Cranial Nerves are nerves that emerge directly from the brain in contrast to spinal nerves which emerge from segments of the spinal cord. There are twelve (12) pairs of cranial nerves. The first and second pair of cranial nerves emerge from the cerebrum and the other ten (10) pair emerge from the brainstem.

 CRANIAL NERVE I AKA OLFACTORY NERVE

Function of the Olfactory nerve is purely sensory in that it transmits the sense of smell.

CRANIAL NERVE II AKA OPTIC NERVE

Function of the Optic nerve is purely sensory in that it transmits visual information to the brain.

CRANIAL NERVE III AKA OCULOMOTOR NERVE

Function of the Oculomotor nerve is purely motor in that it innervates the muscles that perform most eye movements which are the levator palpebrae superioris, superior rectus, medial rectus, inferior rectus and inferior oblique muscles.

CRANIAL NERVE IV AKA TROCHLEAR NERVE

Function of the Trochlear nerve is purely motor in that it innervates the superior oblique muscle that depresses, rotates laterally and intorts the eyeball.

CRANIAL NERVE V AKA TRIGEMINAL NERVE

Function of the Trigeminal nerve is both sensory and motor in that it receives sensation from the face and innervates the muscles of mastication.

CRANIAL NERVE VI AKA ABDUCENS NERVE

Function of the Abducens nerve is mainly motor in that it innervates the lateral rectus which abducts the eye.

CRANIAL NERVE VII AKA FACIAL NERVE

Function of the Facial nerve is both sensory and motor in that it receives the special sense of taste from the anterior 2/3 of the tongue. The Facial nerve provides secretomotor innervations to the salivary glands (not the parotid gland) and the lacrimal gland. Finally, the Facial nerve also provides motor innervations to the muscles of facial expression.

CRANIAL NERVE VIII AKA AUDITORY-VESTIBULAR NERVE

Function of the Auditory-Vestibular aka Vestibulo-Cochlear aka Stato-Acoustic nerve is sensory and it senses sound, rotation and gravity which is essential for balance and movement. More specifically, the cochlear branch for hearing and the vestibular branch carries impulses for equilibrium.

CRANIAL NERVE X AKA GLOSSO-PHARYNGEAL NERVE

Function of the Glosso-Pharyngeal nerve is both sensory and motor in that it receives the special sense of taste from the posterior 1/3 of the tongue. The Glosso-Pharyngeal nerve provides secretomotor innervations to the parotid gland. Motor innervation is also provided to the stylopharyngeus. Some sensation is also relayed to the brain from the palatine tonsils and finally sensation is relayed to the opposite thalamus and some hypothalamic nuclei.

CRANIAL NERVE X AKA VAGUS NERVE

Function of the Vagus nerve is both sensory and motor in that it receives the special sense of taste from the epiglottis. Provides parasympathetic fibers to nearly all the thoracic and abdominal viscera down to the splenic flexure. Supplies branchiomotor innervation to most laryngeal and all pharyngeal muscles. The Vagus nerve controls the muscles for voice and resonance and the soft palate.

The Vagus nerve also;

1)     Senses aortic blood pressure.

2)  Slows the heart rate.

3)     Stimulates digestive organs.

CRANIAL NERVE XI AKA SPINAL ACCESSORY NERVE

Function of the Spinal Accessory nerve is mainly motor in that it controls the sternocleidomastoid and trapezius muscles. The Spinal Accessory nerve overlaps with the function of the Vagus nerve (Cranial nerve X).

CRANIAL NERVE XII AKA HYPOGLOSSAL NERVE

Function of the Hypoglossal nerve is mainly motor in that it provides motor innervation to the muscles of tongue (except for the palatoglossus which is innervated by the Vagus nerve) and other glossal muscles. The Hypoglossal nerve is important for swallowing and speech formation.