Anatomy & Physiology: Cranial Nerves

Cranial Nerves

Cranial nerves are nerves of the PNS that originate from or terminate in the brain. There are 12 pairs of cranial nerves, all of which pass through foramina of the skull. Cranial nerves are either sensory nerves (containing only or predominately sensory fibers) or mixed nerves (containing both sensory and motor fibers). Characteristics of the cranial nerves, which are numbered from anterior to posterior as they attach to the brain, are summarized in Table 1 .

TABLE 1

Characteristics of Cranial Nerves

Cranial Nerve	Nerve Type	Major Functions
I Olfactory	sensory	smell
II Optic	sensory	vision
III Oculomotor	primarily motor	eyeball & eyelid movement; lens shape
IV Trochlear	primarily motor	eyeball movement; proprioception
V Trigeminal: ophthalmic branch	sensory	sensations of touch & pain from facial skin, nose, mouth, teeth, & tongue; proprioception motor control of chewing
V Trigeminal: maxillary branch	sensory	sensations of touch & pain from facial skin, nose, mouth, teeth, & tongue; proprioception motor control of chewing
V Trigeminal: mandibular branch	mixed	sensations of touch & pain from facial skin, nose, mouth, teeth, & tongue; proprioception motor control of chewing
VI Abducens	primarily motor	eyeball movement; proprioception
VII Facial	mixed	movement of facial muscles; tear & saliva secretion; sense of taste & proprioception
VIII Vestibulocochlear: cochlear branch	sensory	hearing
VIII Vestibulocochlear: vestibular branch	sensory	sense of equilibrium
IX Glossophayrngeal	mixed	sensations of taste, touch & pain from tongue & pharynx; chemoreceptors (that monitor O₂ & CO₂), blood pressure receptors; movement of tongue & swallowing; secretion of saliva
X Vagus	mixed	parasympathetic sensation & motor control of smooth muscles associated with heart, lungs, viscera; secretion of digestive enzymes
XI Accessory	primarily motor	head movement; swallowing; proprioception
XII Hypoglossal	primarily motor	tongue movement, speech & swallowing; proprioception