2. An Introduction to the Brain and Cranial Nerves
Learning Outcomes
Describe representative examples of cranial reflexes that produce somatic responses or visceral responses to specific stimuli.

3. 14-10 Cranial Nerves Cranial Nerves
12 pairs connected to brain
Four Classifications of Cranial Nerves
Sensory nerves: carriers of somatic sensory information, including touch, pressure, vibration, temperature, and pain
Special sensory nerves: carriers of sensations such as smell, sight, hearing, and balance
Motor nerves: axons of somatic motor neurons
Mixed nerves: mixture of motor and sensory fibers

4. 14-10 Cranial Nerves Cranial Nerves
Are classified by primary functions
May also have important secondary functions
Distributing autonomic fibers to peripheral ganglia
The 12 cranial nerve groups are identified by:
Primary function
Origin
Pathway
Destination

5. Figure 14-19 Origins of the Cranial Nerves (Part 1 of 2).
Olfactory bulb: termination of olfactory nerve (N I)
Olfactory tract
Optic nerve (N II)
Infundibulum
Oculomotor nerve (N III)
Basilar artery
Pons
Vertebral artery
Medulla oblongata
Cerebellum
Spinal cord

6. Figure 14-19 Origins of the Cranial Nerves (Part 2 of 2).
Optic chiasm
Optic tract
Mammillary body
Trochlear nerve (N IV)
Trigeminal nerve (N V)
Abducens nerve (N VI)
Facial nerve (N VII)
Vestibulocochlear nerve (N VIII)
Glossopharyngeal nerve (N IX)
Vagus nerve (N X)
Hypoglossal nerve (N XII)
Accessory nerve (N XI)

7. 14-10 Cranial Nerves Olfactory Nerves (I) Primary function: Origin:
Special sensory (smell)
Origin:
Receptors of olfactory epithelium
Pathway:
Olfactory foramina in cribriform plate of ethmoid
Destination:
Olfactory bulbs

8. 14-10 Cranial Nerves Olfactory Nerve Structures Olfactory bulbs
Located on either side of crista galli
Olfactory tracts
Axons of postsynaptic neurons
Leading to cerebrum

9. Figure 14-20 The Olfactory Nerve.
Olfactory tract (to olfactory cortex of cerebrum)
Left olfactory bulb (termination of olfactory nerve)
Olfactory nerve (N I)
Olfactory nerve fibers
Cribriform plate of ethmoid bone
Olfactory epithelium

10. 14-10 Cranial Nerves Optic Nerves (II) Primary function: Origin:
Special sensory (vision)
Origin:
Retina of eye
Pathway:
Optic canals of sphenoid
Destination:
Diencephalon via optic chiasm

11. 14-10 Cranial Nerves Optic Nerve Structures Optic chiasm Optic tracts
Where sensory fibers converge
And cross to opposite side of brain
Optic tracts
Reorganized axons
Leading to lateral geniculate nuclei

12. Figure 14-21 The Optic Nerve.
Eye
Pituitary gland
Olfactory bulb
Olfactory tract
Optic nerve (N II)
Optic chiasm
Optic tract
Lateral geniculate nucleus (in thalamus)
Midbrain (cut)
Visual cortex (in occipital lobes)
Optic projection fibers

13. 14-10 Cranial Nerves Oculomotor Nerves (III) Primary function: Origin:
Motor (eye movements)
Origin:
Midbrain
Pathway:
Superior orbital fissures of sphenoid

14. 14-10 Cranial Nerves Oculomotor Nerves (III) Destination:
Somatic motor
Superior, inferior, and medial rectus muscles
Inferior oblique muscle
Levator palpebrae superioris muscle
Visceral motor
Intrinsic eye muscles

15. 14-10 Cranial Nerves Oculomotor Nerve Structures Oculomotor nerve
Controls four of six eye-movement muscles
Delivers autonomic fibers to ciliary ganglion
Ciliary ganglion controls intrinsic muscles of iris and lens

16. 14-10 Cranial Nerves The Trochlear Nerves (IV) Primary function:
Motor (eye movements)
Origin:
Midbrain
Pathway:
Superior orbital fissure of sphenoid
Destination:
Superior oblique muscle

17. 14-10 Cranial Nerves The Abducens Nerves (VI) Primary function:
Motor (eye movements)
Origin:
Pons
Pathway:
Superior orbital fissures of sphenoid
Destination:
Lateral rectus muscle

18. Figure 14-22 Cranial Nerves Controlling the Extrinsic Eye Muscles.
Superior rectus muscle
Optic nerve (N II)
Optic chiasm
Oculomotor nerve (N III)
Trochlear nerve (N IV)
Superior oblique muscle
Trochlea
Levator palpebrae superioris muscle
Trigeminal
nerve (N V), cut
Inferior oblique muscle
Vestibulocochlear nerve (N VIII), cut
Facial nerve (N VII), cut
Inferior rectus muscle
Medial rectus muscle
Ciliary ganglion
Lateral rectus muscle (cut)
Abducens nerve (N VI)

