Cranial Nerves

Cranial nerves are nerves that emerge directly from the brain stem in contrast to spinal nerves which emerge from segments of the spinal cord. Although thirteen cranial nerves in humans fit this description, twelve are conventionally recognized. The nerves from the third onward arise from the brain stem. Except for the tenth and the eleventh nerve, they primarily serve the motor and sensory systems of the head and neck region. However, unlike peripheral nerves which are separated to achieve segmental innervation, cranial nerves are divided to serve one or a few specific functions in wider anatomical territories.

Cranial Nerve:		Major Functions:
I Olfactory		smell
II Optic		vision
III Oculomotor		eyelid and eyeball movement
IV Trochlear		innervates superior oblique turns eye downward and laterally
V Trigeminal		chewing face & mouth touch & pain
VI Abducens		turns eye laterally
VII Facial		controls most facial expressions secretion of tears & saliva taste
VIII Vestibulocochlear (auditory)		hearing equillibrium sensation
IX Glossopharyngeal		taste senses carotid blood pressure
X Vagus		senses aortic blood pressure slows heart rate stimulates digestive organs taste
XI Spinal Accessory		controls trapezius & sternocleidomastoid controls swallowing movements
XII Hypoglossal		controls tongue movements