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CRANIAL NERVES Cranial

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CRANIAL NERVES Cranial Powered By Docstoc
					                      Cranial Nerves
                                          General
                                          Sensory
                           Special                        Visceral
                           Sensory                        Sensory




                           Visceral
                                                        Somatic
                           Motor                        Motor
                                         Branchia
                                         l Motor




 Note: This powerpoint is color coded the same as our cranial nerve book. As in the book,
sensory means the same as afferent, and motor is means the same as efferent. Whenever
you see visceral motor think PARASYMPATHETICS! This powerpoint is not comprehensive,
                        it is only a study aid and is highly simplified.
                               CN I: Olfactory Nerve
Olfactory Bulb:
1.   Nerve fiber layer:
     axons of primary
     olfactory neurons
2.   Glomerular layer:
     convergence
     between axons of
                                       Special Sensory
     primary olfactory            •   Peripheral processes of
     neurons and                      primary sensory neurons in
     dendrites of tufted
     and mitral cells
                                      the olfactory epithelium act
                                      as sensory receptors
3.   External plexiform
     layer: Bodies of tufted      •   Primary sensory neurons
     cells                            undergo continuous
4.   Mitral cell layer:               replacement throughout life
     single layers of large
     mitral cell bodies
5.   Granule cell layer:
     contains inhibitory                                             Olfactory Epithelium:
     interneurons and
     myelinated axons of                                             1.   Olfactory neurons: primary
     secondary neurons                                                    sensory neurons
                                                                     2.   Sustentacular cells:
                                                                          supporting cells
                                                                          intermingled with the
                                                                          sensory cells; similar to glia
                                                                     3.   Basal Cells: source of new
                                                                          receptor cells; only place in
                                                                          CNS continuously
                                                                          regenerating throughout life
                             CN II: Optic Nerve
How it works:
• Light enters the eye and                              Anatomy of Retina:
is transformed into
electrical signals in the                               • Macula: central point of retina
retina                                                  • Fovea: area of retina in the center
                                                        of the macula that provides high-
•Optic nerve carries                                    resolution central vision; it is
signals to CNS by passing                               avascular and has only a single layer
through the optic canal                                 of photoreceptors and a few cells of
and entering the middle                                 Muller (glial cells)
cranial fossa                                           • Medial to the fovea is the nasal
                                                        hemiretina, where the optic disc is
• The optic nerves join to                              found just above the horizontal
form the optic chiasma,                                 meridian
where some axons go to                                  • Optic nerve axons leave the eye
hypothalamus to influence                               and blood vessels enter the eye at
circadian rhythm, and half                              the optic disc; there are no
of he axons cross the                                   photoreceptors here (blind spot)
midline to join uncrossed        Special Sensory        • Lateral to the fovea is the temporal
axons from the other eye
to form the optic tracts
                                 • conveys visual       hemiretina
                                                        • Photons transverse all cellular
                                 information from the   layers of the retina before hitting the
                                 retina                 photoreceptors
                                                        •The photoreceptors (rods and
                                                        cones) then transduce light energy
                                                        into electrical energy and pass the
                                                        info forward to the bipolar cells,
                                                        which pass the signal further to
                                                        ganglion cells
                                                        • Ganglion cell axons converge
                                                        toward the optic disc, pass through
                                                        the lamina cribiformis of the sclera
                                                        and leave the eye as the optic nerve
                  CN III: Oculomotor Nerve
Parasympathetic
Component:
• axons are located on the
surface of CN III, so when the
nerve is compressed they are the
first to lose their function
• these axons terminate in the         Somatic Motor:
ciliary ganglion, and then leave       Innervation of the levator
the ganglion as short ciliary          palpebrae superioris,
nerves to reach the ciliary body       superior, medial, and inferior
and constrictor pupillae muscle
                                       recti, and inferior oblique
• these muscles control the size       muscles of the eye
of the pupil and shape of the lens
• The parasympathetic axons
form the motor limb of the light
reflex, which constricts the pupils   Visceral Motor:
in response to bright light
                                      Parasympathetic supply to
(sensory part of reflex is
controlled by CN II                   constrictor pupillae and cilliary
                                      muscles
• These fibers also control the
Accommodation Reflex, which
adapts the visual apparatus for
near vision
       CN IV: Trochlear Nerve

