CN VIII-XII

Question 1

CN VIII

Answer 1

Vestibulocochlear n. (composed of vestibular n. and cochlear n.)

Originates in membranous labyrinth of inner ear in petrous temporal bone; leaves petrous temporal bone via internal acoustic meatus along with facial n.

Question 2

Vestibular n.

Answer 2

Part of CN VIII

Transmits afferent impulses to brain relating to pull of gravity and linear/angular acceleration
Receptors (cristae and maculae) in semicircular ducts transmit impulses to vestibular ganglion -> travel along vestibular portion of CN VIII to CNS

Dysfunction - disequilibrium, circling, head tilt of affected side, nystagmus of unaffected side
Tests - Observe gait (should be done blindfolded); righting reflexes

Question 3

Cochlear n.

Answer 3

Part of CN VIII

Responsible for hearing (SSA)
Receptors in spiral organ (Organ of Corti) within cochlea transmit impulses to spiral ganglion -> travel along cochlear portion of CN VIII to CNS

Dysfunction - deafness
Tests - Clap hands or whistle
Genetic deafness in blue-eyed, white cats and dalmatians

Question 4

CN IX

Answer 4

Glossopharyngeal n.

Sensory - caudal portion of tongue, pharyngeal mucosa, carotid sinus (GVA); taste from caudal 1/3 of tongue (SVA)

Motor - stylopharyngeus and other pharyngeal mm. (along w/ CN X) (GSE)

Parasympathetic - to parotid and zygomatic salivary glands (GVE)

Question 5

Sensory of CN IX

Answer 5

Sensory from baroreceptors in wall of carotid sinus and chemoreceptors in carotid body
Sensory from pharyngeal mucosa via pharyngeal br.
Sensory for touch, pain, thermal from caudal 1/3 of tongue via lingual br. (GVA)
Sensory for taste from caudal 1/3 of tongue (SVA)

Dysfunction - hypo/hypertension to head; brady/tachycardia
Test - carotid sinus reflex; inc. pressure on carotid sinus will result in a dec. heart rate (artificially inc. pressure on baroreceptors)

Question 6

Motor of CN IX

Answer 6

Motor to pharyngeal mm. via pharyngeal br. (GSE)

Dysfunction - difficulty swallowing (dysphagia)
Tests - swallowing reflex and gag reflex

Question 7

Pharyngeal plexus

Answer 7

Junction of pharyngeal br. of CN IX and pharyngeal br. of CN X

Supplies motor innervation to pharyngeal mm. and sensory innervation to pharyngeal mucosa

Contains postganglionic sympathetic fibers from cranial cervical ganglion

Question 8

Parasympathetic of CN IX

Answer 8

Innervation of the parotid and zygomatic salivary glands

Dysfunction - partial dryness of mouth

Question 9

CN X

Answer 9

Vagus n.

Sensory - pharynx, larynx, trachea, esophagus, thoracic and abdominal viscera (GVA); external ear canal (GSA); taste to base of tongue and pharynx (SVA)

Motor - muscles of pharynx, larynx, esophagus (GSE)

Parasympathetic - cervical, thoracic, and abdominal viscera