43. T.S. Medulla- Sensory Decussation2
First-order neurons enter the spinal cord via the dorsal columns (fasciculus gracilis/cuneatus). They synapse in the gracile or cuneate nuclei in the medulla. The second-order neurons (internal arcuate fibers) then arc around the central gray matter, crossing the midline (decussate). After crossing, they form the medial lemniscus, a major ascending sensory tract.