Tuesday, August 15, 2006


This article provides an insight into what happens at a physiological level when a person becomes stressed. Although this article may seem rather complicated, it is an oversimplification of what happens. It is suggested that readers interested in increasing their understanding about this topic refer to advanced texts that are available.

The Stress Response
When people perceive that they are in threatening situations that they are unable to cope with, then messages are carried along neurones from the cerebral cortex (where the thought processes occur) and the limbic system to the Hypothalamus. This has a number of discrete parts.

The Anterior Hypothalamus produces sympathetic arousal of the Autonomic Nervous System (ANS). The ANS is an automatic system that controls the heart, lungs, stomach, blood vessels and glands. Due to its action we do not need to make any conscious effort to regulate our breathing or heart beat. The ANS consists of two different systems: the sympathetic nervous system and the parasympathetic nervous system. Essentially, the parasympathetic nervous system conserves energy levels. It increases bodily secretions such as tears, gastric acids, mucus and saliva which help to defend the body and help digestion. Chemically, the parasympathetic system sends its messages by a neurotransmitter called acetylcholine which is stored at nerve endings.

Unlike the parasympathetic nervous system which aids relaxation, the sympathetic nervous system prepares the body for action. In a stressful situation, it quickly does the following:
Increases strength of skeletal muscles
Decreases blood clotting time
Increases heart rate
Increases sugar and fat levels
Reduces intestinal movement
Inhibits tears, digestive secretions.
Relaxes the bladder
Dilates pupils
Increases perspiration
Increases mental activity
Inhibits erection/vaginal lubrication
Constricts most blood vessels but dilates those in heart/leg/arm muscles

Copyright 2000, Stephen Palmer

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