I. Olfactory nerve

It transmits the olfactory impulses.

II. Optical

Sensitive

It transmits visual information to the brain.

III. Oculomotor

Motor

It innervates the muscles: levator upper eyelid, upper rectus, medial rectus, inferior rectus, and inferior oblique, which collectively perform the majority of eye movements; it also innervates the sphincter of the pupil.

IV. Trochlear o Pathetic

Motor

It innervates the superior oblique muscle, which depresses, rotates laterally (around the optic axis), and internally rotates the eyeball.

V. Trigeminal

Mixed

It perceives sensitive information from the face and innervates the chewing muscles (masseter and temporal).

VI. External ocula motor

Motor

It innervates the superior oblique muscle, which depresses, rotates laterally (around the optic axis), and internally rotates the eyeball.

VII. Facial

Mixed

It carries motor innervation to the muscles responsible for facial expression, the posterior belly of the digastric muscle and the stapedium, receives the taste impulses from the anterior two thirds of the tongue and provides secret-motor innervation to the salivary (except for the parotid) and the lacrimal gland.

VIII. Vestibule-cochlear o auditory

Sensitive

Perception of sounds, rotation and gravity (essential for balance and movement). The vestibular branch carries impulses to coordinate balance and the cochlear arm carries auditory impulses.

IX. Glossopharyngeal

Mixed

It receives taste impulses from the posterior third of the tongue, provides secret-motor innervation to the parotid gland and motor innervation to the stylopharyngeus muscle and the styloglossus muscle. It also relays some information to the brain from the palatine tonsils. This is directed to the opposite thalamus and some nuclei of the hypothalamus.

X. Vagus.

Mixed

Provides innervation to most laryngeal muscles and all pharyngeal muscles except stylopharyngeal (innervated by glossopharyngeus); carries parasympathetic fibers to the vicinity of all abdominal viscera located below the splenic flexure; and receives the sense of taste from the epiglottis. It controls the muscles that help articulate sounds in the soft palate. Symptoms of damage generate dysphagia, velopharyngeal insufficiency.

XI. Accessory or spinal

Motor

It controls the sternocleidomastoid muscles and the trapezius, overlaps with functions of the vagus. Symptoms of damage include an inability to shrug the shoulders and a weakness in head movements.

XII. Hypoglossal nerve

Motor

It provides motor innervation to the muscles of the tongue (except the palatoglossus muscle, which is innervated by the vagus nerve, and the styloglossus muscle, which is innervated by the glossopharyngeal nerve) and other lingual muscles. Important in swallowing (bolus formation) and articulation of sounds.