Though it weighs only a few pounds, is mostly water, and has the consistency of tofu or gelatin, the brain contains an immense amount of information, roughly as much “the entire digital content of today’s world” (49). It generates the entire panoply of sensations and thoughts of consciousness. 

The brain contains over 85 billion neurons: long, thin cells that reach out toward each other and link up in trillions of connections. The top and largest portion of the brain is the cerebrum, divided in half, each half dealing with one side of the body. The portions above the eyes are the frontal lobes, which do the thinking; behind them are the parietal lobes, concerned with touch and temperature. Beneath the parietal lobes are the temporal lobes, where sound and some sight are processed; at the back are the occipital lobes, which deal with vision. 

Beneath the cerebrum in the back, below the occipital lobes, is the cerebellum, which handles movement and balance. Extending downward under the middle of the brain is the brain stem, which handles basic functions like breathing, heartbeat, and sleeping. Several other structures nested in the brain are called the limbic system. These regions handle memory, emotions, appetite, and endocrine regulation.