19. 14-10 Cranial Nerves The Trigeminal Nerves (V) Primary function:
Mixed (sensory and motor) to face
Origin:
Ophthalmic branch (sensory)
Orbital structures
Nasal cavity
Skin of forehead, upper eyelid, and eyebrow
Part of nose

20. 14-10 Cranial Nerves The Trigeminal Nerves (V) Origin:
Maxillary branch (sensory)
Lower eyelid
Upper lip, gums, and teeth
Cheek and nose
Palate and part of pharynx

21. 14-10 Cranial Nerves The Trigeminal Nerves (V) Origin:
Mandibular branch (sensory)
Lower gums, teeth, and lips
Palate and part of tongue
Mandibular branch (motor)
Motor nuclei of pons

22. 14-10 Cranial Nerves The Trigeminal Nerves (V) Pathway:
Ophthalmic branch
Superior orbital fissure
Maxillary branch
Foramen rotundum
Mandibular branch
Foramen ovale

23. 14-10 Cranial Nerves The Trigeminal Nerves (V) Destination:
Sensory nerves
Sensory nuclei in pons
Motor nerves of mandibular branch
Muscles of mastication

24. 14-10 Cranial Nerves Trigeminal Nerve Structures Trigeminal nerves
Largest cranial nerves
With three major branches
Semilunar ganglion
Contains cell bodies of sensory neurons

25. Figure 14-23 The Trigeminal Nerve.
Superior orbital fissure
Ophthalmic branch
Supraorbital nerves
Semilunar ganglion
Ciliary ganglion
Pons
Trigeminal nerve (N V)
Foramen rotundum
Maxillary branch
Infraorbital nerve
Foramen ovale
Otic ganglion
Lingual nerve
Submandibular ganglion
Mandibular branch
Mental nerve
Pterygopalatine ganglion

26. 14-10 Cranial Nerves The Facial Nerves (VII) Primary function: Origin:
Mixed (sensory and motor) to face
Origin:
Sensory
Taste receptors on anterior 2/3 of tongue
Motor
Motor nuclei of pons
Pathway:
Internal acoustic meatus to facial canals (stylomastoid foramina)

27. 14-10 Cranial Nerves The Facial Nerves (VII) Destination: Sensory
Sensory nuclei of pons
Somatic motor
Muscles of facial expression
Visceral motor
Tear and nasal mucous glands
Submandibular and sublingual salivary glands

28. 14-10 Cranial Nerves Facial Nerve Structures Facial nerve branches
Temporal
Zygomatic
Buccal
Mandibular
Cervical branches

29. 14-10 Cranial Nerves Facial Nerve Structures Geniculate ganglia
Hold cell bodies of sensory neurons
Pterygopalatine ganglia
Postganglionic fibers innervate glands (lacrimal, nasal cavity, and pharynx)
Submandibular ganglia
Innervate salivary glands

30. Figure 14-24a The Facial Nerve.
Pterygopalatine ganglion
Greater petrosal nerve
Geniculate ganglion
Facial nerve (N VII)
Temporal branch
Pons
Zygomatic branches
Posterior auricular branch
Buccal branch
Stylomastoid foramen
Chorda tympani nerve (with mandibular branch of N V)
Mandibular branch
Lingual branch (with lingual nerve of N V)
Cervical branch
Submandibular ganglion a
The origin and branches of the facial nerve

31. Figure 14-24b The Facial Nerve.
Temporal branch
Zygomatic branch
Buccal branch
Mandibular branch
Cervical branch b
The superficial distribution of the five major branches of the facial nerve

32. 14-10 Cranial Nerves The Vestibulocochlear Nerves (VIII)
Primary function:
Special sensory
Vestibular branch
Balance and equilibrium
Cochlear branch
Hearing

33. 14-10 Cranial Nerves The Vestibulocochlear Nerves (VIII) Origin:
Receptors of inner ear
Pathway:
Internal acoustic meatus of temporal bones
Destination:
Vestibular and cochlear nuclei of pons and medulla oblongata

34. 14-10 Cranial Nerves Vestibulocochlear Nerve Structures
Vestibular branch
Originates at receptors of vestibule (balance)
Connects to vestibular nuclei of pons and medulla oblongata
Cochlear branch
Originates at sensors of cochlea (hearing)
Connects with cochlear nuclei of pons and medulla oblongata

35. Figure 14-25 The Vestibulocochlear Nerve.
Tympanic cavity (middle ear)
Semicircular canals
Vestibular branch (N VIII)
Facial nerve (N VII), cut
Internal acoustic meatus
Vestibulocochlear nerve (N VIII)
N V
Pons
N VI
N VII
N IX
N XII
N X
Medulla oblongata
N XI
Tympanic membrane
Auditory tube
Cochlea
Cochlear branch (N VIII)

36. 14-10 Cranial Nerves The Glossopharyngeal Nerves (IX)
Primary function:
Mixed (sensory and motor) to head and neck

37. 14-10 Cranial Nerves The Glossopharyngeal Nerves (IX) Origins: Sensory
Posterior 1/3 of tongue
Part of pharynx and palate
Carotid arteries
Motor
Motor nuclei of medulla oblongata

