Exam 4 Cranial Nerves

Question 1

Cranial Nerve Motor Nuclei

• What spinal cord fiber types originate here?
• What do these nerves innervate?
• What is this nuclei equivalent to in the spinal cord?

Answer 1

• Somatic motor fibers
• Innervate skeletal muscles of face and neck
• Equivalent to ventral horn of spinal cord

Question 2

Cranial Nerve Sensory Ganglia

• What is this equivalent to in the spinal cord?
• What are its components?
• What is the cranial nerve sensory nucleus equivalent to in the spinal cord?

Answer 2

• Equivalent to spinal ganglia
• Parts:
  
  • Peripheral process (associated with receptor)
  • Central process (from ganglion to cranial nerve sensory nucleus)
• Cranial nerve sensory nucleus equivalent to dorsal horn in spinal cord

Question 3

Cranial Parasympathetics

• What cranial nerves have parasympathetic nuclei?
• What are these nuclei equivalent to in the spinal cord?
• What is different between parasympathetics in the head and neck verses the rest of the body?

Answer 3

• CN III, VII, IX, X have parasympathetic nuclei
• These nuclei are equivalent to lateral horn of gray matter in S2-4
• Preganglionic parasympathetics must synapse in a parasympathetic ganglion in the head and neck, whereas parasympathetics in the rest of the body synapse within the wall of the organ.

Question 4

• What are the parasympathetic ganglia?

Answer 4

• Ciliary (CN III)
• Otic (CN IX)
• Pterygopalantine (CN VII)
• Submandibular (CN VII)

“COPS” ganglia

Question 5

• How do postganglionic parasympathetics reach their targets?
• How do postganglionic sympathetics reach their targets?

Answer 5

• Parasympathetics: Via branches of CN V (trigeminal nerve)
• Sympathetics:
  
  • Follow external carotid artery to reach target organs
  • Follow internal carotid artery -> branches of trigeminal system -> target organs
  • Travel on their own before joining with other nerves

ALL sympathetic fibers in the head are postganglionic.

Question 6

• How do preganglionic parasympathetics reach their targets?
• How do preganglionic sympathetics reach their targets?

Answer 6

• Parasympathetics: Via branches of CN III, VII, or IX
• Sympathetics: Originate in T1-4 of IML and ascend to terminate in superior cervical ganglion.

Question 7

Olfactory nerve (CN I)

• What type of nerve fibers are found in this nerve?
• What opening does this nerve pass through?
• Where do these axons originate/terminate?

Answer 7

• Sensory nerve fibers
• Pass through openings in cribiform plate of ethmoid bone
• Cells are bipolar with axons originating in nasal epithelium and terminating in olfactory bulb/tract of brain.

Question 8

Optic nerve (CN II)

• What type of nerve fiber types are found in this nerve?
• What opening does it pass through?
• What is the optic chiasm? What projects from optic chiasm?

Answer 8

• Sensory nerve fibers (ganglion cells of retina)
• Passes through optic canal
• Optic chiasm: formed by union of two optic nerves
  
  • Some retinal fibers may cross to other side here
  • Optic tracts project from chiasm posteriorly to thalamus

Question 9

Vestibulocochlear (CN VIII)

• What nerve fiber types are found in this nerve?
• What opening does it pass through?
• What nerves does it split into and what is their function?
• Where are the nerve bodies of these nerves located?
  
  • Where are central and peripheral processes located?

Answer 9

• Sensory nerve fibers
• Passes through internal acoustic meatus
• Splits into vestibular nerve (senses balance) and cochlear nerve (senses hearing) in temporal bone
• Vestibular cell bodies located in vestibular ganglion
  
  • Send central processes into vestibular nuclei
  • Send peripheral processes to vestibular apparatus
• Cochlear cell bodies located in cochlear (spiral) ganglia
  
  • Send central processes into cochlear nuclei
  • Send peripheral processes into cochlea

Question 10

Occulomotor nerve (CN III)

• What type of nerve fibers are found in this nerve?
• What opening does it pass through?
• What does this nerve innervate?
• Where are its cell bodies located?

Answer 10

• Somatic motor and parasympathetic fibers
• Passes from midbrain through superior orbital fissure to orbital
• Innervation: Somatic to all extraocular muscles except lateral rectus and superior oblique. (Also innervates levator palpebrae superioris)
  
  • Parasympathetics innervate sphincter pupillae and ciliaris
• Cell body locations: Somatic located in oculomotor nucleus
  
  • Preganglionic parasympathetic bodies located in Edinger Westfall nucleus -> preganglionic fibers synapse in ciliary ganglion -> postganglionic fibers travel to eye via short ciliary nerves

Question 11

Trochlear nerve (CN IV)

• What type of nerve fibers are found in this nerve?
• What opening does it pass through?
• What does it innervate?
• Where are its cell bodies located?

Answer 11

• Only somatic motor fibers
• Passes through superior orbital fissure
• Innervates superior oblique muscle
• Cell bodies located in trochlear nucleus of pons

Question 12

Abducens nerve (CN VI)

• What nerve fiber types are found in this nerve?
• What opening does it pass through?
• What does it innervate?
• Where are its cell bodies located?

Answer 12

• Only somatic motor fibers
• Passes through superior orbital fissure (after passing through cavernous sinus)
• Innervates lateral rectus muscle
• Cell bodies located in abducens nucleus

Question 13

Spinal accessory nerve (CN XI)

• What nerve fiber types are found in this nerve?
• What does it innervate?
• What opening does it pass through?
• Where are its cell bodies located?

