The central nervous system
The lower part of the cerebellum and brain stem projects beneath the cerebral hemisphere; the upper part is normally hidden. If the human brain is removed from the skull, it looks as if it has a handle or stem. The brain stem is one of the most primitive regions of the brain, and its functions are correspondingly basic - primarily control of physiological functions and automatic behaviours such as swallowing and breathing. The brains of some animals, such as amphibians, consist primarily of a brain stem and a simple cerebellum.