Cranial Nerves

Question 1

Cranial vs. Spinal Nerves

Answer 1

Cranial nerves come from ventral side of brain/brainstem; only carry parasympathetic modality; get sympathetic modality from spinal nerves; part of CNS

Spinal nerves come out of spinal cord; carry parasympathetic and sympathethic modalities; part of PNS

Question 2

Cranial Nerves that Carry Special Sensory Modalities

Answer 2

1. Smell- CN I (Olfactory)
2. Vision-CN II (Optic)
3. Balance and Hearing; CN VIII-(Vestibulocochlear)
4. Taste/Gustatory- Branches of CN VII( facial), CN IX (glossopharyngeal) and Cranial nerve X( vagus)

Question 3

What are cranial nerves?

Answer 3

12 pairs of nerves
CN I and II come from forebrain

CN III-XII come from brainstem

Mostly innervate head and neck

Contain special sensory modalities ( smell, vision, gustatory,, and balance/hearing)

Have parasympathetic ( CN X) but not sympathetic innervation

Question 4

CN I

Answer 4

Olfactory or Smell

Not a discrete nerve

olfaction receptors found in top of nasal cavity

Question 5

CN II

Answer 5

Optic/Vision

Nerve close to pituitary gland

Question 6

Optic Path

Answer 6

1. Optic nerves ( L and R) come together at optic chiasm

2. After optic chiasm the optic nerves split and become the optic tract

Question 7

How visual field organized_____

Answer 7

1. lateral side of retina will see central vision and the medial part of retina will see the outer part of vision ( peripheral vision)
2. the medial retina crosses over to opposite side ( contralateral) of brain through the optic chiasm
3. the lateral retina doesn’t crossover at optic chiasm; it stays to the same side after passing optic chiasm ( ipsilateral)

Question 8

Hemianopsia

Answer 8

Temporal/peripheral vision lost with optic chiasm lesions

Question 9

CN III, CN IV, and CN VI

Answer 9

Nerves involved in eye movement
has PNS, SNS, somatic motor, and visceral motor innervation

CN III-Oculomotor

CN IV-Trochlear

CN VI-Abducens

Question 10

CN V

Answer 10

Trigeminal

major sensoroy nerve of face and motor innervation to some skeletal muscles

Divided in 3 branches: V1 ( ophthalmic), V2 ( maxillary) and V3 ( mandibular)

Question 11

CN VII

Answer 11

Facial

motor innervation to facial expression muscles and most glands, taste from front of tongue

Complex Intracranial and extracranial path

Question 12

Facial Weakness Test

Answer 12

A clinicial test that can differ b/w PNS or CNS damage

PNS-total facial droop of one side of face ( bell’s palsy)

CNS- both side of forehead region only is functional and rest of affected side of face had droop

Question 13

CN VIII

Answer 13

Vestibulocochlear

Carries two special sensory modalities:

1. Vestibular
2. Cochlear

Question 14

CN IX

Answer 14

Glossopharygneal

Has general sensory, visceral sensory, special sensory, and motor modalities related to tongue and other structures in mouth

Question 15

CN X

Answer 15

Vagus

Has general sensory, visceral sensory, PNS, and somatic motor modalities

Question 16

CN XI

Answer 16

Spinal accessory

Not really a CN, travels with CN X

Question 17

CN XII

Answer 17

Hypogloassal

Somatic motor innervation of intrinsic and extrinsic tongue muscles

Question 18

Parasympathetic Ganglia

Answer 18

Ganglia=contains cell body of peripheral nerves and is meeting place of two nerves

Involves a pre-ganglionic nerve ( long) and a post-ganglion nerve ( short)

Question 19

How to Assess function of CNs in Clinical Exam

Answer 19

Simple Clinical Test that is used to measure CNs dys/function:

CN 1 Smell mint
CN 2 Look straight ahead=can you see
CN 3, 4,6= head immobile but eyes move , tracing H; parasymapthetics for 3,shine light
CN 5 touch=temporal, cheek, and jaw ( three branches)
CN 7=make expressions
CN 8=can you hear; balance test
CN 9=stick something in back of thoart ( can be uncomfortable
CN 10=no autonomic, swalling, speaking
CN 11=raise shoulder, head side to side
CN 12=stick out tongue (