Plan
► Concept of adaptation. Kinds of adaptation. Specific and non-specific manifestations of adaptation.
► Non-specific adaptation syndrome (stress). Stages of stress.
► Concept of stressors and stress-related diseases.
Concept of Adaptation. Kinds and Manifestations of Adaptation
Adaptation is understood as a totality of congenital and acquired physiological mechanisms aimed to adjust an organism to the environment. Adaptive responses are realized on all levels of organization of an organism: cell, tissue, organ, system, organism and population levels.
On an organism level adaptation can be manifested by three ways:
► escape of an organism from the situation associated with exposure to factors requiring adaptation;
► passive adaptation;
► active adaptation.
Adaptation to low temperatures is different in different living organisms. Some organisms escape from the region of low temperature, e.g., in autumn many birds fly away to the south from northern areas. Some animals, e.g., frogs, fall into anabiosis. Other animals actively counteract this environmental factor by changing their heat production and heat dissipation processes, by active search for shelter, and so on.
Adaptation mechanisms are divided to short-term and long-term mechanisms. Short-term mechanisms come into play immediately after action of a stimulus and may last from several seconds to several days. Short-term mechanisms are mainly associated with the activity of the sympathoadrenal system. As a rule, they do not result in any structural alterations in the body. Long-term adaptation mechanisms provide a long-lasting adaptation of the body
to the factors and replace the short-term mechanisms of adaptation. Long-term mechanisms leave structural traces evidencing anatomical alterations.