1. HONORS ANATOMY & PHYSIOLOGY
THE CRANIAL NERVES
HONORS
ANATOMY & PHYSIOLOGY

2. CRANIAL NERVES
12-pair
named “cranial” because each passes thru a foramina of the cranium
part of PNS
each with roman numeral (order from anterior  posterior in which nerves arise from base of brain) & a name that indicates nerve distribution

3. CRANIAL NERVES
classified as:
sensory
motor
mixed (sensory & motor)

4. Cranial Nerve I: Olfactory
olfact = to smell
sensory
olfactory epithelium on superior surface of nasal cavity just inferior to cribiform plate of ethmoid bone
olfactory receptors are bipolar neurons
each: single odor-sensitive dendrite
their unmyelinated axons join above plate form rt or lt olfactory nerves

5. Course of Olfactory Nerve
olfactory nerves end in pair of olfactory bulbs: masses of gray matter resting just above cribiform plate where they synapse with next neurons in olfactory pathway

6. Course of Olfactory Nerve
axons of these neurons make up the olfactory tracts  posteriorly to primary olfaction center in temporal lobe

7. Cranial Nerve II: Optic Nerve
optic = eye
sensory
rods & cones in retina: receptors initiating visual signals & relay them  bipolar cells  optic ganglion neurons  their axons join forming optic nerves
pass thru optic foramen  optic chiasm: a cross-over of medial half of each eye to opposite side (lateral half does not cross

8. Optic Chiasm

9. Optic Tracts from optic chiasm  optic tracts
most axons  thalamus  synapse with neurons whose axons  primary visual area of occipital lobe
some axons synapse with motor neurons in midbrain extrinsic eye muscles

10. Cranial Nerve III: Oculomotor
oculo = eye
mixed, mainly motor
its motor nucleus in ventral part of midbrain
2 branches pass thru superior orbital fissure

11. Oculomotor Nerve Extrinsic Muscles of Eye
Superior Branch
Inferior Branch
axons innervate:
superior rectus
levator palpebrae superioris (upper eyelid)
axons innervate:
medial rectus
inferior rectus
inferior oblique

12. Oculomotor Nerve inferior branch also:
parasympathetic innervation to intrisic muscle of eye (smooth muscle)
ciliary muscle: adjusts lens for near/far vision
circular muscle of iris: contracts/relaxes in response to amt of light (pupils constrict/dilate)

15. Oculomotor Nerve: Sensory
proprioception: nonvisual perception of movements & positions of body

16. Cranial Nerve IV: Troclear Nerve
trochle = pulley
mixed, mainly motor
smallest of the 12 cranial nerves
only 1 that arises from posterior of midbrain

17. Cranial Nerve IV: Troclear Nerve
motor:
axons from nucleus in midbrain  superior orbital fissure
innervates superior oblique muscle
sensory: proprioception in superior oblique

18. Cranial Nerve IV: Troclear Nerve

20. Trigeminal Nerve V largest of 12 cranial nerves mixed:
sensory: ganglion in temporal bone
motor: neurons in pons

21. Cranial Nerve V: Trigeminal Nerve
tri: has 3 branches
Ophthalmic: sensory only: upper eyelids, eyes, lacrimal glands, upper nasal cavity, side of nose, forehead, anterior ½ of scalp
Maxillary: sensory only: mucosa of nose, palate, part of pharynx, upper teeth, upper lip, lower eyelids
Mandibular: sensory: anterior 2/3 of tongue (not taste), cheek, lower teeth
motor: muscles of mastication

22. Trigeminal Nerve

23. Cranial Nerve VI: Abducens Nerve
ab: away / ducens: to lead (nerve impulses causes abduction of eyeball)
mixed mainly motor
nucleus in pons (motor): innervates lateral rectus muscle
sensory: proprioception in lateral rectus

24. Abducens Nerve

25. On Which Side is VI not Functioning?

27. Cranial Nerve VII: Facial Nerve
mixed
sensory:
taste buds anterior 2/3 of tongue, proprioceptors in face & scalp
motor:
nucleus in pons
innervates muscles of facial expression + stylohyoid muscle & posterior belly of digastric muscle
parasympathetic: lacrimal glands, palatine glands, salivary glands: sublingual & sub-mandibular

28. Facial Nerve

30. Cranial Nerve VIII: Vestibulocochlear Nerve
vestibule:small cavity; cochlear: snail-like
mixed, mainly sensory
2 branches
Vestibular:
equilibrium
Cochlear:
hearing
motor: hair cells of spiral organ

33. Cranial Nerve IX: Glossopharyngeal Nerve
glosso:tongue, pharyngeal: throat
Mixed
sensory: taste buds & somatic sensory receptors on posterior 1/3 tongue, proprioceptors in swallowing muscles, baroreceptors (stretch) in carotid sinus, chemoreceptors in carotid bodies
motor: from nuclei in medulla, exit thru jugular foramen, innervate stylopharyngeus muscle (elevates pharynx & larynx)
parasympathetic: motor: stimulate parotid gland to secrete saliva

35. Cranial Nerve X: Vagus Nerve
vagus: wanderer, vagrant
mixed
distributed from head  abdomen

36. Vagus Nerve sensory: skin of external ear
taste buds in epiglottis & pharynx
proprioceptors in muscles of neck & throat
baroreceptors in arch of aorta & chemoreceptors in aortic bodies
visceral sensory receptors in most organs of thorax & abdominal cavities

37. Vagus Nerve parasympathetic motor: heart & lungs glands in GI tract
smooth muscle of airways, esophagus, stomach, gall bladder, small intestine, most of large intestine

38. Distribution of Vagus Nerve

40. Cranial Nerve XI: Accessory Nerve
mixed
originates from both the brainstem & spinal cord
cranial root:
motor: from medulla thru jugular foramen
supplies voluntary muscles of pharynx, larynx, & soft palate
spinal root:
mixed, mainly motor
motor:

41. Cranial Nerve XI: Accessory Nerve
spinal root:
mixed, mainly motor
motor: neurons in anterior gray horn of C1 – C5  axons come together  foramen magnum  jugular foramen
innervates sternocleidomastoid & trapezius muscles
sensory: proprioceptors in muscles it supplies

43. Cranial Nerve XII: Hypoglossal
hypo: below, glossal: tongue
mixed
sensory:proprioceptors in tongue muscles  medulla
motor: nucleus in medulla  hypoglossal canal  muscles of the tongue (speech, swallowing)

44. Development of the Nervous System
begins developing in 3rd wk from a thickening of ectoderm called the neural plate

45. Development of the Brain & Spinal Cord