Cranial Nerves

Question 1

What is the Order of Cranial Nerves?

Answer 1

1. Olfactory nerve (CN I),
2. Optic nerve (CN II),
3. Oculomotor nerve (CN III),
4. Trochlear nerve (CN IV),
5. Trigeminal nerve (CN V),
6. Abducens nerve (CN VI),
7. Facial nerve (CN VII),
8. Vestibulocochlear nerve (CN VIII),
9. Glossopharyngeal nerve (CN IX),
10. Vagus nerve (CN X),
11. Accessory nerve (CN XI),
12. Hypoglossal nerve (CN XII).

On, On, On, They Traveled And Found Voldemort Guarding Very Ancient Horcruxes.

Question 2

CN I.
What is it Called?
Found Where?
Where is the synapse?
2 specialities - other CN DO NOT HAVE.
(6)

What does it do?
What does it contain?

Answer 2

1. Olfactory Nerve: Sense of smell.
2. Special Sensory Fibres
3. Superior nasal Cavity —> Cribriform plate.
4. Synapse in Olfactory Bulb
5. Only cranial nerve to BYPASS THALAMUS
6. Only the cranial nerve to Regenerate.

Question 3

CN II.
What is it Called?
What does it do? what does it contain?
Found Where?
Where is the synapse?
Other specifics
(6)

Answer 3

1. Optic Nerve - Ability to see.
2. Special Sensory Fibers
3. Vision (3-neuron pathway)
4. Orbital cavity —> Optic canal
5. Ganglion Cells
6. Primary visual cortex (Striate cortex of occipital lobe)

Question 4

CN III.
What is it Called?
What does it do?
Found Where?
Other specifics GSE, GVE
What does it contain?
(6)

Answer 4

1. Oculomotor Nerve - Ability to move and blink your eyes. Several movements assist with this process: saccades, smooth pursuit, fixation, accommodation, vestibulo-ocular reflex, and optokinetic reflex.
2. General somatic efferent (motor fibers)
3. General Visceral efferent (Parasympathetic fibres)
4. Exits cranium vis superior orbital fissure
5. GSE: superoir rectus m., inferior rectus m., medial rectus m., inferior oblique m., levator palpebrae superioris m.
   (GSE fibers carry motor signals to skeletal muscles derived from embryonic somites.)

6.GVE: sphincter Pupillae
(GVE fibers provide motor (parasympathetic) innervation to the viscera).

Question 5

CN IV.
What is it Called?
What does it do?
Found Where?
Other specifics GSE, GVE
What does it contain?
(5)

Answer 5

1. Trochlear Nerve - Ability to move your eyes up and down or back and forth.
2. Contains General somatic fibres
3. Only Cranial Nerve to EMERGE from Posterior Brainstem
4. Exits Cranium via a superior orbital fissure
5. Supplies superior Olibque m.

Question 6

CN V:
CN IV.
What is it Called?
What does it do?
Found Where?
Other specifics - DIVISIONS
What does it contain?
(5)

Answer 6

1. Trigeminal Nerve - Sensations in your face and cheeks, taste and jaw movements.
2. 3 Divisions
   —–1. CN V1 = ophthalmic n. exits via a superior orbital fissure
   ——2. CN V2: maxillary nerve exits via foramen rotundum
   ——3. CN V3: Mandibular n. exits via foramen ovale.
3. CNV1 AND CNV2 = SENSORY ONLY. GSA fibres
4. CN V3 = GSA + special visceral Efferent fibres.
5. SVE fibres to 1st pharyngeal arch derivatives (mastication mm+ tensor tympani m., tensor veli palatine m., anterior belly of digastric m., mylohyoid m.)

Question 7

What are the 3 divisions of CN V

Answer 7

3 Divisions
—–1. CN V1 = ophthalmic n. exits via superior orbital fissure
——2. CN V2: maxillary nerve exits via foramen rotundum
——3. CN V3: Mandibular n. exits via foramen ovale.

The trigeminal nerves play essential roles in helping your face feel pain, touch, warmth or cold.

