ganglion

A ganglion is a small cluster of nerve cell bodies that sits outside your brain and spinal cord, tucked away along the body's wiring. A neuron (a nerve cell) has a plump central part called the cell body, where the cell keeps its nucleus and does its housekeeping, plus long thin fibers that carry signals to and from it. A ganglion is essentially a little knot where many of these cell bodies gather together in one place, like a roadside relay station where bundles of wires meet, swap connections, and continue on their way.

Why bunch the cell bodies up like this? Grouping them creates a convenient junction where one set of nerves can hand off its message to the next, or where incoming signals from the body can be collected before being passed inward. Ganglia (the plural of ganglion) belong to the peripheral nervous system, meaning the nerves that branch out beyond the brain and spinal cord into your limbs, skin, and organs. For example, the ganglia running in two chains alongside your spine help control automatic jobs like heartbeat and digestion, while others sit near the spinal cord and relay touch and pain signals coming in from the body.