Stress response

The stress response, commonly known as the fight-or-flight reaction, is the first part of so-called General Adaptation Syndrome (GAS). It's a short lasting physical reaction of the body (or organism) towards the real (or even any imagined) threat. This response can be seen from multiple of levels - molecular, cellular, anatomic or atomic. It can be defined by physical or/and chemical processes which are triggered by it, or by any physical symptoms on the perception level. Or by some other means.

Three phases of GAS are:

1. stress response (fight-or-flight reaction)
2. resistance
3. exhaustion

So in the hypothetical situation where your life is in danger and you are forced to run away, the first part is very explosive and effective accumulation of energy at your disposal. If the threat persists, the next phase called resistance, is much longer sustainable state of increased level of disposable energy, but decreasing with time. After a while, depending on physical condition of that particular person, the third phase called exhaustion will follow. This is the state where the most of the energy is already spent, and the body is no longer in a position to fight or flight anymore. 

But from those three phases the first one is by far most interesting, so let's go deeper into particular physiological and chemical changes that are triggered by the stress response. It's all happening in real time, so the stress response is occurring on the observable level (to a certain degree of course). The consequences of the stress response could be put into two broad categories:

a) short-term consequences

b) long-term consequences

and those two differ substantially, so let's elaborate both of them.

SHORT-TERM

In the short-term, the stress response can be useful and helpful by presenting some information (a lesson learned), the impulse for the body to improve, or get stronger. In the short-term, it can be even perceived as a pleasurable event, providing it's happening within well-known boundaries (like for example in adrenalin sports). But it can be harmful in the case when the impulse is too strong to handle, and it slips the person into any negative experience of stress. And in the big proportions we talk about trauma (on mental level) or the injury (on physical level).

The principle behind the stress response in the short-term is to provide the organism the opportunity to improve, or strengthen itself in some way. Providing there is the sufficient and quality recovery time, and handling the stress is still manageable (to the comfortable level), the result should be the improvement of the body in dealing with that particular type of stress or condition.

The analogy could be used of learning how to drive the car. The frustration and stress associated with handling new circumstances evoke the stress response on the number of occasions. But if handled, it leads into the ability of driving the car, which in turn becomes a very useful skill in life.

LONG-TERM

By the long-term consequences of stress response I don't mean cyclical and continual short-term stress response with recovery time on day-to-day basis. But mainly it means some degree of continual residue of stress, which hasn't been handled within the manageable (or comfortable) level. Or, in the case when there isn't sufficient recovery time provided to the organism, even if the impulse itself is handled well. This stress is not really used for an improvement of the organism, but instead it builds up as some form of toxic substances within the body, or it can manifest as the lack of useful (energy) substances in the body.

Now here, we really talk about quite negative consequences of the stress response. Those can be recognizable on physical level, as well as on the perception level. It's roughly summarized in the flow diagram bellow:

Noise, heat, infection, isolation, aggression, and many more other factors persisting in the experience of the individual, can lead into some sort of negative long-term consequences of the stress response. Concrete physical symptoms then follow, for example the memory loss, the rapid (unhealthy) weight loss, ulcers, heart diseases, loss of sexual function, and many many others.

DISSECTION OF STRESS RESPONSE:

Once we have cleared the function of it, and the differences between long-term and short-term, we can now go deeper into many particular changes within the body. For easier grasping of so many processes, I created a simple list of direct physical and/or chemical processes that follow immediate stress response. In brackets, I present the particular hormone, which is responsible for that particular physical response - even if only in those cases (of course) where it can be determined. So simply put, the stress response causes:

- increased heart rate (adrenalin)
- increased blood pressure (noradrenalin)
- decreased pain sensitivity (endorphines)
- stopped/slowed down the activity of digestive system (cortisol)
- stopped/slowed down the activity of reproductive system (cortisol)
- alerted mind (adrenalin)
- enriched blood with:
    a) glucose  (glucagon)
    b) fatty acids (cortisol)
- started up/kicked in of the immune system (ACTH)
- started up the proliferation (building up) of T-cells
- inhibited production of GH (growth hormone)
- stimulated release of CRH from hypothalamus into blood
- stimulated anterior pituitary to release ACTH
- stimulated cortisol synthesizing from cholesterol in adrenal cortex
- increased carbohydrate metabolism (glucagon, cortisol)
- stopped/slowed down the tissue repair (less GH)
- increased rate of blood circulation (adrenalin+noradrenalin)
- enhanced memory formation (adrenalin)
- increased signalling of sympathetic part of nervous system
- suppressed signalling of parasympathetic part of nervous system
- prepared body to deal with challenges (adrenalin)
- inhibited inflammatory response (cortisol)
- suppressed stomach activity
- reduced secretion of digestive acids
- decreased blood flow to the walls of the stomach
- slowed down epithelial cell replacement in the gut
- reduced thickness of mucous membrane in the gut
- reduced production of reproductive hormones
- loss of sexual desire (less testosterone)
- disruption of sexual performance (less testosterone)
- enhanced brain activity - agility - learning
- more relaxed lung muscles - prepared for more oxygen getting in
- increased volume of lungs / their effectiveness