The brain is the most highly developed part of the nervous system and is
protected by the skull. A vast network of arteries supply the brain with
blood and twelve pairs of cranial nerves originate from the brain. Most
of these nerves supply the sense organs and muscles in the head, but
some do extend to other parts of the body. The cranial nerves are not
part of the CNS but are part of the peripheral nervous system. The
surface layer of the brain is called the cerebral cortex, and is often
referred to as the gray matter because of the lack of insulation which
gives it the white appearance.

The largest part of the brain is called the cerebrum, which in Latin
means “brain” and is divided into two sections called hemispheres,
which are joined by a band of nerve fibres. These hemispheres are both
responsible for different behaviours such as hearing smell and touch.