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Category: Medical

Topic: Nervous System A&P

Level: Paramedic

Next Unit: Sensory and Motor Pathways

10 minute read


The peripheral nervous system includes the 12 cranial nerves:

  1. olfactory nerve (I),
  2. the optic nerves (II),
  3. the oculomotor nerves (III),
  4. the trochlear nerves (IV),
  5. the trigeminal nerves (V),
  6. the abducens nerves (VI),
  7. the facial nerves (VII),
  8. the vestibulocochlear nerves (VIII),
  9. the glossopharyngeal nerves (IX),
  10. the vagus nerves (X),
  11. the accessory nerves (XI), and
  12. the hypoglossal nerves (XII).


Cranial Nerve Functions

CN I: The OLFACTORY NERVE is cranial nerve 1, and is the nerve that facilitates the sense of smell.

The nerves involved in taste are the olfactory (I), Facial (VII), and Glossopharyngeal (IX).

Mnemonic: "1-7-9 is one heavenly wine."

CN II: The OPTIC NERVE is a paired nerve (one for each eye) known as cranial nerve 2 that transmits information to the brain from the retina at the back of the eye and facilitates sight.

CN III: The OCULOMOTOR NERVE is cranial nerve 3 and controls some movement of the eyes.

CN IV: The TROCHLEAR NERVE is cranial nerve 4 and has specific control over the superior oblique muscle that connects to the eye and allows for the ability to look up and down.

CN V: The TRIGEMINAL NERVE is cranial nerve 5 and is responsible for sensation in the face and motor functions such as biting and chewing. As the name implies, it has 3 parts:

  • ophthalmic nerve (purely sensory)
  • maxillary nerve (purely sensory)
  • mandibular nerve (motor and sensory functions)

CN VI: The ABDUCENS NERVE is cranial nerve 6 and allows for movement of the eye outward.

Thus, the eyes have 3 of the cranial nerves all to themselves to control the eye-movement muscles: CNs III, IV, and VI.

CN VII: The FACIAL NERVE is cranial nerve 7 and controls facial expression and the sense of taste.

The nerves involved in taste are the Olfactory (I), Facial (VII), and Glossopharyngeal (IX).

CN VIII: The VESTIBULOCOCHLEAR NERVE  is cranial nerve 8 and is responsible for transmitting sound (via its cochlear nerve branch) and equilibrium information from the inner ear (via its vestibular nerve branch) to the brain.

CN IX: The GLOSSOPHARYNGEAL NERVE  is known as cranial nerve 9 and is responsible (along with the facial nerve) for the sense of taste, as well as the function of swallowing. It provides the sensory stimulation for the gag reflex (CN X provides the motor portion of the gag reflex). 

The nerves involved in taste are the olfactory (I), Facial (VII), and Glossopharyngeal (IX).

CN X: The VAGUS NERVE is known as cranial nerve 10 and is responsible for the sensory, motor, and autonomic functions of the organs, including glands, digestion, and heart rate.

The Vagus Nerve, the longest nerve in the autonomic nervous system, is so named because it was originally described as "wandering." That is, it has so many functions in so many organs that it is difficult to describe its function succinctly. Besides innovating parasympathetic pathways to modulate heart rate and breathing, it is also a major stimulant for gastric acid production and other GI functions. 

CN XI: The ACCESSORY NERVE is known as cranial nerve 11 and controls the sternocleidomastoid muscle and the trapezius muscles that allow movement of the head.

CN XII: The HYPOGLOSSAL NERVE is known as cranial nerve 12 and controls the muscles of the tongue and allows for tongue movement.



Oh, Oh, Oh To Touch And Feel Very Good Velvet, Ah Heaven!

On Old Olympus' Towering Tops, A Finn Viewed Grapes, Vines, And Hops.

Onions Only Offer Tasty Toppings After Frying Vegetables Gently, Vinegar Adds Harmony

Only Optimistic Orcas Traverse Tributaries Adapting Finely, Viewing Glacier Vistas, Avoiding Humans.

Once On October Thirteenth, Troubadours Ate Fifty Vegetable Green Vegetable Soups And Hamburgers.


The mnemonic for CN control for eye muscles (EXTRAOCULAR MUSCLES) is:

"LR6 - SO4 - R3," that is, 

  • LR6 (Lateral Rectus via CN VI, the abducens); 
  • SO4 (Superior Oblique via CN IV, the trochlear); and 
  • R3 (all of the Remaining eyeball movers via CN III, the oculomotor)