Somatic Motor
Innervation of the
   superior oblique
   muscle of the eye



                       •Smallest of the cranial nerves
                       •Enters the orbit through the superior fissure, runs
                       above the levator palpebrae superioris muscle to reach
                       the superior oblique muscle
                           CN V: Trigeminal Nerve
V1: Ophthalmic Division                                                                                             V2: Maxillary Division
General Sensory nerve with 3 major                   General Sensory:                                               General Sensory nerve with 4 major
     branches:                                       Pain and Temperature; Simple                                        branches
1.     Frontal nerve: formed by the                  Touch; All general sensory to
                                                     face and anterior scalp;                                       1.    Zygomatic nerve: consists of
       supraorbital nerve (forehead &
                                                                                                                          zygomaticofacial nerve (cheek) &
       scalp) & supratrochlear nerve (               Discriminative Touch;
                                                                                                                          zygomaticotemporal nerve (side of
       bridge of nose, medial part of                Proprioception; Vibration Sense                                      forehead)
       upper eyelid, & medial forehead)
                                                                                                                    2.    Infraorbital nerve: formed by
2.     Lacrimal nerve: sensory
                                                                                                                          cutaneous branches from upper lip,
       information from the lateral part of
                                                                                                                          medial cheek, & side of nose
       the upper eyelid, conjunctiva, and
       lacrimal gland; secretomotor fibers           Branchial Motor:                                               3.    Superior alveolar nerves (anterior,
       to the lacrimal gland from CN VII                                                                                  middle, posterior): carry sensory input
                                                     Innervation of the muscles of
       may travel with the lacrimal nerve                                                                                 (pain) from upper teeth
       in its peripheral portion                     mastication
                                                                                                                    4.    Palatine nerves (greater & lesser):
3.     Nasociliary nerve: formed by the                                                                                   originate in hard & soft palate; joined
       convergence of infratrochlear                                                                                      by phayngeal branch from
       nerve (skin from medial part of                                                                                    nasopharynx & nasopalatine nerve
       eyelid and side of nose), external                                                                                 from posterior nasal cavity
       nasal nerve (skin from the ala and
                                                                                                                    These join and enter the cranium through
       apex of the nose), internal nasal
                                                                                                                          the foramen rotundum and go to the
       nerve (anterior part of nasal
                                                                                                                          trigeminal ganglion.
       septum & lateral wall of nasal
       cavity), anterior & posterior
       ethmoidal nerves (ethmoidal air
                                               V3: Mandibular Division
                                                                                           Branchial Motor with 5 branches
       sinuses), & long & short ciliary        General Sensory with 4 branches
       nerves (bulb of eye)                                                                1.     Medial pterygoid nerve
                                               1.    Buccal nerve
These divisions join at the superior orbital                                               2.     Lateral pterygoid nerve
                                               2.    Lingual nerve
      fissure, pass through the                                                            3.     Masseteric nerve
      cavernous sinus and enter the            3.    Inferior alveolar nerve
      trigeminal ganglion.                                                                 4.     Deep temporal nerves
                                               4.    Auriculotemporal nerve
                                                                                           5.     Mylohyoid nerve


                                                The entire division enters the cranium through the foramen ovale.
    CN VI: Abducens Nerve
                             • Only function is to move the eye laterally away
                             from midline
                             •The nerve enters the cavernous sinus,
                             between the internal carotid artery and CN III,
                             IV, V1 & V2
                             • It leaves the sinus and enters the orbit at the
                             medial end of the superior orbital fissure




