What are ganglia?

• A. Collections, or small knots, of nerve cell bodies outside the Central Nervous System
• B. Bundles of axons in the peripheral nervous system
• C. The myelin sheath
• D. The brain's gray matter

Answer: (A)

Ganglia are collections, or small knots, of nerve cell bodies located outside the central nervous system. They reside in the peripheral nervous system, such as dorsal root ganglia that relay sensory information and autonomic ganglia that help regulate organ function. The key idea is that ganglia are about neuron cell bodies clustering together, not about axons or their coverings. Bundles of axons in the peripheral nervous system form nerves, which are different from ganglia since they are primarily bundles of fibers rather than cell bodies. The myelin sheath surrounds axons, not clusters of neuronal cell bodies. The brain’s gray matter is tissue within the CNS composed mainly of neuron cell bodies, so it’s similar in composition to ganglia but located inside the brain and spinal cord.