Het menselijk antwoord op stress: freeze, fight or flight
door Jon Law, 3 mei 2010
Originally coined by Harvard physiologist Walter Cannon “fight-or-flight” response, later extended to include freeze, describes the body’s automatic response to perceived threat or danger. A product of evolution this in-built safety mechanism is designed to protect not harm us. For the caveman, threats were best dealt with by freezing, when movement could alert the threat to his presence, by fighting if the odds were in his favour, but if not by fleeing.
For instance, when a caveman’s BBQ bison was on the go and a nearby monolithic bear smelt it, wanted it and came charging into the party uninvited, it’s a fair assumption that running away was the best option. If your survival mechanism wasn’t up to scratch you were bear food. Survival of the fittest ensured the stress response evolved to the marvel that it is. Unfortunately, in today’s society where bear threat is low, social stress and the freeze, fight or flight response are not compatible. Chronic social stress is a killer but acute stress in the form of danger from a potential attacker or impending disaster is not only valid but also highly valuable.
The stress response gives us the strength, power and speed to avoid physical harm to ourselves or significant others when we perceive danger. The sympathetic branch of the autonomic nervous system (the part responsible for subconscious body maintenance) initiates the fight-or-flight response, while the parasympathetic branch returns the body to homeostasis, calming us down and bringing everything back to normal in both emotional and physiological terms.
We perceive threat or danger, real or imagined and the sympathetic nervous system sets off a flood of emotional and physiological activity which enables us to increase power, speed and strength as required. The amygdala, sounds the alarm’ and the hypothalamus notifies all the other systems in the body via the nervous system, while instructing the endocrine system to begin the secretion of powerful hormones, mainly adrenaline and cortisol. These flood into the bloodstream and activate cells to aid the preparation to freeze, fight or flight.
This internal activity results in many complex changes with the purpose to divert resources from unnecessary functions to systems vital in the process of increasing speed, power and strength. These changes include increased heart rate, blood pressure, breathing rate, brain activity and blood flow being redirected to the muscles (vascular shunt) while digestion, the immune system and the reproductive system for example are switched off. We are hardwired to resist threat and be able to protect ourselves from danger. This system is poetry in motion, the stress response is a powerful, useful process which kicks in as reliably as flicking a switch once danger is perceived.