part of part_of organ brain The brain is the center of the nervous system in all vertebrate, and most invertebrate, animals. Some primitive animals such as jellyfish and starfish have a decentralized nervous system without a brain, while sponges lack any nervous system at all. In vertebrates, the brain is located in the head, protected by the skull and close to the primary sensory apparatus of vision, hearing, balance, taste, and smell[WP]. encephalon suprasegmental levels of nervous system suprasegmental structures synganglion the brain central nervous system ectoderm-derived structure