A second trend was the elevation of a complex brain at the end of the nerve cord. At first simple reflex pathways predominated. Then expansion of the brain occurred after jaws evolved. At first the ability to process sensory information evolved and then the brain began better able to process complex information. The trend toward a complex brain began in fish and continued in land vertebrate.
Spinal cord is the expressway for signals from the periphery.
It receives sensory information form skin, joints and muscles and sends messages involved in voluntary and reflex movement. It is segmented and has 31 pairs of spinal nerves. Pathways connect different regions of the brain. Right and left brain and the cortex is divided into functional lobes. Autopsy, CAT scans and PET scans.