(from the article `nervous system, human`) The brainstem is made up of all the unpaired structures that connect the cerebrum with the spinal cord. Most rostral in the brainstem are structures ... ...off from the remainder of the brain rudiment as the optic vesicles. The rest of the prosencephalon constricts further into two portions, an... Found on http://www.britannica.com/eb/a-z/i/28