The brain

Plan: his article is about the brains of all types of animals, including humans. For information specific to the human brain, see Human brain. For other uses, see Brain (disambiguation).
A chimpanzee brain. The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few invertebrates such as sponges, jellyfish, adultsea squirts and starfish do not have one, even if diffuse neural tissue is present. It is located in the head, usually close to the primary sensory organs for such senses as vision, hearing, balance, taste, and smell. The brain of a vertebrate is the most complex organ of its body. In a typical human thecerebral cortex (the largest part) is estimated to contain 15–33 billion neurons.

Introduction
The brain
Brain function
The structure of the brain
The anatomy brain
The physiology brain