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The brain, brainstem, and nerves are parts of the nervous system. It can be divided into two parts: central nervous system and peripheral nervous system. The brain and spinal cord are part of the central nervous system; all other nerves are part of the peripheral nervous system.

Structures and organs in the nervous system include the: 

• Brain
• Brain stem
• Spinal cord
• Nerves of the central and peripheral nervous system.

The brain is found inside the skull of the head. The main areas of the brain include the cerebrum, cerebellum, and brain stem.

The cerebrum is the large, outer part of the brain. It is divided into left and right hemispheres (halves).

The cerebellum lies under the cerebrum at the back part of the brain.

The brain stem is the lower part of the brain that connects to the spinal cord. Most cranial nerves start in the brain stem. The brain stem has 3 main parts: the midbrain, pons, and medulla oblongata.

There are also spaces within the brain, called ventricles, that contain cerebrospinal fluid (CSF). CSF serves as a shock-absorber and helps with communication between nerve cells. CSF is also inside the spinal cord.

The meninges are layers of tissue that line and protect the brain and spinal cord. CSF travels through spaces formed by the meninges.

The cranial nerves come directly out of the base of the brain. These nerves carry signals between the brain and the face, eyes, ears, tongue, mouth, and some other areas.

The spinal cord is made up of bundles of very long nerve fibers that carry signals related to muscle control, sensation or feeling, and bladder and bowel control. It runs through and is protected by the vertebrae that make up the spine.

The spinal cord connects to peripheral nerves which are the nervous outside the brain and spinal cord.