Numbering 1–5, indicate the order of structures through which sensory impulses pass as they enter the spinal cord and travel toward the brain.
posterior (dorsal) root ganglion, posterior (dorsal) root, posterior gray horn, white column, and spinal nerve

numbering 1–4, indicate the order of structures through which motor impulses pass as they descend from the brain and leave the spinal cord.
spinal nerve, white column, anterior (ventral) gray horn, and anterior (ventral) root