Cranial Nerves

Wendy M. Rappazzo Harford Community College, July 2009

Cranial Nerves

• This tutorial will allow you to learn about the 12 pairs of cranial nerves in the human body.

• An introduction to the cranial nerves is followed by a screen which allows you to click on the nerve name to learn the functions and tests for the assessment for each nerve.

• At the end is a review exercise for you to write up.


Cranial NervesThere are 12 pairs of

cranial nerves.

They emerge from the inferior portion of the brain.


Cranial NervesCranial nerves can be purely sensory in function. Three cranial nerves are sensory nerves. These are the:

OlfactoryOptic &

Vestibulocochlear (auditory) nerves


Cranial Nerves

Cranial nerves can also be purely motor in function. Five cranial nerves are motor nerves. These are the:

OcculomotorTrochlearAbducensAccessory (spinal

accessory)Hypoglossal


Cranial NervesSome cranial nerves are

mixed nerves, like spinal nerves. Four cranial nerves are mixed nerves. These are the:TrigeminalFacialGlossopharyngealVagus


Cranial NervesClick on the cranial nerve

name from the list below to study it in more detail.

OlfactoryOpticOculomotorTrochlearTrigeminalAbducensFacialVestibulocochlearGlossopharyngealVagusAccessoryHypoglossal

Conclusion & Review Questions


Cranial Nerve I - OlfactoryThe Olfactory nerve is a

sensory nerve.

It functions to bring sensory information from the olfactory receptors in the nasal cavity to the brain. The olfactory nerves begin as bundles and pass through the cribriform plate to get to the brain.


Cranial Nerve I - Olfactory

This nerve is tested by assessing the ability to smell and identify different substances. Try this with coffee, vanilla, lemon, and cologne.

Back to Cranial Nerve Index


Cranial Nerve II - Optic NerveThe Optic nerve is a sensory

nerve.

It functions to bring sensory information from the retina to the brain. It passes through the optic canal of the sphenoid bone to get to the brain.


Cranial Nerve II – Optic Nerve

This nerve is tested by assessing a person’s vision.

Above image from: http://www.eyecaretyler.com/art/chart.gif


http://www.eyecaretyler.com/art/chart.gif


Cranial Nerve III - OculomotorThe Oculomotor nerve is a

motor nerve.

It functions to bring somatic motor information to the eye muscles & upper eyelid from the brain. It also controls the iris via autonomic motor axons. It passes through the superior orbital fissure to reach these muscles.

Above image from Marieb, Elaine Human Anatomy & Physiology, 8th ed. Pearson, Benjamin Cummings


Cranial Nerve III - OculomotorThis nerve is tested by

having a person follow an object with their eyes. The autonomic portion is easily tested via the pupil reflex. A penlight is used to shine light at the pupil, the pupil should constrict in response to bright light.

Above image from: http://leavingbio.net/THE%20SENSES_files/THE%20SENSES_files/image016.jpgBack to Cranial Nerve Index

http://leavingbio.net/THE%20SENSES_files/THE%20SENSES_files/image016.jpg


Cranial Nerve IV - TrochlearThe Trochlear nerve is a

motor nerve.

It functions to bring motor information from the brain to the superior oblique eye muscle. It passes through the superior orbital fissure to enter the orbit of the eye.



Cranial Nerve IV - TrochlearThis nerve is tested with the

occulomotor & abducens nerves by following an object with your eyes. If you hold a finger in front of the individual, move it up and down, then left and right and see if their eye can follow the movements.




Cranial Nerve V - TrigeminalThe Trigeminal nerve is a mixed

nerve. It carries both sensory and motor information.

It is a large nerve that consists of three branches:1.) Opthalmic2.) Maxillary3.) Mandibular

Each branch will be discussed individually.


Cranial Nerve V - TrigeminalThe Opthalmic branch is

sensory. It functions to carry sensory information (touch) from the cornea, orbit, upper eyelid, eyebrow, and part of the nose to the brain. It passes through the superior orbital fissure to reach the brain.


Cranial Nerve V - TrigeminalThe Maxillary branch is

sensory. It functions to carry sensory information (touch) from the lower eyelid, upper lip, gums, teeth, cheek, & nose to the brain. It passes through the foramen rotundum of the sphenoid bone to reach the brain.


Cranial Nerve V - TrigeminalThe Mandibular branch is

both sensory & motor. It functions to carry sensory information (touch) from the lower lip, gums & teeth to the brain. Its motor function is to the muscles of mastication. It passes through the foramen ovale of the sphenoid bone to reach the brain.


Cranial Nerve V - TrigeminalThis nerve is tested by touching

the areas of the face & gums associated with each branch. The corneal reflex is also used to test this nerve. Touching the cornea with cotton should cause blinking to occur.

Motor function of this nerve is assessed by having the individual clench his/her teeth.

Ophthalmic

MaxillaryMandibular



Cranial Nerve VI - AbducensThe Abducens nerve is a

motor nerve.

It functions to bring motor information from the brain to the lateral rectus eye muscle. It passes through the superior orbital fissure to the eye. It is named the abducens nerve because it abducts the eyeball.



