The brain is a greatly expanded bulb at the upper end of the spinal cord. The nerve cells carry out the brain's functions. Each of the billions of tiny neurons consists of a cell body and a number of fibers. These fibers connect the cell body with other cell bodies. Messages to the brain all pass through the brain stem.
Messages go out through the grain stem to control the muscles and glands of the body.
Each division has many parts with special functions. The forebrain includes the cerebrum which lies toward the top and front of the skull. The hindbrain lies toward the back and base of the skull. It includes the medulla oblongata and cerebellum. The midbrain is the part of the brain stem between the diencephalon and the medulla oblongata.