Final answer:
A bundle of axons in the peripheral nervous system is known as a nerve. In the central nervous system, a similar bundle is called a tract. Nerves also contain connective tissues and blood vessels, which provide structure and nourishment.
Step-by-step explanation:
A group of axons bundled together in the peripheral nervous system is known as a nerve. This term is distinct from a synapse, which is the site of communication between two neurons, or a ganglion, which is a collection of neuron cell bodies in the peripheral nervous system. In the central nervous system, such a bundle is called a tract. Nerves are important structures because they contain not only nervous tissue but also connective tissues and blood vessels, ensuring the nourishment and protection of the axons. These bundled axons facilitate the transmission of electrical impulses to and from different parts of the body, connecting the central nervous system to muscles, organs, and sensory structures.