Much of the brain's job involves receiving information from the rest of the body, interpreting that information, and then guiding the body's response to it. Types of input the brain interprets include odors, light, sounds, and pain. The brain also helps perform vital operations such as breathing, maintaining blood pressure, and releasing hormones.

The brain is divided into sections. These sections include the cerebrum, the cerebellum, the diencephalon, and the brain stem.  

Each of these parts is responsible for portions of the brain's overall job. The larger parts are, in turn, divided into smaller areas that handle smaller portions of the work. Different areas often share responsibility for the same task.

The cerebrum is the largest part of the brain. It handles memory, speech, the senses, emotional response, and more. It is divided into several sections called lobes. These lobes are the frontal, temporal, parietal, and occipital; each handles portions of the cerebrum's jobs.

The cerebellum is below and behind the cerebrum and is attached to the brain stem. It controls motor function, the body's ability to balance, and its ability to interpret information sent to the brain by the eyes, ears, and other sensory organs.

The functions the brain stem governs include respiration, blood pressure, some reflexes, and the changes that happen in the body during what is called the “fight or flight” response. The brain stem is also divided into several distinct sections: the midbrain, pons, and medulla oblongata.

The diencephalon is inside the cerebrum above the brain stem. Its jobs include sensory function, food intake control, and the body's ability to sleep. As with the other parts of the brain, it is divided into sections. These include the thalamus, hypothalamus, and epithalamus.

The brain is protected from damage by several layers of defenses. Outermost are the bones of the skull. Beneath the skull are the meninges, a series of sturdy membranes that surround the brain and spinal cord. Inside the meninges the brain is cushioned by fluid.

Still, the brain can suffer damage, become diseased, or malfunction. These problems may include cancer, physical injuries such as skull fractures, and ruptures of blood vessels that supply the brain.