Ecology: The Biology of Interaction. V-09. Stress and Hormesis

V-9. Stress and Hormesis
(under development)
Contrary to popular belief, we should not — and indeed cannot — avoid stress. But we can use it and enjoy it if we learn more about its mechanisms and develop an appropriate philosophy of life.
Hans Selye
As established in 1936 by the Canadian scientist Hans Selye, the most diverse influences on the human organism and other animals elicit a similar response associated with the activity of the nervous and endocrine systems. Such a response is triggered by both physical (for example, adverse climatic conditions or high physical exertion) and psychological influences. These influences can be either adverse (such as grief) or favourable (including intense joy).
Stress (from the English stress — tension), or general adaptation syndrome, is the non-specific response of the organism to a variety of influences.
"It is not easy to imagine that cold, heat, drugs, hormones, sorrow and joy all cause the same biochemical changes in the body. Yet this is precisely the case. Quantitative biochemical measurements show that some reactions are non-specific and identical for all types of influences" (Selye, 1982).
The significance of stress lies in the fact that it increases the organism's capacity to adapt to changed conditions and adverse factors. According to Selye, a stress response to some influence can take two different forms, which often follow one another in sequence.
During eustress, the adaptive capacities of the organism expand. For example, in this state the organism is capable of compensating for adverse values of many ecological factors. It is known, for instance, that soldiers on the front line, enduring difficult conditions, very rarely catch colds and "recover" from many chronic illnesses. In a state of struggle for survival, the organism mobilises all its available energy reserves to adapt to harsh conditions. Often the eustress response allows the problems facing the organism to be resolved, and with that the stressful circumstances are exhausted. In the course of eustress, two phases can be distinguished: the alarm phase (the action of the factor that caused the stress) and the resistance phase, during which the organism's capacity to withstand influences increases.
It is worse when, despite the eustress response, the stressor continues to act and the organism's resources for adapting to adverse conditions are exhausted. Eustress is transformed into distress, to which the exhaustion phase corresponds. Distress is the adverse manifestation of stress, promoted by a reduction in resistance.
"Man was soon to discover that his reactions to prolonged and unusual severe trials — swimming in cold water, rock climbing, lack of food — follow a single pattern: first he feels difficulty, then he acclimatises, and finally he feels that he can bear no more. He did not know that this three-phase reaction is a general law governing the behaviour of living beings confronted with an exhausting challenge" (Selye, 1982).
In the worst case, distress can lead to death, and an inattentive observer may fail to understand what precisely caused it: the immediate cause of death may not be the factor that provoked the stress, but some other one. The described three-phase reaction (alarm phase — resistance phase — exhaustion phase) corresponds to the response of diverse organisms to adverse factors.