Lecture 17: Cranial Nerves
M/O Chapter 15
81. List the cranial nerves by name and number.
82. Describe the specific functions of each of the cranial nerves and classify each as sensory, motor, or
mixed.
What are Cranial Nerves?
Cranial nerves are nerves that arise from the inferior surface of the brain. They are part of the PNS and are numbered 1-12 (in Roman
numerals, of course.) Today we will learn the FUNCTIONS of all 12 cranial nerves. In lab, we will see how they get from the brain
into the periphery.
1. Cranial nerves are numbered by how they exit the brain, from anterior to posterior. Therefore, CN I is the most anterior cranial
nerve and CN X11 is the most posterior.
2. Each cranial nerve has a name that is usually related to its function....usually. You will need to know both name and number.
3. Each cranial nerve carries out specific functions. A failure to perform a function can be used to diagnose damage to the specific
cranial nerve.
4. Cranial nerves contain different types of fibers, depending on the nerve. Therefore, each cranial nerve can be classified by what
kinds of fibers it contains.
The Massive Data Chart
#
I
Cranial Nerve
Fiber Type
SM Function
VM Function
Sensory Function
Cranial Exit
Damage...?
II
III
IV
V
V1
V2
V3
VI
VII
VIII
IX
X
XI
XII
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PERIPHERAL NERVE WORKSHEET
Name the peripheral nerve/s implicated in each of the following situations. Be specific!
The same nerve might be used more than once.
1. A patient complains of right arm weakness. You ask them to hold a book in the palm of their hand and lift it by flexing at the
elbow. They can’t.
2. A patient comes to you drooling excessively.
3. You ask a patient to turn their head to one side, looking over their shoulder. They can’t.
4. A patient fails to exhibit a papillary reflex in response to a penlight in the eye.
5. Your 10 year old sister has her belly button pierced. She says she didn’t feel a thing.
6. You ask a patient to stand with their arms outstretched to the side but they can’t abduct their left arm.
7. A patient exhibits hypercontracted forearm flexors. Clearly the median nerve is working, too well. You suspect that the nerve
supplying antagonist muscles is damaged.
8. You ask a patient to shrug their shoulders. They can’t.
9. Once again, you forgot to put sunscreen on the back of your neck, and you spent the whole day at the beach. Ouch!
10. You see somebody walking, and they’re dragging their toes on the ground when they swing their leg forwards.
11. Too many late nights studying, partying, studying, partying…now your throat hurts so much you can’t swallow, and you suspect
you have strep throat (give both the nerve for the pain and the swallowing).
12. Your daughter wakes up in the middle of the night with a raging fever, screaming, and tugging on her ear. You suspect a middle
ear infection.
13. Anatomy tests make you tense and you’ve been clenching your jaws.
14. Now you have a headache. Your headaches are always above your eyebrow.
15. Racing to class, you bang your elbow on a door jamb and now you have alternating shooting pains and tingling numbness in the
part of your palm proximal to your pinky.
16. A patient came in complaining of vision problems…MRI scan shows a pituitary tumor.
17. The doctor says stick out your tongue and say ahhhhh…you gag.
18. Patient comes in with obviously atrophied quadriceps muscles in the left leg.
19. You see someone walking with the “Trendelenburg lurch”, and suspect their gluteus group is compromised.
20. A patient has trouble tapping their toes, and their foot seems excessively everted.
21. After your son’s humeral compound fracture has set during two months in a cast, and after physical therapy to restore muscle
tone, he still can’t extend his arm fully. You suspect previously undetected nerve damage.
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Lab 17: Cranial Nerves
Reading: M&O Ch. 15
I. Cranial Nerves
Identify the following nerves on both sheep brains and the human brains. If you can’t seem to find some of them, ask! Many times
they have been removed by rough handling. Note that the nerves are numbered in sequence from anterior to posterior.
As you find each nerve, ask yourself what kinds of information it carries to/ from what region of the head or body. This information is
as important as being able to identify the nerves!!!!! M&O Table 15.7 is an essential reference for this material.
#
Cranial nerve
Function(s)
Fiber types How does it get out of the brain? (Be able
to identify these holes and the CN that runs
through them!)
I
II
III
IV
V
V1
V2
V3
VI
VII
VIII
IX
X
XI
XII
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External Brain 17: Cranial Nerves
81. List the cranial nerves by name and number.
82. Describe the specific functions of each of the cranial nerves and classify each as sensory, motor, or
mixed.
Study Questions
1. Make a visual of the cranial nerves that clearly illustrates the types of fibers that run through each nerve. Fill in the chart with
specific examples. Your chart might look something like this:
#
CN Name
Somatic Motor/Action Visceral Motor/Action Somatic Sensory/Action
Visceral Sensory/Action
2. Come up with a way to test the function of each cranial nerve. Explain why your tests work.
3. Which nerves carry autonomic fibers?
4. Are any cranial nerves somatic sensory only?
5. Are any somatic motor only?
6. Which nerve carries the bulk of parasympathetic innervation to the body?
7. Which nerve innervates the trapezius?
8. How many nerves innervate the eye muscles?
9. Which nerve/s does your dentist try to anesthetize?
Bio 6: Human Anatomy
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Fall 2013: Riggs