The Alarm Reaction
The human body and human mind each have a set of very important and very predictable responses to threat. Threat may come from an internal source, such as pain, or an external source, such as an assailant. One common reaction to danger or threat has been labeled the "fight or flight" reaction. In the initial stages of this reaction, there is a response called the alarm reaction .
Think about what happens when you feel threatened. Your racing heart, sweaty palms, nausea, and sense of impending harm are all symptomatic of this alarm reaction.
When a person perceives a threat, the initial stages of a complex, total-body response will begin. The brain orchestrates, directs, and controls this response. The more threatened an individual feels, the further their brain and body will be shifted along an arousal continuum in an attempt to ensure appropriate mental and physical responses to the challenges of the threat. The cognitive (thinking), emotional, and behavioral functioning of the individual will all reflect this shift along the arousal continuum.
During the traumatic event, all aspects of the individual's functioning change, including feeling, thinking, and behaving. For instance, someone under direct assault abandons thoughts of the future or abstract plans for survival. At that exact moment, all of the victim's thinking, behaving, and feeling is being directed by more primitive parts of the brain.
A frightened child in a threatening situation doesn't focus on the words being spoken or yelled; instead, he or she is busy attending to the threat-related signals in their environment. The fearful child will key in to nonverbal signs of communication, cues such as eye contact, facial expression, and body posture, or proximity to the threat.
The internal state of the child also shifts with the level of perceived threat. With increased threat, a child moves along the arousal continuum from vigilance through to terror. (See the above graph for different possible response scenarios.)
The Arousal Continuum
The arousal continuum is characterized by many physiological changes. Under threat, sympathetic nervous system activity increases in a gradual fashion. Heart rate, blood pressure, and respiration are altered during the arousal response. Glucose stored in muscle is released to prepare the large skeletal muscles of your arms and legs for either a fight or a flight.
These changes in the central nervous system cause hypervigilance; under threat, the child tunes out all non-critical information. These actions prepare the child to do battle with or run away from the potential threat.
This total body mobilization -- the fight-or-flight response -- has been well characterized and described in great detail for adults. These responses are highly adaptive and involve many coordinated and integrated neurophysiological responses across multiple brain areas, including the brainstem nuclei responsible for autonomic nervous system regulation.
What Does Hyperarousal Really Mean?
Hyperarousal is a multi-dimensional process characterized by both mental and physical changes. These include an increase in the activity of those parts of the central and peripheral nervous system responsible for the perception and processing of potentially threatening information . This graded response also involves action.
During the hyperarousal process, many physiological systems required for survival are activated (e.g., stress response hormones such as cortisol and adrenaline). The many physiological changes during hyperarousal will influence the way a person thinks, feels, and acts.