Somatic Motor:
Innervation of the lateral
     rectus muscle of the
     eye
                               CN VII: Facial Nerve
General sensory:                                                                                             Special Sensory:
• found within the nervus                                                                                    • carries information from the
intermedius (fascial sheath)
                                                                                                             taste buds on lateral border of
• may supplement V3 by                                                                                       anterior 2/3 of tongue and the
providing sensation from the wall                                                                            hard & soft palates
of the external acoustic meatus
                                                                                                             • peripheral processes run with
• join branchial motor axons of                          General Sensory:                                    the lingual nerve and separate
facial nerve at stylomastoid                             carries sensation                                   from it to join the chorda
foramen                                                  from skin of concha                                 tympani
                                                         and to possibly
•Cell bodies are located in                              supplement V3                                       •Cell bodies are located in
geniculate ganglion                                                                                          geniculate ganglion
                                                                                         Special Sensory:
                                                                                         Taste sensation
                                                                                         from the anterior
                                    Visceral Motor:                                      two-thirds of the
                                    parasympathetic                                      tongue
 Visceral Motor:                    stimulation of the
                                    lacrimal,
 • parasympathetic                  submandibular, &
 component responsible              sublingual
 for control of lacrimal,           glands;the mucous
                                                                Branchial Motor:                                     Branchial Motor:
 submandibular,                     membranes of the
                                                                supplies all muscles
 sublingual glands, and             nose and hard and
                                                                of facial expression,                                • form the efferent
 mucous glands of nose,             soft palates
                                                                and the stapedius,                                   component of the corneal
 paranasal sinuses, &
                                                                stylohyoid, and                                      reflex, light reflex,
 hard & soft palates
                                                                posterior belly of the                               stapedius reflex, and
 • fibers travel in nrevus                                      digastric muscles                                    sucking reflex
 intermedius
                                                                                                                     •Also respond to
 • divides at geniculate                                                                                             emotional input
 ganglion to form the
 greater pertrosal nerve
 and part of the chorda
 tympani
       CN VIII: Vestibulocochlear Nerve
                                                                              Vestibular Component:
                                                                              Consists of:
          Special sensory:                                                    • utricle & saccule: expansions of the membranous labyrinth
          •      Vestibular – Balance                                         containing maculas; functions to detect the position of the
                                                                              head and movements of the head relative to gravity
          •      Dorsal & Ventral
                 Cochlear - Hearing                                           • semicircular canal: three tubes of membranous labyrinth
                                                                              extending from the utricle; oriented at right angles to each
                                                                              other and containing ampullas and endolymph
                                                                              • vestibular nerve: primary sensory neurons whose cell bodies
                                                                              are form the vestibular ganglion; the central processes form
                                                                              the vestibular component of CN VIII




