Chapter 6. Autonomic Nervous System

The autonomic nervous system regulates all internal processes of the body, i.e., the functions of internal organs and systems, glands, blood and lymphatic vessels, smooth and striated muscles (partially), sensory organs (Fig. 6.1). It provides homeostasis of the body, that is, the relative dynamic constancy of the internal environment and the stability of its basic physiological functions (blood circulation, respiration, digestion, thermoregulation, metabolism, excretion, reproduction, etc.). In addition, the autonomic nervous system performs an adaptive and trophic function — the regulation of metabolism relevant to environmental conditions.

Fig. 6.1. Autonomic nervous system (diagram): 1 — frontal cortex; 2 — hypothalamus; 3 — ciliary ganglion; 4 — pterygopalatine ganglion; 5 — submandibular and sublingual ganglions; 6 — auricular ganglion; 7 — superior cervical sympathetic ganglion; 8 — greater splanchnic nerve; 9 — splanchnic ganglion; 10 — celiac plexus; 11 — celiac ganglions; 12 — lesser splanchnic nerve; 12a — inferior splanchnic nerve; 13 — superior mesenteric plexus; 14 — inferior mesenteric plexus; 15 — aortic plexus; 16 — sympathetic fibers to the anterior branches of the lumbar and sacral nerves for the vessels of the legs; 17 — pelvic nerve; 18 — hypogastric plexus; 19 — ciliary muscle; 20 — iris sphincter muscle; 21 — iris dilator muscle; 22 — lacrimal gland; 23 — glands of the nasal mucous membrane; 24 — submandibular gland; 25 — sublingual gland; 26 — parotid gland; 27 — heart; 28 — thyroid gland; 29 — larynx; 30 — muscles of the trachea and bronchi; 31 — lung; 32 — stomach; 33 — liver; 34 — pancreas; 35 — adrenal gland; 36 — spleen; 37 — kidney; 38 — large intestine; 39 — small intestine; 40 — detrusor muscle (muscle that expels urine from the bladder); 41 — sphincter of the urinary bladder; 42 — sex glands; 43 — genitals; III, XIII, IX, X — cranial nerves

The term “autonomous nervous system” reflects the management of involuntary functions of the body. The autonomous nervous system depends on the higher centers of the nervous system. There is a close anatomical and functional relationship between the autonomous and somatic nervous systems. As part of the cranial and spinal nerves, autonomic nerve conducting tracts pass through. The neuron is the main morphological unit of the autonomic nervous system, as well as the somatic one, and the main functional unit is the reflex arc.

The following divisions are distinguished in the autonomic nervous system:

• central (cells and fibers in the brain and spinal cord);
• peripheral (all other structures).

There are also subdivisions:

• sympathetic;
• parasympathetic.

Their main difference is in the features of functional innervation and the effect of different mediators. The sympathetic part is excited by adrenaline, while the parasympathetic part is excited by acetylcholine. Ergotamine has an inhibitory effect on the sympathetic part, and atropine has an inhibitory effect on the parasympathetic part.