your stress with relaxation ] Reduce your stress with self-hypnosis ] Reduce Your Stress With Diet ] Overcome the startle response ]