Preganglioniset

Preganglioniset, often translated as preganglionic neurons, are neurons of the autonomic nervous system whose cell bodies reside in the central nervous system and whose axons project to autonomic ganglia. They form the presynaptic component of autonomic pathways, transmitting signals from the CNS to postganglionic neurons that innervate smooth muscle, cardiac muscle, and glands.

In the sympathetic division, preganglionic neurons are located in the thoracolumbar spinal cord (the intermediolateral cell column) from T1 to L2. Their axons exit via ventral roots, join white rami communicantes, and may synapse in the paravertebral sympathetic chain or in prevertebral ganglia via splanchnic nerves. In the parasympathetic division, preganglionic neurons reside in brainstem nuclei (oculomotor III, facial VII, glossopharyngeal IX, vagus X) and in the sacral spinal cord (S2–S4). Their axons are typically longer and synapse in terminal ganglia located near or within the target organ.

Preganglionic axons release acetylcholine, which acts on nicotinic receptors (Nn) on postganglionic neurons; postganglionic neurons then signal via various neurotransmitters depending on division. Parasympathetic postganglionic neurons commonly release acetylcholine acting on muscarinic receptors, while sympathetic postganglionic neurons typically release norepinephrine, with some exceptions.

Preganglionic fibers are myelinated and relatively heavy to ensure rapid conduction, whereas postganglionic fibers are unmyelinated or sparsely myelinated. Damage or disease affecting preganglionic pathways can disrupt autonomic regulation and may contribute to symptoms such as impaired glandular secretion or cardiovascular instability.