The stress response is a strictly coordinated, finely tuned biological process.
Any influence on the body which threatens to upset its equilibrium is a stress factor which initiates a stress response, irrespective of whether the stress factors are of a physical or psychological nature.
Generally the stress response occurs subconsciously. Extreme situations in particular require a perfectly coordinated biological stress response. That response is activated, controlled, and curbed by the immune system, the central nervous system with its sensomotoric elements, the autonomous nervous system (sympathetic and parasympathetic nervous system) and hormones like glucocorticoids and catecholamines. All of these systems interact and have a reciprocal effect on one another.
They are referred to in their entirety as the stress system.
This astonishing network of multi-layered, interconnected regulatory cycles is modulated externally by perceptions and associated interpretations, by molecules and microbes that constantly exert pressure on the immune system via the mucous membranes of the intestines and lungs, and by a host of stimuli inside the body such as blood pressure, body temperature and blood sugar levels.
The brain regulates, controls and coordinates the basic activities of our body and the stress response process. Special centres within the central nervous system (CNS) fulfil those roles. To some extent they are measuring centres that constantly analyse both target and actual levels.
Once again there are positive and negative feedback loops and a host of different regulatory cycles between these centres ensuring the precise sequence and adjustment of processes at the periphery of the body.
The activities of the immune system are controlled and curbed by the autonomous nervous system. These processes occur in real time. Like the CNS, cortisol control loops contribute to the process of curbing excessive immune reactions. The cortisol system is therefore always highly active during periods of stress.
Because of its immunosuppressive and anti-inflammatory effect, cortisone is also a popular choice of therapy. Many of you will have already experienced the pain-killing effects of cortisone.
Following a brief active phase in the initial phase of the stress response all systems strive to keep the stress response under control. Otherwise inflammation that constantly occurs in, for instance, the mucose membranes of the stomach and bowel, the bronchial tubes and lungs or during muscular activity, would spread throughout the body. Depending on a person's genetic disposition, the door is thus wide open to all kinds of disease when someone is under permanent stress.
Also there is a big difference between acute and chronic stress. Acute stress situation we usually are digesting quite well compared to chronic stress often leading health issues.