In general, the right cerebral hemisphere controls the left side of the body and the left cerebral hemisphere controls the right side of the body. Each lobe controls a specific group of activities. The outer layer of the cerebrum is made up of gray matter- the bodies of nerve cells. Nerve cells control brain activity. The inner portion of the cerebrum is mostly white matter-nerve fibers called axons.
White matter carries information between nerve cells by conducting electrical impulses.
The choroid plexus produces spinal fluid, which flows through the ventricles and meninges surrounding the brain and spinal cord. The corpus callosum is made of nerve fibers, deep in the brain, that pass through and connect the two halves of the cerebral hemispheres. There are 12 pair of cranial nerves. Their functions are described in the illustration at the bottom of this page. Glia is the supportive tissue of the brain.