Cranial Nerve VI - AbducensThis nerve is tested with the

occulomotor & trochlear nerves by following an object with your eyes. If you hold a finger in front of the individual, move it up and down, then left and right and see if the eye can follow the movements.




Cranial Nerve VII - FacialThe Facial nerve is a mixed

nerve. It carries sensory and both somatic & autonomic (parasympathetic) motor information.

It is a large nerve that consists of five branches:1.) Temporal2.) Zygomatic3.) Buccal4.) Mandibular4.) Cervical


Cranial Nerve VII - FacialSensory functions of the

facial nerve include taste (from the anterior 2/3 of the tongue) and sense of touch from the various regions of the face.


Cranial Nerve VII - FacialSomatic motor functions of

the facial nerve are shown by the ability to move the muscles of the face to smile, frown, and whistle.

The autonomic motor functions carried by this nerve innervate the lacrimal glands to cause tears.



Cranial Nerve VII - FacialBell’s Palsy is a disorder that

results in an inflammation of the facial nerve. This condition often causes paralysis of the affected side (facial drooping) and a loss of taste from the anterior region of the tongue.

The exact cause of this is not known but it is thought to result from a viral infection, such as herpes simplex.

Above image from http://www.aafp.org/afp/AFPprinter/20071001/afp20071001p1004-uf1.gifBack to Cranial

Nerve Index

http://www.aafp.org/afp/AFPprinter/20071001/afp20071001p1004-uf1.gif

http://www.aafp.org/afp/AFPprinter/20071001/afp20071001p1004-uf1.gif


Cranial Nerve VIII – VestibulocochlearThe vestibulocochlear nerve is

a sensory nerve. It is also known as the auditory or acoustic nerve.

It functions to bring sensory information from the hearing and equilibrium receptors in the inner ear to the brain. It has 2 main branches:1.) cochlear (hearing)2.) vestibular (equilibrium)


Cranial Nerve VIII – VestibulocochlearThe vestibulocochlear nerve

passes through the internal acoustic canal (meatus) to enter the brain.

This nerve is tested by conducting hearing tests. In a quiet room see if you can hear the ticking of a watch and identify where it is.



Cranial Nerve IX – GlossopharyngealThe glossopharyngeal is a

mixed nerve that passes through the jugular foramen to the brain.

This nerve transports sensory information from taste receptors on the posterior 1/3 of the tongue & pharynx. It also relays chemoreceptor information from the carotid sinus in the carotid artery to control blood pressure.


Cranial Nerve IX – Glossopharyngeal

The glossopharyngeal nerve also carries somatic information to muscles of the pharynx for swallowing and autonomic (parasympathetic) motor information to the salivary glands.



Cranial Nerve X – VagusThe vagus nerve is a mixed

nerve. It transports sensory and autonomic (parasympathetic) motor information

It passes through the jugular foramen to enter/exit the brain.

Above image from Marieb, Elaine Human Anatomy & Physiology, 8 th ed. Pearson, Benjamin Cummings


Cranial Nerve X – VagusIts sensory function is to

transport information for taste from the pharynx and sensory information from the visceral organs of the thoracic and abdominopelvic cavities. It also brings baroreceptor & chemoreceptor information from the aortic body in the aortic arch to the medulla oblongata to control HR & BP.



Cranial Nerve X – VagusThe vagus nerve is a critical

nerve for supplying parasympathetic information to the visceral organs of the respiratory, digestive and urinary systems. It is important in the control of heart rate, bronchoconstriction & digestive processes.


Cranial Nerve X – VagusTesting for the proper

functioning of the vagus nerve is accomplished by seeing if the individual has any difficulty swallowing. Also measuring HR can provide additional information about the function of this nerve.



Cranial Nerve XI – AccessoryThe Accessory (Spinal Accessory)

nerves are motor nerves. They have roots that begin on the cervical segments of the spinal cord. The roots travel up through the foramen magnum and join cranial fibers to form the accessory nerve which then pass through the jugular foramen to carry somatic motor information to skeletal muscles of the neck and upper back.


Cranial Nerve XI – AccessoryTesting the function of the

accessory nerve is simple. Since it innervates the trapezius and sternocleidomastoid muscles, you can check this by having the individual shrug their shoulders and turn their head/neck.




Cranial Nerve XII – HypoglossalThe Hypoglossal nerve is a

motor nerve that innervates the tongue.

It passes through the hypoglossal canal of the occipital bone to travel to the muscles of the tongue.


Cranial Nerve XII – HypoglossalThis nerve is tested by having

the individual stick their tongue out and move it.



Cranial NervesIn conclusion, the cranial

nerves consist of 12 pairs of nerves that have critical functions for sensory, somatic and autonomic motor control over the body.

The next slide contains a cranial nerve review to test your knowledge of the cranial nerves


Martini, F.H., & Nath , J.L. (2009). Fundamentals of Anatomy & Physiology. 8th ed. New York: Pearson, Benjamin Cummings.

Marieb, E.N., & Hoehn, K. (2010). Human Anatomy & Physiology. 8th edition. New York: Pearson, Benjamin Cummings.

Marieb. (2008). Human Anatomy & Physiology Laboratory Manual, Main Version. 8th edition. New York: Pearson, Benjamin Cummings.

Cranial Nerves

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