Cranial Nerves

April 21, 2021 with Test Your Knowledge at the end

Cranial nerves are pairs of nerves that connect the brain to different parts of the head, neck, and trunk. There are 12 cranial nerves in total, each named for their function or structure.

Each nerve has a corresponding Roman numeral between I (one) and XII (twelve). The numeral is based on their location from front to back. The olfactory nerve is designated as I, as it is closest to the front of the head.

Here are the 12 cranial nerves:

I.  Olfactory nerve

II. Optic nerve

III. Oculomotor nerve

IV. Trochlear nerve

V. Trigeminal nerve

VI. Abducens nerve

VII. Facial nerve

VIII. Vestibulocochlear nerve

IX. Glossopharyngeal nerve

X. Vagus nerve

XI. Accessory nerve

XII. Hypoglossal nerve

How about a mnemonic to help you remember them? There are many — this is one of the cleaner ones!

On ole Olympus towering top, a Finn and German viewed a hop.

  • Each word in the mnemonic starts with a letter that is the same as the cranial nerve.

  • So, on is for olfactory – ole is for optic – Olympus is for oculomotor – towering is for trochlear - top is for trigeminal - a is for abducens - etc.

  • One slight exception is that the a in “and” is for acoustic which is hearing which is Vestibulocochlear.

Briefly, this is what each cranial nerve is involved in. If you see *, that means the nerve has something to do with sucking and swallowing.

  • I. Olfactory nerve: sense of smell

  • II. Optic: sight

  • III. Oculomotor nerve: eye movement

  • IV. Trochlear nerve: eye movement

  • V. Trigeminal*: tri means three / this nerve has three branches / sensory of the face and motor, specifically muscles involved in chewing

  • VI. Abducens nerve: eye movement

  • VII. Facial*: motor nerve of facial muscles (facial expression) / sensation of taste for front 2/3 of tongue

  • VIII. Vestibulocochlear nerve: hearing and balance (equilibrium)

  • IX. Glossopharyngeal nerve*: pharynx, swallowing, sensation of taste for back 1/3 of tongue

  • X. Vagus nerve*: larynx and pharynx/ this nerve has the longest pathway/ parasympathetic function / cardiac, pulmonary, digestive, urinary

  • XI. Accessory nerve*: muscles that move the neck and shoulder

  • XII. Hypoglossal nerve*: responsible for the movement of most of the muscles of the tongue / tongue movements for speech, food manipulation and swallowing

Cranial nerves can be involed with just motor functions, just sensory functions or both. Motor nerves control the movement and function of muscles and glands. Sensory nerves are involved with the senses, such as smell, hearing, or touch. As mentioned, some cranial nerves have both functions.

Here is a mnemonic to remember functions of the cranial nerves. Again, trying to keep this rated PG but I figure this is a group comfortable with breasts so here goes. The key is S=Sensory, M=Motor, B=Both.

Some Say Marry Money, But My Brother Says Big Boobs Matter Most

  • Some starts with S so the first cranial nerve has a sensory function - olfactory - smell

  • Say starts with S so the second cranial nerve has a sensory function - optic - sight

  • Marry starts with M so the third cranial nerve has a motor function - oculomotor - eye movement

  • Again, I am not sure who to give credit to - found it on the internet.

Five Questions to Test Your Knowledge

1. Damage to this nerve may cause failure of the gag reflex.

A) VII. Facial nerve

B) XI. Accessory nerve

C) V. Trigeminal nerve

D) IX. Glossopharyngeal nerve

2. Which cranial nerve is most responsible for the movement of the tongue?

A) XI. Accessory nerve

B) X. Vagus nerve

C) XII. Hypoglossal nerve

D) V. Trigeminal nerve

3. A one-day old newborn has a facial droop noticed on the left side. Which cranial nerve may be affected?

A) I. Olfactory nerve

B) II. Optic

C) VII. Facial nerve

D) XII. Hypoglossal nerve

4. A problem with this cranial nerve can cause Bell’s Palsy.

A) VII. Facial nerve

B) VIII. Vestibulocochlear nerve

C) X. Vagus nerve

D) XI. Accessory nerve

5. A mother of a one-month old says she (the mother) can’t taste anything on the front of her tongue. This could be due to a problem with this cranial nerve.

A) IV. Trochlear

B) VI. Abducens

C) VII. Facial

D) IX. Glossopharyngeal

6. What cranial nerve is involved in chewing (mastication)?

A) V. Trigeminal nerve

B) VI. Abducens nerve

C) XI. Accessory nerve

D) IV. Trochlear nerve

Answers

1. The answer is D) IX. Glossopharyngeal nerve. This cranial nerve controls the gag response in the soft palate and posterior tongue. The X. Vagus nerve is also involved but that is not a choice. Gag - 9 and 10. (To help me get half way there with the answer I remember Gag - G, glossopharyngeal - 9.)

2. The answer is C) XII. Hypoglossal nerve. Remember that the hypoglossal cranial nerve is the primary motor nerve of the tongue. If you had no idea you could probably guess this answer if you remembered that glossal means “of the tongue.” Tongue movements - 12.

3. The answer is C) VII. Facial nerve. Using good test taking skills you could get this. Olfactory is associated with a sensation, smell, so that’s out. Optic is associated with a sensation, sight, so that’s out. Hypoglossal is associated with motor but motor of the tongue, so that’s out. The motor function of the facial nerve is for facial expressions - bingo!

4. The answer is A) VII. Facial nerve. It helps to know that a common cause of facial palsy is Bell’s Palsy. Facial expressions - 7.

5. The answer is C) VII. Facial nerve. Of the 12 cranial nerves, 7 and 9 have to do with tongue taste: VII. Facial nerve supplies sensation of taste for front 2/3 of the tongue; IX. Glossopharyngeal nerve provides the sensation of taste for the back 1/3. Taste 7 and 9.

6. The answer is A) V. Trigeminal nerve. Remember chewing is Cranial Nerve V. Chewing-5.

Repeat after me (over and over and over again):

On ole Olympus towering top, a Finn and German viewed a hop.

Some Say Marry Money, But My Brother Says Big Boobs Matter Most

Share

Share The Lactation College