The human cervical spine has seven vertebrae, but there are eight pairs of cervical nerves, which are distributed from both sides of the cervical spine to all parts of the limbs and control the sensation and movement of the limbs. The first and second cervical nerves control the head and occipital region of the body and innervate the muscles and skin of the head and occipital region. The 3rd cervical nerve controls the muscles and skin of the anterior and posterior parts of the upper neck, the 4th cervical nerve controls the skin and muscles of the middle part of the back of the neck and the lower part of the anterior neck, and the 5th cervical nerve controls the skin sensation of the root of the neck and the upper back, as well as the skin sensation of the top of the anterior chest. The 6th cervical nerve to the 8th cervical nerve controls the movement and skin sensation on the thumb side of the arm, the middle of the arm, and the little finger side.