The peripheral aspect of the trigeminal ganglion gives rise to 3 divisions: ophthalmic (V1), maxillary (V2) and mandibular (V3).

Question 8

CN VI: What is it Called?
What does it do?
Found Where?
Other specifics - DIVISIONS
What does it contain?
(4)

Answer 8

1. Abducens nerve - Ability to move your eyes
2. General somatic efferent fibres
3. Exits cranium via a superior orbital fissure
4. Supplies lateral rectus m. The abducens nerve controls the movement of a single muscle, the lateral rectus muscle of the eye - moves the eye laterally, and side to side

Question 9

CN VII
What is it Called?
What does it do?
Found Where?
Other specifics -post and pre ganglionic travel, branches?
What does it contain?
(4)

Answer 9

1. Facial Nerve - Facial expressions and sense of taste.a
2. 2nd pharyngeal arch
3. Facial nerve proper (motor) + nervous intermedius (parasympathetic + taste fibres)
4. Enter temporal bone through internal acoustic meatus.
5. Before exiting the temporal bone, the facial nerve supplies stapedius m.
6. Major motor branch of the FACIAL NERVE exits the cranium via the STYLOMASTOID FORAMEN.
7. 6 Terminal Motor branches supply the facial nerve expression
8. Special sensory fibres (Taste) travel via CHORDA TYMPANI and HITCH-HIKE with LINGUAL n. to serve the anterior 2/3rds of the TONGUE.
9. Pre-ganglionic parasympathetic fibres travel in the greater petrosal n. to synapse in the pterygopalatine ganglion.
10. Postganglionic parasympathetic fibres hitch-hike with CN V BRANCHES TO LACRIMAL AND NASAL GLANDS.
11. Pre-ganglionic parasympathetic fibres travel in the CHORDA RYMPANI to SYNAPSE in the SUBMANDIBULAR GANGLION.
12. Post Ganglionic parasympathetic fibres hitch-hike with CNV branches to SUBLINGUAL and SUBMANDIBULAR SALIVARY GLANDS.

Question 10

CNVIII

What is it Called?
What does it do?
Found Where?
Other specifics
What does it contain?

(4)

Answer 10

1. Vestibulocochlear nerve. - Auditory/vestibular nerve: Sense of hearing and balance.
2. Special sensory fibres (Balance and Hearing)
3. Vestibular nerve receives balance information from the vestibular apparatus.
4. Cochlea nerve receives auditory information from the spiral ganglion in the cochlea.

Question 11

CN IX What is it Called?
What does it do?
Found Where?
Other specifics -post and preganglionic travel, sensory?
What does it contain?

(6)

Answer 11

1. Glossopharyngeal nerve. - Ability to taste and swallow.
2. 3RD pharyngeal arch
3. Exits cranium via the jugular foramen
4. Motor: stylopharyngeus m.
5. Sensory: Carotid sinus (chemoreceptors +baroreceptors)
   Posterior 1/3 tongue (general + taste).
   tympanic cavity,
   pharyngotympanic tube,
   nasopharynx, tonsils.
6. Preganglionic parasympathetic fibres travel in the lesser petrosal nerve. to synapse in the otic ganglion. Postganglionic parasympathetic fibres hitch-hike with CN 3 branches to the parotid salivary gland.

Question 12

CN X What is it Called?
What does it do?
Found Where?
Other specifics - sensory?
What does it contain?

SUPPLY? BRANCHES - WHERE?

(11)

Answer 12

1. Vagus nerve - Digestion and heart rate.
2. 4th + 6th pharyngeal arch
3. exits cranium via the jugular foramen
4. Travels in the carotid sheath with IJv +CCa
5. Motor innervation majority of the soft palate, pharyngeal and laryngeal muscles
6. Sensory to the skin of external acoustic meatus and internal surfaces of larynx and pharynx.
7. Special sensory fibres (taste) from the epiglottis and root of the tongue.
8. Parasympathetic supply to structures in the thorax and abdomen along to the splenic flexure.
9. Internal branch of superior laryngeal n. supplies sensory innervation to the larynx above the vocal cords.
10. External branch of superior laryngeal n. supplies cricothyroid m.
11. Recurrent laryngeal nerve ascends in the tracheoesophageal groove to innervate all the other intrinsic laryngeal muscles.

