Lab 10

Question 1

Cranial Nerves overview

Answer 1

• PNS
• sensory and motor nerve fibers that innervate head/neck/viscera
• originate from brain or brainstem and exit through foramen in skull
• named in order from anterior to posterior
• 12 pairs: 3 sensory, 5 motor, 4 mixed

Question 2

CN Mnemonic

Answer 2

• On Occasion Our Trusty Truck Acts Funny Very Good Vehicle Any How
• Olfactory, Optic, Oculomotor, Trochlear, Trigeminal, Abducens, Facial, Vestibulocochlear, Glossopharyngeal, Vagus, (Spinal) Accessory, Hypoglossal

Question 3

Olfactory CN I

Answer 3

Sensory: olfaction (smell)
- origin: olfactory epithelium (end in posterior olfactory cortex)
- enters cranial cavity via foramina in cribriform plate
- olfactory bulb and tract

Question 4

Optic CNII

Answer 4

• technically a brain tract, half nerve fibers cross at optic chiasm
• sensory: vision
• origin: retina of the eye (end in primary visual cortex)
• enters cranial cavity via the optic canal

Question 5

Vestibulocochlear CN VIII

Answer 5

• sensory: hearing and balance (equilibrium)
• origin: inner ear, connect to brain stem at pons
• fibers from cochlea and semicircular canals enter cranial cavity via internal auditory meatus

Question 6

Oculomotor CN III

Answer 6

• eye-mover
• motor: superior/inferior/medial rectus, inferior oblique
• exit cranial cavity via superior orbital fissure to enter to orbit

Question 7

Trochlear CN IV

Answer 7

• motor: superior oblique
• origin: midbrain
• exit cranial cavity via superior orbital fissure to enter to orbit

Question 8

Abducens CN VI

Answer 8

• motor: lateral rectus
• origin: pons
• exit cranial cavity via superior orbital fissure to enter to orbit

Question 9

Spinal Accessory CN XI

Answer 9

• motor: trapezius and sternocleidomastoid
• origin: rootlets at cervical region of spinal cord
• enters cranium through foramen magnum, exits again via jugular foramen

Question 10

Hypoglossal CN XII

Answer 10

• motor: tongue muscles
• origin: medulla oblongata
• exits cranium via hypoglossal canal

Question 11

Trigeminal CN V

Answer 11

3 divisions
- ophthalmic: V1
- Maxillary: V2
- Mandibular: V3

• motor: V3 only, muscles of mastication
• sensory: all three, somatic sensory for face, oral cavity, nasal cavity, anterior 2/3 of tongue (not taste)
• origin: pons
• transits cranial cavity via superior orbital fissure (V1), foramen rotundum (V2), and foramen ovale (V3)

Question 12

Facial CN VII

Answer 12

• somatic motor: muscles of facial expression
• visceral motor: lacrimal gland, submandibular and sublingual glands
• sensory: taste (anterior 2/3 of tongue)
• origin: pons
• transits cranial cavity via internal auditory meatus and stylomastoid foramen

Question 13

Glossopharyngeal CN IX

Answer 13

• somatic motor: stylopharyngeus
• visceral motor: parotid salivary gland
• sensory: general sensory and taste posterior 1/3 of tongue
• origin: medulla oblongata
• transits cranial cavity via jugular foramen

Question 14

Vagus CN X

Answer 14

• somatic motor: larynx and pharyngeal muscles
• visceral motor: thoracoabdominal viscera - intestines; regulates heart rate; breathing and digestive system activity
• sensory: larynx and most thoracoabdominal viscera, ear canal, pharynx
• origin: medulla oblongata
• transits cranial cavity via jugular foramen

Question 15

Eye

Answer 15

• cornea is protective layer
• superior palpebra (upper eyelid) is lifted by levator palpebrae superioris muscle
• iris controls the amount of light entering eye by determining size of pupil
• sclera is the white of the eye

Question 16

Lens and associated structures

Answer 16

• ciliary muscles change the shape of the lens to allow focusing
• ciliary body produces aqueous human

Question 17

Lacrimal apparatus

Answer 17

• lacrimal gland produces tears to moisten eye
• tears drain into nasolacrimal duct which drains into nasal cavity

Question 18

Ear

Answer 18

3 parts
- external
- middle
- inner

• ear located within petrous portion of temporal bone

Question 19

Middle ear

Answer 19

• tympanic cavity contains three auditory ossicles: Malleus, Incus, and Stapes
• Pharyngotympanic tube connects middle ear and pharynx and equalizes pressure on tympanic membrane

Question 20

Inner Ear

Answer 20

• cochlea converts sound vibrations to nerve impulses which travel to brain via vestibulocochlear nerve
• vestibular structures are responsible for balance: semicircular canals and vestibule (utricle and saccule)

Question 21

Innervation of the tongue

Answer 21

Taste Innervation
- Vagus, Glossopharyngeal, and Facial

Somatic Sensory Innervation
- Vagus, Glossopharyngeal, and Trigeminal