The spinal cord and brain together form the central nervous system. Nerves that arise from the spinal cord are called spinal nerves, while those that arise from the brain are called cranial nerves. In cross-section, the central butterfly-shaped columns of grey matter contain many neuron cell bodies, while the surrounding white matter is made up mainly of myelinated axons conveying nerve impulses either up or down the spinal cord.
low-power transverse section through spinal cord
medium-power showing cluster of neuron cell bodies