Ecology: Biology of Interaction. 5.10. Selye’s Concept of Stress
As established in 1936 by Canadian scientist Hans Selye, very different effects on humans and other animals can trigger a similar response associated with nervous and endocrine system activity.
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5.09. “Interaction of factors” and the Hutchinson niche
D. Shabanov, M. Kravchenko. Ecology: Biology of Interaction Chapter 5. Autecology and Foundations of Environmental Science
5.11. Organism features associated with size
5.10. Selye’s stress concept Contrary to common opinion, we must not — and cannot — avoid stress. But we can use it and even enjoy it if we understand its mechanisms better and develop an appropriate philosophy of life. Hans Selye As Canadian scientist Hans Selye established in 1936, very different impacts on humans and other animals trigger a similar response associated with nervous and endocrine system activity. This response may be triggered both by physical effects (e.g., adverse climatic conditions or high physical load) and by psychological effects; these effects may be adverse (such as grief) or favorable (such as intense joy). Stress (from English stress — strain), or the general adaptation syndrome, is a nonspecific organism response to diverse impacts. “It is not easy to imagine that cold, heat, drugs, hormones, sadness, and joy can cause the same biochemical shifts in the organism. Yet this is exactly the case. Quantitative biochemical measurements show that some responses are nonspecific and identical for all kinds of impacts” (Selye, 1982). The significance of stress is that it increases organism capacity to adapt to changed conditions and adverse factors. According to Selye, stress response to a given impact may be expressed in two different forms, often sequentially. During eustress, organism adaptive capacity expands. For example, in this state the organism can compensate for unfavorable values of many ecological factors. It is known, for instance, that on the front line, under severe conditions, soldiers rarely suffer from colds and are “cured” of many chronic diseases. In survival mode, the organism uses all available energy reserves to adapt to harsh conditions. Often eustress response solves the problems facing the organism, and the stressful situation is thereby exhausted. Two phases can be distinguished within eustress: alarm phase (action of stress-inducing factor) and resistance phase, when organism ability to withstand impacts increases. It is worse if the stressor continues despite eustress response. Organism capacity to adapt to adverse conditions becomes depleted. Eustress turns into distress, corresponding to exhaustion phase. Distress is an unfavorable manifestation of stress associated with reduced resistance. “Humans must have discovered early that their responses to prolonged and unusual severe challenges — swimming in cold water, climbing rocks, lack of food — follow one pattern: first difficulty is felt, then adaptation occurs, and finally one feels unable to endure more. They did not know that this three-phase response is a general law of behavior of living beings confronted with an exhausting task” (Selye, 1982). In the worst case, distress can lead to death, and an inattentive observer may not understand what caused it: immediate cause of death may be not the factor that induced stress, but another one. The described three-phase response (alarm phase — resistance phase — exhaustion phase) corresponds to reactions of various organisms to adverse factors. 5.09. “Interaction of factors” and the Hutchinson niche
D. Shabanov, M. Kravchenko. Ecology: Biology of Interaction Chapter 5. Autecology and Foundations of Environmental Science
D. Shabanov, M. Kravchenko. Ecology: Biology of Interaction, Chapter 5. Autecology and Fundamentals of Environmental Science
5.11. Organism features associated with size