38. 14-10 Cranial Nerves The Glossopharyngeal Nerves (IX) Pathway:
Jugular foramina between occipital and temporal bones
Destination:
Sensory
Sensory nuclei of medulla oblongata
Somatic motor
Nerves involved in swallowing
Visceral motor
Parotid salivary gland

39. 14-10 Cranial Nerves Glossopharyngeal Nerve Structures
Superior and inferior ganglion
Sensory neurons of tongue and pharynx
Otic ganglion
Synapse visceral motor fibers

40. Figure 14-26 The Glossopharyngeal Nerve.
Pons
N V
N VII
N VIII
N VI
Glossopharyngeal nerve (N IX)
Otic ganglion
Medulla oblongata
Inferior (petrosal) ganglion
Superior (jugular) ganglion
Pharyngeal branches
Lingual branch
Parotid salivary gland
Carotid sinus branch
Carotid body
Carotid sinus
Common carotid artery

41. 14-10 Cranial Nerves The Vagus Nerves (X) Primary function:
Mixed (sensory and motor)
Widely distributed in thorax and abdomen

42. 14-10 Cranial Nerves The Vagus Nerves (X) Origins: Sensory Motor
Part of pharynx
Auricle and external acoustic meatus
Diaphragm
Visceral organs of thoracic and abdominopelvic cavities
Motor
Motor nuclei in medulla oblongata

43. 14-10 Cranial Nerves The Vagus Nerves (X) Pathway: Jugular foramina
Between occipital and temporal bones

44. 14-10 Cranial Nerves The Vagus Nerves (X) Destination: Sensory
Sensory nuclei and autonomic centers of medulla oblongata
Visceral motor
Muscles of the palate and pharynx
Muscles of the digestive, respiratory, and cardiovascular systems in thoracic and abdominal cavities

45. 14-10 Cranial Nerves Vagus Nerve Structures Vagus nerves
Branch and radiate extensively
Superior (jugular) ganglion and inferior (nodose) ganglion
Hold sensory neurons

46. Figure 14-27 The Vagus Nerve (Part 1 of 2).
Pharyngeal branch
Vagus nerve (N X)
Pons
Medulla oblongata
Auricular branch to external ear
Superior ganglion of vagus nerve
Inferior ganglion of vagus nerve
Pharyngeal branch
Superior laryngeal nerve
Internal branch
Superior laryngeal nerve
External branch

47. Figure 14-27 The Vagus Nerve (Part 2 of 2).
Recurrent laryngeal nerve
Cardiac branches
Cardiac plexus
Right lung
Left lung
Liver
Anterior vagal trunk
Spleen
Stomach
Celiac plexus
Pancreas
Colon
Small intestine
Hypogastric plexus

48. 14-10 Cranial Nerves The Accessory Nerves (XI) Primary function:
Motor to muscles of neck and upper back
Origin:
Motor nuclei of spinal cord and medulla oblongata

49. 14-10 Cranial Nerves The Accessory Nerves (XI) Pathway: Destination:
Jugular foramina between occipital and temporal bones
Destination:
Internal branch
Voluntary muscles of palate, pharynx, and larynx
External branch
Sternocleidomastoid and trapezius muscles

50. 14-10 Cranial Nerves Accessory Nerve Structures Spinal root
Motor fibers that originate in anterior gray horns of first five cervical segments of spinal cord
Cranial root
Motor fibers that originate in medulla oblongata

51. 14-10 Cranial Nerves Accessory Nerve Structures Internal branch
Joins the vagus nerve
External branch
Controls muscles of neck and back

52. 14-10 Cranial Nerves The Hypoglossal Nerves (XII) Primary function:
Motor (tongue movements)
Origin:
Motor nuclei of medulla oblongata
Pathway:
Hypoglossal canals of occipital bone
Destination:
Muscles of tongue

53. Figure 14-28 The Accessory and Hypoglossal Nerves.
Hypoglossal nerve (N XII)
Trigeminal nerve (N V)
Accessory nerve (N XI)
Medulla oblongata
Cranial root of N XI
Internal branch: to palatal, pharyngeal, and laryngeal muscles with vagus nerve
Spinal root of N XI
Intrinsic muscles of tongue
Styloglossus muscle
External branch of N XI
Genioglossus muscle
Geniohyoid muscle
Spinal cord
Hyoglossus muscle
Hyoid bone
Trapezius muscle
Thyrohyoid muscle
Sternocleidomastoid muscle
Sternohyoid muscle
Ansa cervicalis (cervical plexus)
Sternothyroid muscle
Omohyoid muscle

54. Table 14-4 Cranial Nerve Branches and Functions (Part 1 of 2).

55. Table 14-4 Cranial Nerve Branches and Functions (Part 2 of 2).

56. 14-10 Cranial Reflexes Cranial Reflexes
Monosynaptic and polysynaptic reflex arcs
Involve sensory and motor fibers of cranial nerves
Clinically useful to check cranial nerve for brain damage

57. Table 14-5 Cranial Reflexes.