Question 13

CN XI
What is it Called?
What does it do?
Found Where?
Other specifics -MUSCLES?
What does it contain?

(4)

Answer 13

1. Spinal Accessory - Shoulder and neck muscle movement
2. Originates in the Superior cervical spinal cord
3. enters cranium via the jugular foramen and then promptly exits again via the jugular foramen.
4. Supplies motor fibres to 2 large muscles:
   - STERNOCLEIDOMASTIOD and TRAPEZIUS

Question 14

CN XII
What is it Called?
What does it do?
Found Where?
Other specifics -MUSCLES?
What does it contain?

(4)

Answer 14

1. Hypoglossal Nerve - Ability to move your tongue.
2. Emerges from medulla oblongata between pyramids and olives.
3. Exits cranium through the hypoglossal canal
4. Innervates the majority of the tongue muscles, except palatoglossus.

Question 15

Explain Ophthalmic Nerve

Answer 15

Ophthalmic nerve gives rise to 3 terminal branches: frontal, lacrimal and nasociliary, which innervate the skin and mucous membrane of derivatives of the frontonasal prominence derivatives:

Forehead and scalp
Frontal and ethmoidal sinus
Upper eyelid and its conjunctiva
Cornea (see clinical relevance)
Dorsum of the nose
Parasympathetic Supply:

Lacrimal gland: Post ganglionic fibres from the pterygopalatine ganglion (derived from the facial nerve), travel with the zygomatic branch of V2 and then join the lacrimal branch of V1. The fibres supply parasympathetic innervation to the lacrimal gland.

Question 16

Explain Maxillary Nerve

Answer 16

Maxillary Nerve
Maxillary nerve gives rise to 14 terminal branches, which innervate the skin, mucous membranes and sinuses of derivatives of the maxillary prominence of the 1st pharyngeal arch:

Lower eyelid and its conjunctiva
Cheeks and maxillary sinus
Nasal cavity and lateral nose
Upper lip
Upper molar, incisor and canine teeth and the associated gingiva
Superior palate
Parasympathetic Supply:

Lacrimal gland: Post ganglionic fibres from the pterygopalatine ganglion (derived from the facial nerve), travel with the zygomatic branch of V2 and then join the lacrimal branch of V1. The fibres supply parasympathetic innervation to the lacrimal gland.
Nasal glands: Parasympathetic fibres are also carried to the mucous glands of the nasal mucosa. Post-ganglionic fibres travel with the nasopalatine and greater palatine nerves (branches of V2)

Question 17

Explain Mandibular Nerve

Answer 17

Mandibular Nerve

Mandibular nerve gives rise to four terminal branches in the infra-temporal fossa: buccal nerve, inferior alveolar nerve, auriculotemporal nerve and lingual nerve.

These branches innervate the skin, mucous membrane and striated muscle derivatives of the mandibular prominence of the 1st pharyngeal arch.

Sensory supply:

Mucous membranes and floor of the oral cavity
External ear
Lower lip
Chin
Anterior 2/3 of the tongue (only general sensation; special taste sensation supplied by the chorda tympani, a branch of the facial nerve)
Lower molar, incisor and canine teeth and the associated gingiva
Motor Supply:

Muscles of mastication; medial pterygoid, lateral pterygoid, masseter, temporalis
Anterior belly of the digastric muscle and the mylohyoid muscle (these are suprahyoid muscles)
Tensor veli palatini
Tensor tympani
Parasympathetic Supply:

Submandibular and Sublingual glands: Post-ganglionic fibres from the submandibular ganglion (derived from the facial nerve), travel with the lingual nerve to innervate these glands.
Parotid gland: Post-ganglionic fibres from the otic ganglion (derived from the glossopharyngeal nerve, CN IX), travel with the auriculotemporal branch of the V3 to innervate the parotid gland.