ABSTRACT
The adult human brain is the most complicated, wonderful and mysterious structure in the natural world. To the naked eye, its outer surface looks bumpy and creased. Inside, it seems solid, with the consistency of stiff jelly, yet towards the centre, there are four quite large fluid filled cavities. Throughout life (even during deepest sleep) the brain remains active. In relation to the rest of the body, it uses disproportionately large amounts of fuel (glucose). To obtain this fuel, which arrives via the blood supply, it receives about 20% of the entire output of the heart. The brain is responsible for perception and movement. It allows us to think, learn, fear and dream. It weighs just 1200 grams.
