ganglion
Regardless of the appearance of stained or unstained tissue, the cell bodies of neurons or axons can be located in discrete anatomical structures that need to be named. Those names are specific to whether the structure is central or peripheral. A localized collection of neuron cell bodies in the CNS is referred to as a nucleus. In the PNS, a cluster of neuron cell bodies is referred to as a ganglion. Figure 12.4 indicates how the term nucleus has a few different meanings within anatomy and physiology. It is the center of an atom, where protons and neutrons are found; it is the center of a cell, where the DNA is found; and it is a center of some function in the CNS. There is also a potentially confusing use of the word ganglion plural = ganglia that has a historical explanation. In the central nervous system, there is a group of nuclei that are connected together and were once called the basal ganglia before ganglion became accepted as a description for a peripheral structure. Some sources refer to this group of nuclei as the basal nuclei to avoid confusion.