[Structuro-functional Organization of the Vegetative (autonomic) Nervous System]

On the basis of a number of structural and functional indices, application of pharmacological analysis as well as recording of neuronal activity, the autonomic nervous system is subdivided into the sympathetic, parasympathetic and metasympathetic parts. The metasympathetic system includes the complex of microganglia situated in the walls of vosceral organs and having marked motility activity (the heart, ureters, intestine, stomach). According to the localization, separate areas of this system can be defined by its site (for example, the cardiometasympathetic area in the heart). The metasympathetic system attains the features of true autonomy. Its cells have no direct connection with the high centers: this connection is established through mono- and polysynaptic sensory and afferent units of sympathetic and parasympathetic nature. The system has a definite set of functional elements including sensory ones (mechano-, chemo- and thermosensitive those), oscillators, interneurons, tonic neurons. Neurons of the metasympathetic system are incorporated through interganglionic connections into the common functional network of the organ. A typical excitatory pattern suggests the presence of a temorary connection in the work of at least two neurons according to the "driver--follower" type. In addition to excitatory patterns there are also patterns showing inhibitory interactions. Besides well known systems of mediation including cholinergic and adrenergic ones, the metasympathetic system has its peculiar purinergic transmission.