Threat initially arouses the sympathetic nervous system, causing the person in danger to feel an adrenalin rush and go into a state of alert. Threat also concentrates a person's attention on the immediate situation. Finally, threat evokes intense feelings of fear and anger. These changes in arousal, attention, perception, and emotion are normal, adaptive reactions. They mobilize the threatened person for strenuous action, either in battle or in flight.
Traumatic reactions occur when action is of no avail.
When neither resistance nor escape is possible, the human system of self-defense becomes overwhelmed and disorganized. Each component of the ordinary response to danger, having lost its utility, tends to persist in an altered and exaggerated state long after the actual danger is over. Traumatic events produce profound and lasting changes in physiological arousal, emotion, cognition, and memory. More-over, traumatic events may sever these normally integrated functions from one another. The trauma-tized person may experience intense emotion but without clear memory of the event, or may remember everything in detail but without emotion.