2e. Pathways of CNs

Question 1

Pathway: Olfactory N.

Answer 1

• Origin: receptors (bipolar neurons) in olfactory mucosa of nasal cavity
• Travels through foramina in cribriform plate of ethmoid bone
• Synapses in olfactory bulbs (anterior cranial fossa)

Question 2

Pathway: Optic N.

Answer 2

• Origin: retina of the eye
• Enters cranium via optic foramen of sphenoid bone
• Unite at optic chiasm
• Optic tracts travel to lateral geniculate nucleus of thalamus
• Information forwarded to occipital lobe

Question 3

Pathway: Oculomotor N.

Answer 3

• Origin: oculumotor and Edinger Westphal nuclei within mesencephalon
• Leaves cranium via superior orbital fissure
• Travels to eye and eyelid
  
  • Parasympathetic fibers to ciliary ganglion
  • Postganglionic parasympathetic fibers to iris and ciliary muscle

Question 4

Pathway: Trochlear N.

Answer 4

• Origin: trochlear nucleus within mesencephalon
• Leaves cranium via superior orbital fissure
• Travels to superior oblique muscle

Question 5

Pathway: Abducens N.

Answer 5

• Origin: pontine nucleus in pons
• Leaves cranum through superior orbital fissure
• Travels to lateral rectus muscle

Question 6

Pathway: Trigeminal N.

Answer 6

• Origin: pons
• V1: Enters cranium via superior orbital fissure
  
  • Travel to trigeminal ganglion before entering pons
• V2: Enters cranium via foramen rotundum
  
  • Travel to trigeminal ganglion before entering pons
• V3: Motor fibers leave pons and exit cranium via oramen ovale
  
  • Sensory fibers travel through foramen ovale to trigeminal ganglion then pons

Question 7

Pathway: Facial N.

Answer 7

• Origin: nuclei within the pons
• Sensory fibers from tongue via chorda tympani branch of facial n.
  
  • Through tiny foramen to enter skull
  • Synapse at geniculate ganglion of facial n.
• Somatic motor fibers leave pons and enter temporal bone through internal auditory canal
  
  • ​Project through temporal bone
  • Emerge from stylomastoid foramen
• Parasympathetic motor fibers leave pons and enter internal auditory canal
  
  • ​Leave w/ greater petrosal n. or chroda tympani n. and travel to autonomic ganglion before innervating glands

Question 8

Pathway: Glossopharyngeal N.

Answer 8

• Origin: sensory (taste buds and mucosa of post 1/3 of tongue & carotid bodies) and motor (nuclei in medulla oblongata)
• Sensory fibers from origins along nerve through inferior or superior ganglion into jugular foramen then pons
• Somatic motor fibers leave cranium via jugular foramen to stylopharyngeus m.
• Sensory fibers go to post 1/3 tongue and carotid bodies
• Parasympathetic motor fibers to otic ganglion then parotid gland

Question 9

Pathway: Vagus N.

Answer 9

• Origin: motor nuclei in medulla oblongata
• Leaves cranium via jugular foramen traveling and branching in neck, thorax, and abdomen
• Snesory neuron cell bodies located in superior and inferior ganglia assoc with nerve

Question 10

Pathway: Accessory N.

Answer 10

• Motor nuclei in SC
• Spinal roots travel superiorly to enter skull through foramen magnum
• Cranial and spinal roots merge and leave skull via jugular foramen
• Outside skull cranial root splits to travel with CN X
• Spinal roots travel to SCM and trapezius

Question 11

Pathway: Hypoglossal N.

Answer 11

• Origin: hypoglossal nucleus in medulla oblongata
• Leaves cranium via hypoglossal canal then travels inferior to mandible and to inferior surface of tongue

Question 12

Pathway: Vestibulocochlear N.

Answer 12

• Origin: hair cells in vestibule of inner ear and cochlea of inner ear
• Sensory cell bodies of vest branch in vestibular ganglion
• Sensory cell bodies of cochlear branch in spiral ganglion near cochlea
• Branches merge and enter cranial cavity through internal auditory canal
• Travel to junction of pons and medulla oblongata