preganglionär

Preganglionär refers to the neurons or nerve fibers whose cell bodies are located in the central nervous system and that project to autonomic ganglia where they form synapses with postganglionic neurons. These preganglionic cells are key elements of the autonomic nervous system, connecting the CNS to the visceral organs.

In the sympathetic division, preganglionic neurons reside in the intermediolateral cell column of the spinal cord, mainly in segments T1 to L2. Their axons are relatively short and exit via the ventral roots to form part of the sympathetic chain or to reach prevertebral (collateral) ganglia, where they synapse with postganglionic neurons. Postganglionic fibers are longer and extend to target organs. Preganglionic sympathetic fibers are typically myelinated and release acetylcholine onto nicotinic receptors on postganglionic neurons; postganglionic fibers then release norepinephrine in most targets, with exceptions such as sweat glands, where acetylcholine is released.

In the parasympathetic division, preganglionic neurons originate in brainstem nuclei (cranial nerves III, VII, IX, X) and in the sacral spinal cord (S2–S4). Their axons are long and synapse on terminal or intramural ganglia located near or within the visceral organs. Both preganglionic and postganglionic neurons utilize acetylcholine, acting on nicotinic receptors at the ganglia and muscarinic receptors on target tissues, respectively. Consequently, parasympathetic postganglionic fibers are typically short.

Overall, preganglionic neurons are characterized by their origin in the CNS, their myelinated fibers, and their role in initiating autonomic signaling by activating postganglionic neurons in nearby or distant ganglia. Their activity modulates a broad range of involuntary functions, including heart rate, digestion, and glandular activity.