Summary of the Cranial Nerves

The olfactory nerves are associated with the function of smell. The smell molecules in the nasal cavity trigger nerve impulses that pass along this nerve to the olfactory bulb, then onto limbic areas.

The type of modality is sensory, of the special visceral sensory variety.

The optic nerves are associated with the function of vision. Visual information from the retinas of the eyes is conveyed to the brain by the optic nerves at the back of the eye.

Both optic nerves from the eyes meet to form something called an optic chiasm. At the optic chiasm, signals from both fields of vision are sent to opposite sides of the brain via two separate optic tracts.

These signals will then eventually reach the visual cortex at the back of the brain. The type of modality of the optic nerve is sensory, of the special somatic sensory variety.

The oculomotor nerve is also associated with vision. This nerve provides motor function to most of the muscles around the eyes to help them move and focus on objects.

This nerve also functions in pupillary response to help control the size of the pupils as it responds to light, dilating and constricting the pupils.

This nerve originates from the front of the midbrain, which is part of the brain stem, moving from this area until it reaches the area of the eye sockets. The modality of this cranial nerve is motor, of the general somatic and general visceral motor variety.

The trochlear nerve controls the superior oblique muscles, which are the muscles that are responsible for downward, outward, and inward eye movements.

This nerve travels from the back of the midbrain to the eye sockets, where it stimulates these superior oblique muscles. The trochlear nerve is motor in modality of the general somatic motor variety.

The trigeminal nerve is the largest of the cranial nerves and can be further divided into three divisions: ophthalmic, maxillary, and mandibular.

The ophthalmic division sends information from the scalp, forehead, and upper eyelids (the upper parts of the head) and is sensory in modality, of the general somatic sensory variety.

The maxillary division sends information from the middle of the head, such as cheeks, lower eyelids, upper lip, and nasal cavity. This is also sensory or the general somatic sensory variety.

The mandibular division sends both sensory and motor information of the general somatic sensory and special visceral motor modalities.

This division sends information from the lower parts of the head, such as the tongue, lower lip, chin, and jaw.

The abducens nerve is another nerve that controls a muscle of the eye, called the lateral rectus muscle. This muscle is responsible for outward eye movements such as looking to the side.

This nerve originates in the pons and travels to the eye socket to control this muscle. This nerve sends motor information about the general somatic motor modality.

Facial nerves have both sensory and motor functions, such as collecting information from the taste buds of the tongue, controlling muscle movements required for facial expressions, and supplying glands that produce saliva and secrete tears.

Facial nerves originate from the pons area of the brainstem, where it has both motor and sensory roots, before fusing together to form the facial nerve.

The sensations from part of the external ear are of the general somatic sensory modality, taste is part of the special visceral sensory modality, the muscles of facial expressions are part of the special visceral sensory modality, and the lacrimal and mucous glands of the eyes, mouth, and nose are of the general visceral motor modality.

The vestibulocochlear nerve is associated with the function of hearing and consists of two divisions: cochlear and vestibular.

The vestibular branch collects information regarding the inner ear and head orientation and balance. The cochlear branch is concerned with sound and hearing signals from the ear, detecting vibrations from a sound’s volume and pitch. This information is sensory to the special somatic sensory modality.

The glossopharyngeal nerve has both motor and sensory functions originating from a part of the brainstem called the medulla oblongata, extending into the neck and throat.

This nerve sends sensory information from the external ear and middle ear cavity (general somatic sensory modality), the back part of the tongue (special visceral sensory modality), and from the sinuses at the back of the throat (general visceral sensory modality).

This nerve also sends motor information from two salivary glands called parotid glands (general visceral motor modality), and movement from a muscle at the back of the throat called the stylopharyngeus (special visceral motor modality).

The vagus nerve has a variety of functions and is the longest and most branched of all the cranial nerves with sensory, motor, and autonomic fibers.

It receives sensory information from the ear canal as well as the larynx and pharynx, which are parts of the throat (general somatic sensory modality), information from the organs of the chest and trunk such as the heart and intestines (general visceral sensory modality), and a sense of taste from the root of the tongue (special visceral sensory modality).

It also receives motor information from the smooth muscles of parts of the throat (general visceral motor modality), as well as most of the muscles of the throat (special visceral motor modality).

The spinal accessory nerve has motor functions associated with the muscles and movements of the head, neck, and shoulders. This also stimulates the muscles of the larynx and pharynx, which are responsible for swallowing.

Movements of the head and shoulders are of the general somatic motor modality, whereas the internal movements are of the special visceral motor modality.

The hypoglossal nerve is responsible for most of the movements in the tongue. These originate in the medulla oblongata and move down into the jaw, reaching the tongue.

This nerve is of the general somatic motor modality.