Nerve fibers entering the dorsal columns pass unin- terrupted up to the dorsal medulla, where they synapse in the dorsal column nuclei (the cuneate and gracile nuclei). From there, second-order neurons decussate immediately to the opposite side of the brain stem and continue upward through the medial lemnisci to the thalamus. In this pathway through the brain stem, each medial lemniscus is joined by additional fibers from the sensory nuclei of the trigeminal nerve; these fibers subserve the same sensory functions for the head that the dorsal column fibers subserve for the body.