Most people with anxiety states are simply more alert and aroused than the general population. The chemical processes which underlie anxiety are complex but essentially lead to the body being put into an optimum state of preparedness.
One way of looking at anxiety is that the body goes into this state of preparedness without a rational external reason. For many anxiety sufferers there is a simple cure which activates an attack.
This may be the sight of a spider, the thought of going shopping or talking to a large group of people. Attacks of anxiety like this can be managed by the exposure based approaches which have been shown to be so effective.Read more on nopanic.org.uk