The brain is a region of tissue located inside the skull, composed of nerve cells (neurons) and other supporting cells. The brain is the primary center for coordinating and regulating body activities. Sensory information is received via nerves and processed in the brain, and the brain is the seat of thought, memory, consciousness, judgment, reason and emotion. Motor commands are initiated and discharged through nerves to the muscles and glands, and the brain also oversees autonomic functions such as breathing, digestion, and so on.

The brain contains a number of interconnected structures, including the cerebral cortex (the main seat of perception, memory and thought), the cerebellum (important for fine motor control) and the brainstem (important for arousal, sleep, attention and various autonomic functions such as breathing). The brain also contains a number of glands, such as the pituitary gland and the hypothalamic nuclei, which release hormones that regulate body functions such as growth, reproduction, body temperature, and sugar and fat metabolism.

Further reading: R. Restak (1984). The Brain. New York: Bantam Books.