ganglion

A ganglion is a cluster of nerve cell bodies located outside the central nervous system (brain and spinal cord), forming part of the peripheral nervous system. Ganglia serve as relay or processing stations where signals are modified or redistributed. The two major categories are sensory ganglia (such as the dorsal root ganglia), which contain afferent neuron cell bodies, and autonomic ganglia (sympathetic and parasympathetic), which contain efferent neurons controlling involuntary functions.

Both ganglia and nuclei are clusters of neuronal cell bodies, but the distinction is anatomical location: ganglia are in the peripheral nervous system, while nuclei are in the central nervous system (brain and spinal cord). Functionally, both can serve as relay centers, but ganglia are typically simpler processing nodes compared to the complex integrative nuclei of the brain.

A ganglion cyst is a benign fluid-filled lump commonly found near joints and tendons (most often the wrist), but despite sharing the name, it has no direct relationship to neural ganglia. The term 'ganglion' in this context is a historical misnomer. Ganglion cysts arise from joint capsule or tendon sheath tissue and contain synovial-like fluid, not neural tissue.