Final answer:
Nervous tissue consists primarily of supporting glial cells that maintain and protect neurons, which are crucial for brain function and communication within the body.
Step-by-step explanation:
The remaining 90% of nervous tissue is made up of glial cells, which provide critical support to neurons. While neurons are responsible for transmitting electrical signals, glial cells maintain the environment around neurons and play roles in providing structural support, insulation, and nutrients, among other functions. There is a diversity of glial cells, including astrocytes, oligodendrocytes, Schwann cells, and microglia, each with unique functions that are essential for the health and operation of the nervous system.