Cochlear Component:
• contains three small bones (malleus, incus, & stapes) that carry sound
waves from the tympanic membrane to the oval window and amplify the
force per unit area of sound
• the cochlea communicates with the middle ear cavity via 2 openings in
the bone: oval window (fenestra vestibuli) and round window (fenestra
cochlea), which are covered by the secondary tympanic membrane
• the cochlear duct divides the cochlea into the scala vestibuli, scala
tympani, & scala media (cochlea duct itself)
• stereocilia (hair cells) convert mechanical energy into electrical energy
   CN IX: Glossopharyngeal Nerve
• CN IX leaves cranial fossa
through jugular foramen with
CN X & XI                                                                                              Parasympathetic Component:
• It contains superior and                                                                             • At the inferior ganglion, visceral
inferior petrosal                          General                                                     motor fibers leave other modalities
                                                                          Visceral
(glossopharyngeal) ganglia                 Sensory:                                                    as a component of the tympanic
                                                                          Sensory:
composed of sensory                        posterior 1/3 of               subconscious                 branch
                                           tongue, tonsil,                sensation from
components                                                                                             • They enter the tympanic cavity,
                                           skin of external               carotid body
• CN IX gives rise to 6 terminal           ear, tympanic                                               passing the tympanic plexus and
                                                                          and carotid
branches after it passes the               membrane &                                                  forming the lesser pertrosal nerve
                                                                          sinus
jugular foramen: tympanic,                 pharynx
                                                                                                       • The lesser petrosal nerve
carotid, pharyngeal, tonsilar,                                                                         descends through the foramen
lingual, and muscular branches                                                      Special
                                                                                                       ovale and synapses in the otic
                                   Visceral Motor:                                  Sensory: carries
                                                                                    taste from the
                                                                                                       ganglion
                                   parasympathetic
                                   stimulation of                                   posterior 1/3 of   • From here they join the
                                   the parotid                                      tongue             auriculotemporal nerve (from V3) to
                                   gland, &                                                            supply the secretomotor fibers to
                                   controls blood             Branchial Motor:
                                                                                                       the parotid gland
                                   vessels in                 Supplies the
                                   carotid body               styolopharyngeu
                                                              s muscle
                                     CN X: Vagus Nerve
Branches of CN X:
Jugular Fossa
1.     Meningeal – general sensory                                            General Sensory:
                                                                              from posterior
2.     Auricular – general sensory                                            meninges,
Neck                                                                          concha, skin at
                                                                              back of ear,
1.     Pharyngeal – general & visceral sensory,                               external tympanic
       branchial & visceral motor                                             membrane, &
2.     Superior laryngeal – general & visceral           Visceral Motor:
                                                                              pharynx & larynx
       sensory, branchial & visceral motor                                                            Visceral Sensory:
                                                         parasympathetic
                                                                                                      from larynx,
3.     Internal laryngeal – general & visceral           stimulation to
                                                                                                      trachea,
                                                         smooth muscle &
       sensory, visceral motor                                                                        esophagus, &
                                                         glands of the
                                                                                                      thoracic &
4.     External laryngeal – branchial motor              pharynx, larynx;
                                                                                                      abdominal
                                                         thoracic &
5.     Recurrent laryngeal (right) – general &                                                        viscera, stretch
                                                         abdominal
                                                                                                      receptors &
       visceral sensory, branchial & visceral motor      viscera & cardiac
                                                                             Branchial Motor:         chemoreceptors
                                                         muscle
6.     Cardiac – visceral sensory & motor                                    superior, middle,
                                                                             inferior constrictors;
Thorax                                                                       levator palati,
1.     Cardiac – Visceral sensory & motor                                    salpingopharyngeu
                                                                             s,
2.     Recurrent laryngeal (left) – general & visceral                       palatopharyngeus,
       sensory, branchial & visceral motor                                   palatoglossus

3.     Pulmonary – visceral sensory & motor
4.     Esophageal – visceral sensory & motor
Abdomen
1.     Gastrointestinal – Visceral sensory & motor
       CN XI: Accessory Nerve
                            • The accessory nerve is not technically a cranial nerve!
                            • The accessory nucleus is located in the lateral part of the anterior grey
Branchial Motor:            matter of C1-C6 (because it’s not in the brain it could show up on the
supplies                    exam)
    sternocleidomastoid &   • The nerve enters the cranium through the foramen magnum, traveling
    trapezius muscles       in the subarachnoid space, and exits through the jugular foramen to end
                            on its target muscles
  CN XII: Hypoglossal Nerve
                              •The only extrinsic tongue muscle that is
Somatic motor:
                              not supplied by the hypoglossal nerve is
supplies 3 of 4 extrinsic     the palatoglossus muscle (supplied by
    muscles of tongue & all
                              CNX)
    intrinsic muscles of
    tongue                    •Extrinsic muscles act to protrude,
                              elevate, and retract the tongue
                              •Intrinsic muscles change the shape of the
                              tongue
                              •The tongue has 2 important functions:
                              eating & swallowing, and performing
                              movements of speech
                              •The neural projections of the hypoglossal
                              are bilateral except the cortical neurons
                              that innervate genioglossus muscles
                              •Because of this the genioglossus is used
                              in clinical testing of CN XII (see book for
                              info)
                              •Because the hypoglossal nuclei are
                              located very close together, nuclear
                              lesions usually affect both nuclei which
                              results in a bilateral loss of innervation to
                              the tongue
nnervation to
                               the tongue

				
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