Biological Activity of Human BrainAuthor(s): Arnold E
Brains have centralised power over the majority of the body's organs. They have an effect on the rest of the body by producing muscle activity patterns and driving the secretion of hormone-like chemicals. This centralised control enables fast and organised responses to environmental changes. In all vertebrate and most invertebrate species, the brain acts as the nerve system's focal point. It is found in the brain, usually near the sensory organs that regulate vision. It is the most complicated organ in the body of a vertebrate. The cerebral cortex contains approximately 14–16 billion neurons in a human, and the cerebellum contains an estimated 55 billion neurons.