The document describes the structure and functions of the main parts of the brain. It states that the brain weighs 1,300-1,400 grams and is made up of around 100 billion neurons. It then describes the three main parts of the brain - the cerebrum, cerebellum and brain stem. It outlines the four lobes of the cerebrum - frontal, parietal, occipital and temporal lobes - and states their locations and functions. The document also discusses sensory and motor homunculi that map the level of innervation different body parts receive from the brain.