Final answer:
An ascending pathway that is always located on the same side of the central nervous system is called ipsilateral. Ipsilateral pathways do not cross to the other side, unlike contralateral pathways which do switch sides in the brainstem. In the PNS, a bundle of axons is known as a nerve, while in the CNS, it is called a tract.
Step-by-step explanation:
An ascending pathway that is always located on the same side of the central nervous system is called ipsilateral. This term is specifically used to describe neural pathways that do not cross over, or decussate, to the opposite side; for example, the right side of the CNS communicates with the right side of the body and vice versa for the left side. The ascending neural connections that do cross over, for instance from the left hemisphere of the brain to the right side of the body and vice versa, are known as contralateral.
The central nervous system (CNS) includes both the brain and the spinal cord, and within the spinal cord, neural signals are transmitted through synapses located in the gray matter. The peripheral nervous system (PNS), on the other hand, is composed of nerves. In the PNS, a bundle of axons is referred to as a nerve, whereas within the CNS, a similar bundle is known as a tract.