Cranial Nerves

Question 1

What are Cranial Nerves?

Answer 1

What are Cranial Nerves? • 12 nerves that branch off the surface of the brain to innervate the head and neck • Serve sensory, motor, and autonomic functions • CN I and II are located entirely within the CNS (because they don’t leave the skull). Myelinated by Olgiodendrocytes • CN III - XII leave the skull, so have components in both PNS and CNS. Myelinated by Schwann Cells and Oligodendrocytes • What are the implications of this (think clinical pathologies we talked about)? Two MS affects CNS and any cranial nerves (vision from cranial nerve 2) and GB only affect 3-12 that leave the skull but will never affect 1-2.

Question 2

CN I: Olfactory Nerve

Answer 2

-Forms from the medial parahippocampal gyrus (what is located here?) Uncus • Purely sensory (smell) (Carinal nerve 1) • Neurites from olfactory bulb travel down through the into the curvon plate olfactory epithelium within the nose

Question 3

CN II: Optic Nerve

Answer 3

-Nerves that bring visual information from the retina to the thalamus (what is the function of the thalamus?) - relay center take info from the optic nerves and send it to the primarly visual cortex -Some visual information stays laterized, while others informations crosses at the optic chiasm -Purely Senosry -Enters the skull through the Optic Canal

Question 4

CN III Oculomotor Nerve

Answer 4

Originates from the midline of the midbrain, just above the junction between the midbrain and pons • Exits skull through Superior Orbital Fissure

Question 5

CN III Oculomotor Nerve

Answer 5

Motor and Autonomic functions - involved in pupil dilation • Controls: - Levator Palpebrae (lifts eyelid) - Superior Rectus (eyeball elevation) - Medial Rectus (eyeball medially) - Inferior Rectus (eyeball depression) - Inferior Oblique (eye ball up and out)

Question 6

CN IV: Trochlear Nerve

Answer 6

Purely Motor -Emerges dorsally from the midbrain, exits skull through Superior Orbital Fissure -Only controls the superior oblique muscles (eyeball down and out)

Question 7

CN V: Trigeminal Nerve

Answer 7

Both Sensory and Motor Very large - muscles in the face • 3 branches: Ophthalmic (V1), Maxillary (V2), and Mandibular (V3) • Branches off the pons, Ophthalmic exits through Superior Orbital Fissure a branch of VI will enter the skin of the face via the supraobrital notch Maxillary exits through Foramen Rotundum, a branch of v2 will enter the skin of the face via the infraorbital foramen Mandibular exits through Foramen Ovale, a branch of v3 will enter the skin of the face via the mental foramen

Question 8

Motor Control by CN V

Answer 8

The Mandibular (V3) branch provides motor innervation to: - Temporalis Muscle (temporal) - Masseter Muscle (chewing) (zygomatic bone) To assist with chewing and helps elevate the jaw

Question 9

Lesions to CN V

Answer 9

They run on an angle, If you damage CN V, the mandibular branch bc the muscles on the right side push towards the midline then the left side will overpower and jaw divation to the weak side

Question 10

CN VI – Abducens

Answer 10

Purely motor, controls the lateral rectus muscle (abducts the eye) further from the eye • Branches off the brainstem at the midline at the ponto-medullary junction • Exits the skull through Superior Orbital Fissure

Question 11

CN VII: Facial Nerve

Answer 11

Has Sensory, Motor, and Autonomic functions • Motor innervation to: - Muscles of facial expression, smiling, raised eyebrows - Orbicularis oris (closes lips) - Orbicularis oculi (closes eyelids) • Sensory innervation to: - tongue (taste for anterior 2/3) (starbrust example) - pharynx (mouth) - ear canal (qtip in ear) • Exits skull through internal acoustic meatus

Question 12

CN VIII: Vestibulocochlear

Answer 12

Hearing and balance Purely Sensory coming from inner ear • Two branches: Vestibular (head position) and Cochlear (hearing) • Innervation of the labyrinth of the inner ear Problems: ppl will experience vertigo • Enters the skull through internal acoustic meatus

Question 13

CN IX: Glossopharyngeal

Answer 13

Has Sensory, Motor, and Autonomic functions -Involved with our gag reflex • Sensory: - Soft Palate - Pharynx - Taste for posterior 1/3 of the tongue • Motor: - Stylopharyngeus Muscle (important for swallowing) moves food back to mouth • Branches off the medulla posterior to the olives, exits skull through the jugular foramen

Question 14

CN X: Vagus Nerve (wonderer)

Answer 14

Sensory, Motor, and Autonomic functions • Arises just posterior to the olives and inferior to CN IX • Motor: variety of muscles in the pharynx and larynx – swallowing and speaking • Sensory: information from viscera, larynx, and pharynx -Involved in taste • Exits skull through the jugular foramen

Question 15

Damaged to CN X: Vagus Nerve

Answer 15

It’s going to PULL the muscles of the Uvula (dangling part) deviate to the stronger side So if Uvula deviates towards the strong side (the right side) means left there’s a left deficient

Question 16

Cranial Nerve XI: Spinal Accessory

Answer 16

Purely Motor • Innervates the upper trapezius and the sternocleidomastoid (SCM) muscles • Cell bodies are actually in the ventral horn of C1-4; they travel from the cervical cord up through the foreman magnum and out through the jugular foramen

Question 17

Cranial Nerve XI: Spinal Accessory 2

Answer 17

Upper trapezius does shoulder elevation and proxy CN XI nerve Damaged CN XI nerve on the right you’ll have problems strugging shoulders on the right but not left Sternocleidomastiod muscle - sternum, calvicle and mastoid process (contralateal rotates your head)

Question 18

CN XII: Hypoglossal

Answer 18

Purely Motor • Innervates muscles of the tongue for speaking and swallowing • Branches off the medulla between the olive and pyramids • Exits the skull through the Hypoglossal canal

Question 19

Damaged to CN XII: Hypoglossal

Answer 19

Tongue will deviate towards the weak side Tongue’s deviating to the left means left side is damaged

Question 20

Which cranial nerves work together for speech?

Answer 20

Jaw CN V (speech of the jaw), CN VII (move the lips) CN X (innervate vocal cords), CN XII (movement of the tongue)

Question 21

• Which cranial nerves work together for eating/swallowing?

Answer 21

CN V Chewing, CN VII (closing lips), CN IX (move food back to mouth), CN X (innervates muscles in throat for swallowing) CN XII (tongue to break food)