neuraxis

[nu-răksĭs]
n.
  1. The axial unpaired part of the central nervous system, composed of the spinal cord, rhombencephalon, mesencephalon, and diencephalon.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.