BIOL110 Lecture Notes - Jugular Foramen, Stylopharyngeus Muscle, Inferior Petrosal Sinus

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30 Jan 2013
Cranial Nerves Lectures I and II
CN I = olfactory
Special sensory nerve of smell
Olfactory nerve = bundle of nerves, located in upper nasal mucosa
o25 million olfactory cells on each side of mucosa
obipolar neuron cells: their deep processes merge to make plexiform
oplexiform network then recombine to give bundles of nerve that give
olfactory nerve, proper
Nerves come through cribriform (=sieve like) plate: piece of ethmoid bone
oEthmoid bone: thin, complex bone between orbits
oIn middle of cribriform plate: cristae galae: where falx cerebri attaches in
oHoles in cribriform plate: where nerves are transmitted into end of anterior
portion of endocranial fossa
Nerves are attached to olfactory bulbs, which are then joined to olfactory tracts
oBundles of nerve travel through cribriform to olfactory bulbs where they
synapse @ mitral cellsolfactory tracts
oOlfactory tracts connected to telencephalon
oOlfactory bulbs can break lost of smell (anosmia)
oOlfactory cells: degenerate at 1% a year; regenerate
CN II: optic
Special sensory nerve of vision
Nerve begins in retina in back of eyeball
oRetina: developmentally is an outgrowth of brain
oRetina converges at optic disk to become continuous with optic nerve
oOptic nerve is surrounded by meninges because of connexn with retina
oEach optic nerve: million of ganglion cells
Ganglion cells synapse at bipolar cells
Bipolar cells lengthen to form rods and cones
Nerve travels through optic canals: oblique openings
oOptic canals open at junction between anterior middle cranial fossae
Two optic nerves meet to form optic chiasma: in front of pituitary
oNerve fibers from medial half of retina cross in optic chiasma
oLateral fibers stay on the same side
oEffect: carry neurons in related visual field end up in same optic tract
oThe fibers go back to the thalamus or midbrain (lateral geniculate ganglion
or superior colliculi ganglion)
CN III: oculomotor
oComes off of midbrain and goes under the lesser wing of sphenoid
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oGoes through superior orbital fissure: opens into back of orbit
oNerve is lateral to optic nerve
oAssociated with all muscles of the eye: both smooth and striated
oGeneral somatic motor and parasympathetic component
oGeneral somatic motor
oSupply most (5 out of 7) of the muscles around eyeball that move it
oNerve splits immediately after exit
oSuperior division:
Superior rectus: moves eyeball
Levator palpebrae superioris: elevator of upper eyelid
oInferior division
Medial and inferior rectus
Inferior oblique
Three extraocular muscles move eyeball
oParasympathetic: third division of CN III
oSynapse in ciliary ganglion on way to eye
Postganglion parasympathetics carried in short ciliary nerves
oCiliary nerves fibers pierce eyeball and travel to front to supply two
smooth muscles
Pierce sclera and travel between outer and middle coat
Sphincter pupillae: in the iris, controls size of pupil (amount of
Ciliary muscle: surrounds the lens, allows up-close focus
oNasociliary nerve from trigeminal suspends ciliary ganglion but does not synapse
oAll 4 parasymp ganglion suspended by a fiber from trigeminal nerve
CN IV: trochlear
oSmallest CN
oComes off back of back of midbrain
oPasses on side of middle cranial fossa
oExits through superior orbital fissure to travel in medial roof of orbit
oSomatic motor nerve to superior oblique muscle that moves the eye
oSuperior oblique muscle:
oChanges direction of pull within the orbit by passing through a
fibrocartilage loop in superomedial angle of orbit= trochlea
oOrigin: apex of orbit
oInsertion: above eyeball
oMuscles courses along upper medial angle of orbit
CN V: trigeminal
oLargest cranial nerve
oEmerges from pons and goes thru middle cranial fossa
oForms huge semilunar/trigeminal sensory ganglion (medial side of middle cranial
fossa) and divides into 3 pieces
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oPrimary somatic sensory nerve of head; also a motor nerve of first pharyngeal
oLabeling scheme: CN V1, 2, 3
oCN V1 = ophthalmic, entirely sensory
oGoes to superior orbital fissure to join CN III and IV to go to back of orbit
oSupplies cornea, conjunctiva, eyeball, lacrimal gland, forehead, nose,
upper eyelid, frontal and ethmoid sinuses
oEmerges in forehead from frontalis
Lacrimal: small, lateral
provides somatic sensory to lacrimal gland, adjacent eyelid
and conjuncitva (doesn’t control secretions)
Frontal (supraorbital, supratrochlear): both travel to upper medial
corner of eye through foramen
Terminal branches on forehead: sensory
Under levator palpebrae superioris and superior rectus
Four branches
oSuspends ciliary ganglion with sensory root: see
Fibers are considered part of short ciliary
Short ciliary
To back of eyeball, pierce sclera and
travel on eyeball
May contain some sympathetic fibers
oLong ciliary nerves:
Follows same course as short ciliary
Sensory to eye
Primary carrier of sympathetics to ciliary
body, iris
dilate muscles
Side note: sympathetics travel in sympathetic trunk into neck where there are 3 cervical ganglion
superior cerv. Ganglion
obase of skull, above of carotids
owhere sympathetics of head will synapse
ofibers form plexuses around internal and external carotid
ofibers can come up with internal carotid and contribute to CNs
oEthmoidal and nasal: from ethmoidal and
sphenoidal sinuses, nasal cavity and front and tip of
pierces medial wall of orbit
Supplies mucosa
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