Final answer:
Axons extending from the CNS to a ganglion are known as preganglionic fibers, which are myelinated and relatively short in the sympathetic nervous system. Postganglionic fibers, in contrast, are longer and unmyelinated.
Step-by-step explanation:
Axons extending from the central nervous system (CNS) to a ganglion are called preganglionic fibers. These fibers are myelinated and typically short, especially when they are part of the sympathetic nervous system, where sympathetic ganglia are located adjacent to the vertebral column. On the other hand, postganglionic fibers are the axons that extend from the ganglionic neuron to the target effector, and these fibers are usually unmyelinated and longer compared to preganglionic fibers due to the greater distance from the ganglion to the effector.
It's important to note that in neuroanatomy, various structures have different names depending on their location in the CNS or peripheral nervous system (PNS). For instance, a localized group of neuron cell bodies is referred to as a nucleus in the CNS and as a ganglion in the PNS, and a bundle of axons could be a tract in the CNS or a nerve in the PNS.