Human Anatomy - Kotsan I. Ya. 2009

Autonomic (Vegetative) Nervous System

The Autonomic Nervous system (systema nervosum autonomicum) is an integral part of the body's unified nervous system. Both names of this system are somewhat conventional. Literally, the term "autonomous" means self-regulating, while "vegetative" (autonomic) implies organic or vegetative Functions. Because the Organism functions as a unified whole in which all structures are interconnected, and no organ or system is entirely self-regulating, "autonomous" denotes only a relative self-regulation within The Nervous System's activity, meaning its independence from conscious control. At the same time, however, the entire activity of the autonomic nervous system remains under the control of the Cerebral Cortex.

It was previously believed that the autonomic nervous system innervates only the so-called Organs of vegetative life, which included all Internal Organs (specifically those of the digestive, respiratory, urinary, and reproductive systems), cardiovascular organs, endocrine and exocrine glands, and other structures containing Cytology/cytology/32.html">Smooth Muscle tissue and Glandular Epithelium. However, the autonomic nervous system also innervates Striated muscle tissue (trophic innervation), regulating its metabolic processes and tone.

Thus, the autonomic nervous system (from Latin vegeto – to arouse, enliven) coordinates and regulates The activity of internal organs, METABOLISM, the constancy of the body's internal environment (Homeostasis), and the functional activity of Tissues, as well as providing secretory and trophic innervation.

It is known that Changes in the state of Higher Nervous Activity are reflected in the functions of internal organs and, conversely, changes in the body's internal environment influence the functional state of the nervous system. The autonomic nervous system enhances or diminishes the function of specifically active organs. This regulation is tonic in nature. Since a single nerve fiber can act in only one direction and cannot simultaneously increase and decrease tone, the autonomic nervous system is accordingly divided into two divisions (parts): the sympathetic and the parasympathetic.

In terms of its primary functions, the sympathetic division is organ-stimulatory. It adapts the organism to conditions of intense activity that involve high Energy Expenditure: this is accompanied by accelerated Heart rate, increased pulmonary ventilation, elevated metabolism, and other responses.

The parasympathetic nervous system performs a protective function (organ-preserving) – it promotes the restoration of energy reserves in Cells, enhances assimilation processes, and facilitates the removal of Metabolic waste products from the body.

Comparing the distribution areas of sympathetic and parasympathetic innervation reveals, first, the predominant significance of one or the other autonomic division. The Urinary Bladder, for instance, receives predominantly parasympathetic innervation, and the transection of sympathetic nerves does not significantly alter its function; conversely, Sweat Glands, arrector pili Muscles, the Spleen, and the Adrenal Glands receive exclusively sympathetic innervation. Second, in organs with dual autonomic innervation, an interaction between sympathetic and parasympathetic nerves is observed in the form of a distinct antagonism. For example, stimulation of sympathetic nerves causes pupil dilation, vasoconstriction, accelerated heart rate, and inhibition of intestinal peristalsis, whereas parasympathetic stimulation leads to pupil constriction, vasodilation, slowed heart rate, and enhanced peristalsis. However, the so-called antagonism between the sympathetic and parasympathetic divisions should not be understood statically as a direct opposition of their functions. These divisions interact, and the ratio between them changes dynamically across different phases of a given organ's function; they can act both antagonistically and synergistically.

Antagonism and synergy are Two Sides of a single process. The normal functions of our organism are ensured by the coordinated action of both Divisions of the autonomic nervous system. This coordination and regulation of functions are carried out by the cerebral cortex with the participation of the reticular formation.

The Influence of sympathetic and parasympathetic nerves on organ functions is shown in Table 13.

Class="center">Table 13 EFFECT OF SYMPATHETIC AND PARASYMPATHETIC NERVES ON ORGAN FUNCTIONS

In its Structure, the autonomic nervous system is similar to the somatic (animal) nervous system. It also comprises central and peripheral divisions (parts).

The centers of the autonomic nervous system are located in the Spinal Cord and brain. They are divided into suprasegmental (higher) and segmental (lower) levels. The coordinating influence of segmental centers extends to specific functions and is exerted via distinct segmental nerves (hence the name of these centers). Suprasegmental centers coordinate the functions of effector organs through multiple segmental centers, as well as by interacting with other regulatory systems – endocrine, circulatory, and others. Furthermore, suprasegmental centers not only coordinate autonomic functions (Respiration, Circulation, Digestion, excretion, reproduction) but also integrate them with somatic functions (striated Muscle contraction and information exchange with the external environment), thereby determining human behavior as a whole.