Answer 13

• Only somatic motor fibers
• Innervates trapezius and sternocleidomastoid
• Passes through jugular foramen (after entering skull through foramen magnum)
• Cell bodies located in spinal accessory nucleus (in upper 5 segments of spinal cord)

Question 14

Hypoglossal nerve (XII)

• What types of nerve fibers are found in this nerve?
• What does it innervate?
• What opening does it pass through?
• Where are its cell bodies located?

Answer 14

• Only somatic motor fibers
• Innervates all intrinsic and extrinsic musculature in tongue except palatoglossus
• Passes through hypoglossal canal (loops around occipitial artery to enter lateral side of tongue)
• Cell bodies located in hypoglossal nucleus

Question 15

Trigeminal nerve (CN V)

• What are its branches?
• What type of nerve fibers are found in this nerve?
• What does it innervate?
• Where are its cell bodies located?
• What opening does it pass through?

Answer 15

• Branches: Ophthalmic (V1), Maxillary (V2), Mandibular (V3)
• Somatic motor and somatic sensory found in this nerve fiber
• Innervate skin of face and underlying structures (see facial map for distribution)
• Cell bodies for sensory fibers located in Trigeminal Ganglion
  
  • Cell bodies for motor fibers innervating eight muscles located in Trigeminal Motor Nucleus
• Openings it passes through:
  
  • Ophthalmic: Superior orbital fissure
  • Maxillary: Foramen rotundum
  • Mandibular: Foramen ovale

Question 16

Facial nerve (CN VII)

• What type of nerve fibers are located in this nerve?
• What does it innervate?
• Where are its cell bodies located?
• What opening does it pass through?

Answer 16

Nerve fiber types:

• Somatic motor fibers:
  
  • Innervate muscles of facial expression, stapedius, stylohyoid, and posterior belly of digastric mm
  • Cell bodies located in facial motor nucleus
• Preganglionic parasympathetic fibers:
  
  • Innervate lacrimal gland, submandibular gland, nasal mucosal glands, and oral muscosal glands
  • Cell bodies located in superior salivary nucleus (synapse in either pterygopalantine or submandibular ganglion)
• Somatic sensory fibers:
  
  • Innervate external ear and anterior 2/3 of tongue (via taste fibers)
  • Cell bodies located in geniculate ganglion
• All fibers of facial nerve exit cranial cavity through the internal acoustic meatus

Question 17

• The somatic motor and sensory fibers of the facial nerve take a sharp turn in…
• And exit at the…

Answer 17

• the facial canal of temporal bone
• stylomastoid foramen

Question 18

• Within the temporal bone, the facial nerve gives off what two nerves?
• What are their fiber types?
• Where do they synapse?

Answer 18

• Greater petrosal nerve
  
  • Preganglionic parasympathetic fibers
  • Synapse in pterygopalatine ganglion
• Chorda tympani
  
  • Preganglionic parasympathetic and taste fibers
  • Synapse in sybmandibular ganglion

Question 19

The pterygopalatine ganglion innervates…

Answer 19

• Lacrimal gland
• Nasal mucosa
• Palatal mucosa

JBC calls it the “Hay fever ganglion”

Question 20

The submandibular ganglion innervates…

Answer 20

• Submandibular glands
• Sublingual salivary glands

Question 21

Glossopharyngeal nerve (CN IX)

• What type of nerve fibers are found in this nerve?
• What does it innervate?
• Where are the cell bodies located?
• What opening does it pass through?

Answer 21

Nerve fiber types:

• Somatic motor fibers:
  
  • Innervate stylopharyngeus muscle
  • Cell bodies located in nucleus ambiguous ganglion
• Parasympathetic fibers:
  
  • Innervate parotid gland to stimulate secretion
  • Cell body located in inferior salivary nucleus -> fibers pass via lesser petrosal n to otic ganglion
• Somatic sensory fibers:
  
  • Carry pain, temperature, taste, and touch impulses from the posterior 1/3 of the tongue, tonsils, soft palate, and sides of pharynx
  • Cell bodies located in inferior ganglion of IX
• Visceral sensory fibers:
  
  • Innervate carotid sinus (baroreceptor) and carotid body (chemoreceptor) on internal carotid artery
  • Cell bodies are located in inferior ganglion of IX

All fibers pass through jugular foramen.

Question 22

Vagus nerve (CN X)

• What type of nerve fibers are found in this nerve?
• What do they innervate?
• Where are the cell bodies located?
• What opening do they pass through?

Answer 22

Nerve fiber types:

• Preganglionic parasympathetic fibers:
  
  • Give off branches to thorax and abdomen as far along as splenic flexure
  • Cell bodies located in dorsal motor nucleus of vagus. Synapse in intramural ganglia in wall of organ
• Somatic motor fibers:
  
  • Innervate skeletal muscles of pharynx, larynx, and palate
  • Cell bodies located in nucleus ambiguous
• General somatic sensory fibers:
  
  • Innervate external ear and external tympanic membrane
  • Cell bodies located in superior (jugular) ganglion of X
  • Taste fibers from epiglottis cell bodies located in inferior ganglion
• Visceral sensory fibers:
  
  • Innervate larynx, pharynx, thorax, and abdomen
  • Cell bodies located in inferior (nodose) ganglion of X

All nerve fibers exit through jugular foramen.