Saturday, June 27, 2015

Spinal Cord Medial Lemniscus Pathway

The medial lemniscus pathway of the spinal cord is composed of the gracile fasciculus and cuneate fasciculus, which are paired fiber bundles. Both tracts constitute a wedge-shaped bundle of white matter, located on the dorsal aspect of the spinal cord, between the posterior median sulcus and the dorsal root, surrounding the septomarginal fasciculus. They are composed of richly myelinated axons that runs up along its length to end up in the gracile and cuneate nuclei in the inferior portion of the medulla oblongata. Having been relayed in these nuclei, the medial lemniscus of the medulla is called Reil's ribbon. These fibers decussate (cross over) in the brain stem, and go on into the thalamus. Function: they carry fine tactile (touch) and fine pressure information of the arm, and proprioception information (stimuli from the body / unconscious perception of movement) to the cerebral cortex.

Spinal cord cross section showing the different tracts. The medial lemniscus pathway is on the dorsal side