CranialNerves

The cranial nerves are 12 pairs of nerves that can be seen on the ventral(bottom) surface of the brain. Some of these nerves bringinformation from the sense organs to the brain; other cranial nerves control muscles; other cranial nerves are connected to glands or internal organs (for example, the heart and lung). Here is atable detailing some of the functions of each cranialnerve.

Number	Name	Function
CranialNerves
I	Olfactory Nerve	Smell
II	Optic Nerve	Vision
III	Oculomotor Nerve	Eye movement; Pupil dilation
IV	Trochlear Nerve	Eye movement
V	Trigeminal Nerve	Somatosensory information (touch, pain) from the face and head; muscles for chewing.
VI	Abducens Nerve	Eye Movement
VII	Facial Nerve	Taste (anterior 2/3 of tongue);Somatosensory information from ear;Controls muscles used in facial expression.
VIII	Vestibulocochlear Nerve	Hearing; Balance
IX	Glossopharyngeal Nerve	Taste (posterior 1/3 of tongue);Somatosensory information from tongue, tonsil, pharynx; Controls somemuscles used in swallowing.
X	Vagus Nerve	Sensory, motor and autonomic functions ofviscera (glands, digestion, heart rate)
XI	Spinal Accessory Nerve	Controls muscles used in headmovement.
XII	Hypoglossal Nerve	Controls muscles of tongue

HearIT!	Olfactory	Optic	Oculomotor	Trochlear
	Trigeminal	Abducens	Facial	Vestibulocochlear
	Glossopharyngeal	Vagus	Spinal Accessory	Hypoglossal

The Cranial Nerves

A large diagram of the cranial nerves and base of the brain from theUniversity of Connecticut. Beware, this image is huge(437K)!

Can't remember the names of the cranial nerves? Here is a handy-dandy mnemonic for you:

On OldOlympus ToweringTop AFamous Vocal German Viewed Some Hops.

The bold letters stand for:

olfactory, optic, oculomotor, trochlear, trigeminal, abducens, facial,vestibulocochlear, glossopharyngeal, vagus, spinal accessory,hypoglossal.

Test Your Cranial Nerves

Now that you know the names and functions of the cranial nerves, let'stest them. These tests will help you understand how the cranial nerveswork. These tests are not meant to be a "clinical examination" of thecranial nerves.

You will need to get a partner to help...both of you can serve asthe experimenter (tester) and the subject. Record your observation ofwhat your partner does and says.

Olfactory Nerve

Gather some items with distinctive smells (for example, cloves, lemon,chocolate). Have your partner smell the items one at a time with eachnostril. Have your partner record what the item is and the strength ofthe odor. Now you be the one who smells the items...have your partner usedifferent smells for you.

Optic Nerve

Make an eye chart like the one onthe right. It doesn't have to be perfect. Have your partner try to readthe lines at various distances away from the chart.

Oculomotor, Trochlear and AbducensNerves

Remember, these 3 nerves control eye movement. Hold up a finger infront of your partner. Tell your partner to hold his or her headstill and to follow your finger, then move your finger up and down, rightand left. Do your partner's eyes follow your fingers?

TrigeminalNerve

The trigeminal nerve is both sensory and motor. To test the motorpart of the nerve, tell your partner to close his or her jaws as if he orshe was biting down on a piece of gum.

To test the sensory part of the trigeminal nerve, lightly touch variousparts of your partner's face with piece of cotton or a blunt object. Becareful not to touch your partner's eyes. While much of the mouth andteeth are innervated by the trigeminal nerve, don't put anything into yoursubject's mouth.

Facial Nerve

The motor part of the facial nerve can be tested by asking yourpartner to smile or frown or make funny faces. The sensory part of thefacial nerve is responsible for taste on the front part of the tongue.You could try a few drops of salty water on this part of the tongue andsee if your partner can taste it.

VestibulocochlearNerve

While the vestibulocochlear nerve is responsible for hearing andbalance, we will only test the hearing portion of the nerve here. Haveyour partner close his or her eyes and determine the distance at which heor she can hear the ticking of a clock or stopwatch.

Glossopharyngeal and VagusNerve

Have your partner drink some water and observe the swallowing reflex.Also the glossopharyngeal nerve is responsible for taste on the back partof the tongue. You could try a few drops of salty (or sugar) water on thispart of the tongue and see if your partner can taste it.

Spinal Accessory Nerve

To test the strength of the muscles used in head movement, put youhands on the sides of your partner's head. Tell your partner to move hisor her head from side to side. Apply only light pressure when the head ismoved.

HypoglossalNerve

Have your partner stick out his or her tongue and move it side toside.

Try it!