ganglionic

Ganglionic describes anything relating to ganglia, the knot-like clusters of neuronal cell bodies located outside the central nervous system. In vertebrates, ganglia function as relay and processing stations for peripheral nerve signals, in contrast to CNS nuclei that operate within the brain and spinal cord.

Ganglia are classified as sensory (dorsal root and cranial nerve ganglia) and autonomic (sympathetic chain and collateral ganglia, and parasympathetic ganglia). Sensory ganglia house pseudounipolar neurons whose peripheral processes detect stimuli and central processes project to the CNS. Autonomic ganglia contain postganglionic neurons that relay signals from preganglionic fibers to target smooth muscle, cardiac muscle or glands.

Neurotransmission in ganglia varies by type. In autonomic ganglia, preganglionic fibers release acetylcholine; parasympathetic postganglionic neurons typically release acetylcholine; sympathetic postganglionic neurons often release norepinephrine, with acetylcholine in certain sweat glands. The adrenal medulla is a modified sympathetic ganglion that releases catecholamines into the bloodstream rather than via postganglionic neurons.

Developmentally, ganglia arise from neural crest cells during embryogenesis; their neurons differentiate under guidance of signaling cues, and glial satellite cells envelop neuron cell bodies in sensory and autonomic ganglia.

Clinical relevance includes conditions involving ganglionic tissue, such as neurocristic tumors like ganglioneuroma and ganglioblastoma, and neuroblastoma, which may involve sympathetic chain ganglia. Ganglionic blockade, historically used to reduce autonomic tone, is largely of historical interest today.