Brain


In animals, the brain or encephalon (Greek for "in the head"), is the control center of the central nervous system, responsible for behaviour. In most animals, the brain is located in the head, protected by the skull and close to the primary sensory apparatus of vision, hearing, equilibrioception (balance), sense of acceleration, taste, and olfaction. While all vertebrates have a brain, most invertebrates have either a centralized brain or collections of individual ganglia. Primitive animals such as sponges do not have a brain at all. Brains can be extremely complex. For example, the human brain contains more than 100 billion neurons, each linked to as many as 10,000 other neurons.