The determination of the range of norm variability, the boundaries of the transition of norm to pathology, and the study of the dynamics of the transition of adaptive reactions to pathological ones is a key link in understanding the pathogenesis and clinical manifestations of diseases in modern clinical medicine. The construction and angioarchitecture of the hemocirculatory bed are caused and directly related to the topographic and anatomical features of organogenesis, formation of the structuralfunctional units and, therefore, ensuring the functional purpose of the organ and its changes of an adaptive and pathological nature. The issues of angioarchitecture plasticity and tissue architecture of blood vessels walls of the hemocirculatory bed, in which adaptive mechanisms that compensate for hemodynamic disturbances and ensure the suffi ciency of blood circulation are implemented, need to be further developed. The identifi cation of systemic changes in vascular structural and functional modules can become an objective basis for the systemic association of diseases, the occurrence and development of which is reliably associated with the transformation of hemocirculatory architecture of organs. Determining the nature and dynamics of these changes can also contribute to the development of a systematic approach to the choice of treatment tactics and therapy for these diseases.

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Diseases of the sinoatrial node (SАN) are characterized by its inability to perform the function of the dominant pacemaker. This review presents data from recent studies of the anatomy and physiology of the SАN, which demonstrate the presence of structural and functional heterogeneity of the SAN and its components, describes the structure and function of the conducting intra-nodal pathways, the “novel paranodal area”, and also discusses the phenomenon of a shift in the site of excitation generation and the presence of a “non-firing mode” of cardiomyocytes. The authors critically discussed the genetic mechanisms of the development of sick sinus node syndrome (SSS), justified a multidisciplinary approach and further anatomical, morphological and physiological studies that play a fundamental role in the development of therapy and diagnosis of related diseases.

The unity of the organism and the ambient environment is realized by the nervous system and the humoral regulation. Based on this, all the variety of mechanisms for the functional activity regulation of the human body, experts traditionally classify into nervous and humoral processes, indicating that they are practically inseparable and constitute a united system. The advantages of one system compensate for possible shortcomings of the other, however, the vulnerability of the neuro-reflex mechanism of regulation is extremely high, and the state of knowledge of nervous regulation is higher, since it is amenable to registration by instrumental devices. At the same time, it is obvious that humoral regulation is one of the evolutionarily earliest mechanisms for regulating vital processes and, therefore, the most tested in practical use and, due to the preservation of this method of regulating homeostasis in the body, the most reliable and evolutionarily proven, but the study of humoral mechanisms regulation of the functions on the cellular and organ level is complicated by the vastness of subordinate tissues. Further painstaking research work is needed to study both the possibilities of humoral regulation in the human body and further study of the hemocirculatory system reactivity. This work can be the most important factor in the development of evidence-based medicine, validation of treatment policy for various pathological processes, objectification of control and estimated results of treatment.