Based on the multi-year research materials it has been established that the kidneys, are most sensitive organs to changes in metabolism. All conditions that cause an intensification of metabolism are accompanied by an increase in the kidney index. In this regard thereby, this trait can be considered as an adequate indicator of the scale of metabolism and is used as a kind of indicator of the level of population intensity of metabolic processes. The spleen index can be considered a specific indicator of the physiological condition of the organism, which is associated to the participation of spleen into red blood cell production and in specific biochemical processes associated with exchange of fatty acid and amino acids. The spleen plays a very important protective role and it acts as a blood deposit and as a blood filter. Hence the direct dependence of the spleen index on the intensity of the body's metabolism. A reliable direct dependence between the size of the adrenal glands and the intensity of their hormonal activity.was observed Moreover, any conditions that require a sharp intensification of metabolism in response to variety of stimulus cause hyperfunction of the adrenal glands. As result these can eventually lead to a stress adaptation syndrome - hormonal depletion, weakening and into death of the animal. In this context the size of the adrenal glands can be used as an indicator of the level of tension in the organism, caused by social factors, population density and by environmental conditions. A direct correlation between the size of the thymus and the viability of young animals, the specific course of the seasonal-age dynamics of the size thymus allows us to associate its role with the stimulation of energy processes in a growing organism and is considered an objective indicator of the biological age of voles. The length of the intestine and its sections serves as an indicator of the nutritional needs and nutritional characteristics of animals. Analysis of seasonal and age changes in the weight of the internal organs of Myodes glareolus makes it possible to single out six distinct phases in the postnatal period of its life cycle. The phases are characterized by certain characteristics of the main morphophysiological indicators, specific level of metabolic processes, and peculiarities of the seasonal ecology of individual intrapopulation groups of animals.