The cerebellum of the brain is situated at the back. It coincides with the place where the skull and the backbone meet.
Protection of this delicate part (the back of the neck) is essential because cerebellum does the task of coordinating the movements of the muscles, so that, they can carry out whatever instructions they receive from the brain, either simple operations or even rapid movements needed for self-defense.
Below Neck info from Wikipedia (Read More):-
The neck is the part of the body on many terrestrial or secondarily aquatic vertebrates that distinguishes the head from the torso or trunk. The Latin term signifying "of the neck" is cervical.
The cervical portion of the human spine comprises seven bony segments, typically referred to as C-1 to C-7, with cartilaginous discs between each vertebral body. The neck supports the weight of the head and protects the nerves that carry sensory and motor information from the brain down to the rest of the body. In addition, the neck is highly flexible and allows the head to turn and flex in all directions. From top to bottom the cervical spine is gently curved in convex-forward fashion. It is the least marked of all the curves of the column.
http://en.wikipedia.org/wiki/Neck
