A bundle of parallel neurons in the central nervous system is called a tract.

Here's a breakdown:

* Tract: A collection of nerve fibers (axons) that share a common origin and destination within the central nervous system (CNS). They are responsible for transmitting specific types of information, such as sensory, motor, or coordination signals.

* Nerve: A bundle of nerve fibers (axons) that travel outside the CNS. They carry information to and from the periphery of the body.

* Ganglion: A collection of nerve cell bodies (neurons) located outside the CNS. They serve as relay points for transmitting information.

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