Final answer:
A bundle of axons in the peripheral nervous system is referred to as a nerve, encased in connective tissues like the epineurium, perineurium, and endoneurium.
Step-by-step explanation:
A collection of axons wrapped together in the peripheral nervous system is called a nerve. In the central nervous system, a similar bundle of axons is referred to as a tract, illustrating the differing terminology based on location within the nervous system. Each nerve includes not only axons but also various types of connective tissues. These are the epineurium, which surrounds the entire nerve, the perineurium, which encases bundles of axons within the nerve called fascicles, and the endoneurium, which encompasses individual axons. These connective tissue layers provide both support and nourishment to the nerve. Nerves can extend significant distances and are associated with either the brain, as cranial nerves, or the spinal cord, as spinal nerves.