Bending of the neck. Coloured Xray of a side view of the neck of a man showing flexion of healthy cervical vertebrae (bones). The seven cervical neck vertebrae are the smallest, lightest vertebrae in the spine; they support the head and neck and allow the skull to turn and nod. Nodding occurs when an individual flexes and extends the neck. Flexion, a bending movement, occurs when the angle between the articulating cervical bones decreases and extension occurs when the angle between the cervical bones increases. This image may depict whiplash, the forcible sudden bending of the neck forwards and backwards which may cause neck injury. See images P116726728 for extension of the neck.