The Cranial Nerves Honors Anatomy & Physiology - PowerPoint Presentation

Slide1

The Cranial Nerves

Honors Anatomy & Physiology

for copying

Slide2

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

Slide3

CRANIAL NERVES

classified as:

sensory

motor

mixed (sensory & motor)

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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

Slide5

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

Slide6

Course of Olfactory Nerve

axons of these neurons make up the

olfactory tracts



posteriorly to primary olfaction center in temporal lobe

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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

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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

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Cranial Nerve III: Oculomotor

oculo

= eye

mixed, mainly motor

its motor nucleus in ventral part of midbrain

2 branches pass thru superior orbital fissure

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Superior Branch

Inferior Branch

axons innervate:

superior rectus

levator

palpebrae

superioris

(upper eyelid)

axons innervate:

medial rectus

inferior rectus

inferior oblique

Oculomotor

Nerve

 Extrinsic Muscles of Eye

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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)

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Oculomotor Nerve: Sensory

proprioception

:

nonvisual

perception of movements & positions of body

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Cranial Nerve IV: Troclear Nerve

trochle

= pulley

mixed, mainly motor

smallest of the 12 cranial nerves

only 1 that arises from posterior of midbrain

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Cranial Nerve IV: Troclear Nerve

motor

:

axons from nucleus in midbrain

 superior orbital fissure

innervates superior oblique muscle

sensory:

proprioception

in superior oblique

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Trigeminal Nerve

largest of 12 cranial nerves

mixed:

sensory: ganglion in temporal bone

motor: neurons in

pons

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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

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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

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Cranial Nerve VII: Facial Nerve

mixed

sensory:

taste buds anterior 2/3 of tongue,

proprioceptors

in face & scalpmotor:

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

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Cranial Nerve VIII: Vestibulocochlear Nerve

vestibule:

small

cavity;

cochlear

: snail-likemixed, mainly sensory

2 branches

Vestibular:

equilibrium

Cochlear:

hearing

motor: hair cells of spiral organ

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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

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Cranial Nerve X: Vagus Nerve

vagus

: wanderer, vagrant

mixed

distributed from head

 abdomen

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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

Slide23

Vagus Nerve

parasympathetic motor:

heart & lungs

glands in GI tract

smooth muscle of airways, esophagus, stomach, gall bladder, small intestine, most of large intestine

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Cranial Nerve XI: Accessory Nerve

mixed

originates from

both

the brainstem & spinal cord

cranial root:motor: from medulla thru jugular foramensupplies voluntary muscles of pharynx, larynx, & soft palate

spinal root:

mixed, mainly motor

motor:

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Cranial Nerve XI: Accessory Nerve

spinal root:

mixed, mainly motor

motor: neurons in anterior gray horn of C1 – C5

 axons come together 

fpramen

magnum  jugular foramen

innervates

sternocleidomastoid

&

trapezius

muscles

sensory:

proprioceptors

in muscles it supplies

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Cranial Nerve XII: Hypoglossal

hypo:

below,

glossal

: tongue

mixedsensory:proprioceptors in tongue muscles  medulla

motor: nucleus in medulla  hypoglossal canal  muscles of the tongue (speech, swallowing)

Slide27

Development of the Nervous System

begins developing in 3

rd

wk from a thickening of ectoderm called the neural plate

Slide28

Development of the Brain & Spinal Cord