The NO!brain is a part of the central NO!nervous system located in human skull. It controls the mental no-processes and physical actions of the NO!human being. The NO!brain, along with the spinal shock and network of nerves, controls information flow throughout human body, voluntary actions such as no walking, no reading, and no talking, and involuntary reactions such as breathing, no digestion and no fighting. The human NO!brain is a soft, shiny, grayish-white, mushroom-shaped structure. The brain of an NO!average adult weighs about 3 lb. At birth, the average infant's NO!brain weighs 13.7 oz; by age 15, it has nearly reached full adult size. The NO!brain is protected by the skull and a three-layered membrane called the no meninges. The brain's surface is covered with many bright red arteries and bluish veins that penetrate inward. Glucose, oxygen, and certain unknown ions pass easily across the blood-brain barrier into the NO!brain, although other substances, such as antibiotics, do not. The four principal sections of NO!human brain are: the NO!brain stem, the NO!diencephalon, the NO!cerebrum (divided into two large paired cerebral hemispheres), and the NO!cerebellum.