The human organism regulates itself in every situation by contracting and expanding, pulsating between arousal and relaxation.
Circumstances that require you to exert yourself, such as having to work when tired, make you contract your muscles. Other types of annoying, frightening or demanding situation do the same. This is the action of the autonomic sympathetic nervous system, acting through the motor cortex and neuro-messengers.
As the muscles tense, various sphincters tighten, breathing quickens, the heart rate accelerates, blood vessels constrict, blood pressure rises, skin flushes, sweating increases, pupils dilate, senses narrow, and intestinal and glandular activity is reduced.
The chemical-hormonal aspect of this reaction is the release of stress hormones such as adrenaline and cortisol.
At the emotional level, you experience fear, anger or excitement.
At the behavioural level, you are roused to engage with the world, whether to fight a threat, to interact with another, to have sex, or to flee or hide from danger.
The balancing, calming function of the parasympathetic nervous system (especially the ventral vagus nerve) is what ultimately ensures that you do not become flooded or over-stimulated.
If the brain perceives overwhelming danger, the adrenaline release through the sympathetic nervous system can be so extreme that the parasympathetic response (dorsal vagus nerve) is not just to calm the body but to shut it down, a momentary ‘freeze’.
It is the ’emotional brain’ that decides, subjectively, what you perceive as danger. It jumps to conclusions based on rough similarities between past and present conditions.
Your personal map of the world was largely laid down in early childhood, when you had relatively few resources and were not able physically, intellectually or emotionally to stand up for yourself. Hence, some events in your current life which you ought be able to cope with in a logical manner are actually experienced by the organism as dangerous emergencies.
Original memory reception and recall seem to be stored in the same zones of the brain: what is wired together, fires together.
Faced with the conflicts and obstacles life throws in your path, you may enter a ‘freeze’ state, so that your rational brain, however briefly, goes offline, and you are disabled from making wise decisions. Or you enter ‘fight or flight’, reproducing a muscular-emotional-cognitive reaction to childhood events, and then you make poor choices that are really inappropriate to the present moment.
Inappropriate reaction patterns, loaded with personal history, lie at the root of stress management problems.