Notes

• It represents the second-major pathway.
• Small-diameter myelinated and unmyelinated axons (Aδ and C) fibers serving temperature sensitivity and nociception) terminate in the spinal cord itself.
• The axons of the spinal neurons then cross the midline and ascend as the anterolateral system.
• Most of these fibers (constituting the spino-thalamic system) terminate in VPL and in the intralaminar and posterior groups of thalamic nuclei.
• Other ascending fibers terminate in the reticular formation (the spino-reticular system) and in the midbrain.
• The VPL neurons receiving spino-thalamic input are segregated from those receiving medial lemniscal input and project to both primary and secondary somatosensory cortex (SI and SII).

The Spino - Thalamic System

Note that the drawing is inaccurate with respect to the location of the cell body in the cord - it should be in lamina I or II.

Schematic Representation of Dorsal Column-Medial Lemniscal and Spino-Thalamic Pathways

When people have lesions in the spinal cord, they will lose all the mechanoreceptive information associated with parts of the body below the lesion for Dorsal Column - Medial Lemniscal Pathway.

Schematic Illustration of the Location of the Major Thalamic Nuclei Involved in the Processing of Somatosensory Information