General Concepts Of Cranial Nerves DLA

Question 1

What are the general concepts of nerves?

Answer 1

• 12. pairs. which. are part of peripheral. nervous system

• Formedfromnucleiinthebrain,somefromseveral
• Functionsaredeterminedbynuclei
– Parasympathetic – Sensory
– Motor
• Numberedwithromannumeralsintheordertheyexitthe brain from rostral to caudal
• CNIandIIarecomponentsfromtheforebrain

• CNIII-XII exit from the brainstem(except XI spinal root)
  
  • Ventral: CN III, VI and XII
  • Lateral: CN V and VII-XI (cranial part)
  • Dorsal:CNI

Question 2

What are the Cranial vault divisions and where the nerve passed through the skull?

Answer 2

• Anterior fossa
– CNI

• Middle fossa
– CN II-VI
– divided from the anterior fossa by the lesser wing of the sphenoid

• Posterior fossa
– CNVII-XII
– Divided from the middle fossa by the petrous ridge

Question 3

Why is orientation of the brainstem important?

Answer 3

In order to learn the cranial nerves you need a basic understanding of the brainstem The ventral and dorsal views are most important here
The pons is located in opposition to the clivus of the skull.

It contains majority of CN nuclei
Landmarks: crus cerebri
middle cerebellar peduncles superior & inferior colliculi pontomedullary junction pyramids
olives

Question 4

What are the general concel5s that apply to afferent fibers?

Answer 4

The general arrangement is a three neuron chain
The first (1st order – 1°) arises at the organ and has its cell body located in a ganglion located outside of the CNS, it synapses in the brainstem in the corresponding cranial nerve nucleus

The second (2nd order – 2°) arises from the brainstem nucleus and synapses in the thalamus

The third (3rd order) arises from the thalamus and ends in the cortex

Question 5

What general concept applies to efferent(motor) fibers?

Answer 5

The general arrangement is a two neuron chain The first (upper motor neuron - UMN) arises in the cortex and synapses in the brainstem on the nucleus of the corresponding cranial nerve.

The second (lower motor neuron – LMN) arises from the brainstem nucleus and ends in the muscle it supplies

Question 6

What general cincept applies to parasympathetic efferent fibers?

Answer 6

Similar to motor system but synapeses At parasympathetic ganglion

Question 7

Describe the arrangement of cranial nerve nuclei

Answer 7

The nuclei are arranged in columns according to their nature (motor/sensory/parasympathetic)

• Some cranial nerves (that have multiple functions) share nuclei
• Many of the 12 cranial nerves are interconnected via “reflex
connections”

• Afferent (carrying signal toward brain):
– General:trigeminalnucleus
– Auditoryandbalance/specialorientation:cochlear,vestibularnuclei – Taste:nucleus solitaries

• Efferent (sending signals away from the brain):
– Somatic efferent column: CN III, IV, VI, XII
– Branchiomotor column: CN V, VII, IX (nucleus ambiguus), X (nucleus ambiguus)
– Parasympatheticcolumn:CNIII(Edinger-Westphalnucleus),VII (superior salivatory nucleus), IX (inferior salivatory nucleus), X (dorsal motor nucleus)

Question 8

What is the pathway for parasympathetic nerves going to the ciliary body and sphincter papillae muscles?

Answer 8

Nucleus: Edinger- Westphal

Preganglionic pathway: Oculomotor

Ganglion: ciliary ganglion

Postganglionic: short ciliary

Question 9

What is the pathway for parasympathetic nerves going to the palate, pjarynx, nose, lacrimal?

Answer 9

Nucleus: superior salivatory

Preganglionic pathway: greater petrosal of facial via nerve of pterygoid canal

Ganglion: Pterygopalantine ganglion

Postganglionic pathway: Greater and lesser palantine Nasopalatine lacrimal nerves

Question 10

What is the pathway for parasympathetic nerves going to the sublingual and sub mandibular glands?

Answer 10

Nucleus: superior salivatory

Preganglionic pathway: Chorda tympani via lingual nerve

Ganglion: submandibular ganglion

Postganglionic pathway: lingual nerve

Question 11

What is the pathway for parasympathetic nerves going to the parotid gland?

Answer 11

Nucleus: inferior salivatory

Preganglionic pathway: lesser petrosal and tympanic branches of CN IX

Ganglion: Otic ganglion

Postganglionic pathway: Auriculotemporalnerve

Question 12

What nerves are responsible for sight and smell?

Answer 12

• Smell: CN I (olfactory)

• Sight: CN II (optic)

Question 13

What nerves are responsibke for eyeballl movement?

Answer 13

Eyeball movement: CNIII (oculomotor), IV (trochlear) & VI (abducens)

Question 14

What nerves are responsibke for facial sensation and movement?

Answer 14

Facial sensation & mastication: CN V (trigeminal)
– V1:sensory
– V2:sensory
– V3: sensory & masticatory

Facial expression: CN VII (facial)

Question 15

What nerve is responsible for balance & hearing?

Answer 15

Balance & hearing: CN VIII (vestibulocochlear)

Question 16

What nerves are responsible for taste?

Answer 16

Taste: CN VII (chorda tympani of facial), IX (glossopharyngeal), X (vagus)

Question 17

What nerves are responsible for tongue movement?

Answer 17

Tongue movement: CN XII (hypoglossal)

Question 18

What nerves are responsible for salivation?

Answer 18

• Salivation: CN VII (chorda tympani of facial), IX (lesser petrosal of glossopharyngeal), X (vagus to minor glands)

Question 19

Whaat cranial nerves are parasympathetic?

Answer 19

Parasympathetic: CN III, VII, IX & X

Question 20

What cranial nerve is responsible for shoulder and head movement?

Answer 20

Shoulder and head movement: CN XI (spinal accessory)