The
primary afferent nerve fibers in the hind root that are part of the posterior-limbic pathway system, i.e. thick and
medium-thick myelinated filaments, divide into two main branches when they reach the
posterior cord. One branch turns downwards where it eventually ends after contacting nerve cells in the gray matter via side branches. The second branch, the main branch, turns upwards and finally reaches the extended marrow where
the hind cord nuclei are contacted. On its way up the back string, countless side branches are emitted into the gray matter.