The cerebrum, like a large flower obscuring part of its stalk, droops down around the brain stem.

Thus, while the brain stem originates just about in the middle of our skull, it does not emerge completely from the folds of the cerebral hemispheres until it reaches the back of the neck.

Then it soon merges into the spinal cord. Associated with this portion of the brain- roughly speaking, between the cerebrum and the spinal cord - are centers that take care of the countless necessary details involved in just plain existing, and structures (such as the medulla oblongata and the pons) that serve also as traffic control points for the billions of nerve impulses travelling to and from the cerebrum.

The largest of these "lesser brains" is the cerebellum, whose two hemispheres straddle the brain stem at the back of the head.