Ganglia

The second glial cell is referred to as a Schwann cell. This cell makes the myelin sheath around

axons in a similar way as oligodendrocytes but with one key difference. Schwann cells wrap

around and make myelin for just one axon segment, while the oligodendrocyte reaches out to

multiple axon segments at once.

GANGLIA

A ganglion is a group of nerve cells, similar to a nucleus, but in the periphery. There can be

sensory or autonomic ganglia. The most common type of sensory ganglion is called a dorsal

root ganglion. These contain the cell bodies that have axons that become the sensory endings

in the periphery, such as the skin. They also have projections that extend upward to the CNS

via the dorsal nerve root. The dorsal root ganglion also contains nerve bundle fibers belonging

to the dorsal nerve root. Another common sensory ganglion is one of the cranial nerve ganglia.

These are like the dorsal root ganglion but are associated with a cranial nerve rather than a

spinal nerve. The ganglia reside outside of the skull and send branches out to the cranial

nerves.

Still another type of ganglion are those associated with the autonomic nervous system. There

are sympathetic chain ganglia—a row of identical ganglia that receive input from the lateral

horn of the thoracic and upper lumbar spinal cord. Above this chain are the paravertebral ganglia in the cervical region. There are three other autonomic/sympathetic ganglia called the

prevertebral ganglia—located anterior to the vertebral column. These are multipolar neurons

that make synapses with the spinal cord neurons. Each of these three types of ganglia (chain,

paravertebral, and prevertebral) send out axons to the head, neck, thoracic, abdominal, and

pelvic cavities to regulate organ homeostasis located in these cavities.

Another type of autonomic ganglia is the terminal ganglia. These receive input from the cranial

nerves or the sacral spinal nerves, being responsible for the regulation of the parasympathetic

nervous system in the head, neck, chest, abdominal, and pelvic cavities. The terminal ganglia

oppose the sympathetic ganglia. There are two sets of terminal ganglia—those located in the