Autonomic nervous system

The autonomic nervous system refers to the involuntary and largely subconscious division of the peripheral nervous system that regulates visceral functions. These include cardiovascular activity, respiratory rhythm, digestive processes, glandular secretion, thermoregulation, and pupillary reflexes. It operates independently of conscious control and is essential for maintaining homeostasis across all domestic animal species.

The autonomic nervous system is anatomically and functionally divided into two primary subdivisions: the sympathetic part and the parasympathetic part. These divisions consist of preganglionic neurons, whose cell bodies are located in the central nervous system, and postganglionic neurons, which innervate the target organs. Preganglionic fibers of the sympathetic system originate from the thoracolumbar spinal cord segments, whereas those of the parasympathetic system arise from craniosacral regions, particularly cranial nerves III, VII, IX, and X, as well as sacral spinal nerves.

Communication between the autonomic nervous system and visceral organs is mediated through a network of autonomic plexuses, such as the cardiac, celiac, and pelvic plexuses, which integrate sympathetic and parasympathetic fibers. These plexuses are embedded within connective tissue surrounding major organs and blood vessels, forming intricate regulatory circuits.

From a clinical and anatomical perspective, understanding the pathways and effects of the autonomic nervous system is essential in veterinary practice, particularly in anesthesia, pharmacology, and the diagnosis of neurologic or systemic diseases. The anatomical organization of the autonomic system varies slightly among species but remains fundamentally conserved in all mammals.