Cranial Nerves

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Cranial Nerves
General Sensory
Special Sensory
Visceral Sensory
Visceral Motor
Somatic Motor
Branchial 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.

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CN I Olfactory Nerve

• Olfactory Bulb
• Nerve fiber layer axons of primary olfactory
  neurons
• Glomerular layer convergence between axons of
  primary olfactory neurons and dendrites of tufted
  and mitral cells
• External plexiform layer Bodies of tufted cells
• Mitral cell layer single layers of large mitral
  cell bodies
• 5. Granule cell layer contains inhibitory
  interneurons and myelinated axons of secondary
  neurons

• Special Sensory
• Peripheral processes of primary sensory neurons
  in the olfactory epithelium act as sensory
  receptors
• Primary sensory neurons undergo continuous
  replacement throughout life

• Olfactory Epithelium
• Olfactory neurons primary sensory neurons
• 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

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CN II Optic Nerve

• How it works
• Light enters the eye and is transformed into
  electrical signals in the retina
• Optic nerve carries signals to CNS by passing
  through the optic canal and entering the middle
  cranial fossa
• The optic nerves join to form the optic chiasma,
  where some axons go to hypothalamus to influence
  circadian rhythm, and half of he axons cross the
  midline to join uncrossed axons from the other
  eye to form the optic tracts

• Anatomy of Retina
• Macula central point of retina
• Fovea area of retina in the center of the
  macula that provides high-resolution central
  vision it is avascular and has only a single
  layer of photoreceptors and a few cells of Muller
  (glial cells)
• Medial to the fovea is the nasal hemiretina,
  where the optic disc is found just above the
  horizontal meridian
• Optic nerve axons leave the eye and blood
  vessels enter the eye at the optic disc there
  are no photoreceptors here (blind spot)
• Lateral to the fovea is the temporal hemiretina
• Photons transverse all cellular layers of the
  retina before hitting the 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

• Special Sensory
• conveys visual information from the retina

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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 ciliary ganglion,
  and then leave the ganglion as short ciliary
  nerves to reach the ciliary body and constrictor
  pupillae muscle
• these muscles control the size of the pupil and
  shape of the lens
• The parasympathetic axons form the motor limb of
  the light reflex, which constricts the pupils in
  response to bright light (sensory part of reflex
  is controlled by CN II
• These fibers also control the Accommodation
  Reflex, which adapts the visual apparatus for
  near vision

Somatic Motor Innervation of the levator
palpebrae superioris, superior, medial, and
inferior recti, and inferior oblique muscles of
the eye
Visceral Motor Parasympathetic supply to
constrictor pupillae and cilliary muscles
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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

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CN V Trigeminal Nerve
General Sensory Pain and Temperature Simple
Touch All general sensory to face and anterior
scalp Discriminative Touch Proprioception
Vibration Sense

• V1 Ophthalmic Division
• General Sensory nerve with 3 major branches
• Frontal nerve formed by the supraorbital nerve
  (forehead scalp) supratrochlear nerve (
  bridge of nose, medial part of upper eyelid,
  medial forehead)
• Lacrimal nerve sensory information from the
  lateral part of the upper eyelid, conjunctiva,
  and lacrimal gland secretomotor fibers to the
  lacrimal gland from CN VII may travel with the
  lacrimal nerve in its peripheral portion
• Nasociliary nerve formed by the convergence of
  infratrochlear nerve (skin from medial part of
  eyelid and side of nose), external nasal nerve
  (skin from the ala and apex of the nose),
  internal nasal nerve (anterior part of nasal
  septum lateral wall of nasal cavity), anterior
  posterior ethmoidal nerves (ethmoidal air
  sinuses), long short ciliary nerves (bulb of
  eye)
• These divisions join at the superior orbital
  fissure, pass through the cavernous sinus and
  enter the trigeminal ganglion.

• V2 Maxillary Division
• General Sensory nerve with 4 major branches
• Zygomatic nerve consists of zygomaticofacial
  nerve (cheek) zygomaticotemporal nerve (side of
  forehead)
• Infraorbital nerve formed by cutaneous branches
  from upper lip, medial cheek, side of nose
• Superior alveolar nerves (anterior, middle,
  posterior) carry sensory input (pain) from upper
  teeth
• Palatine nerves (greater lesser) originate in
  hard soft palate joined by phayngeal branch
  from nasopharynx nasopalatine nerve from
  posterior nasal cavity
• These join and enter the cranium through the
  foramen rotundum and go to the trigeminal
  ganglion.

Branchial Motor Innervation of the muscles of
mastication

• V3 Mandibular Division
• General Sensory with 4 branches
• Buccal nerve
• Lingual nerve
• Inferior alveolar nerve
• Auriculotemporal nerve

• Branchial Motor with 5 branches
• Medial pterygoid nerve
• Lateral pterygoid nerve
• Masseteric nerve
• Deep temporal nerves
• Mylohyoid nerve

The entire division enters the cranium through
the foramen ovale.
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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

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CN VII Facial Nerve

• General sensory
• found within the nervus intermedius (fascial
  sheath)
• may supplement V3 by providing sensation from
  the wall of the external acoustic meatus
• join branchial motor axons of facial nerve at
  stylomastoid foramen
• Cell bodies are located in geniculate ganglion

• Special Sensory
• carries information from the taste buds on
  lateral border of anterior 2/3 of tongue and the
  hard soft palates
• peripheral processes run with the lingual nerve
  and separate from it to join the chorda tympani
• Cell bodies are located in geniculate ganglion

General Sensory carries sensation from skin of
concha and to possibly supplement V3
Special Sensory Taste sensation from the
anterior two-thirds of the tongue
Visceral Motor parasympathetic stimulation of
the lacrimal, submandibular, sublingual
glandsthe mucous membranes of the nose and hard
and soft palates

• Visceral Motor
• parasympathetic component responsible for
  control of lacrimal, submandibular, sublingual
  glands, and mucous glands of nose, paranasal
  sinuses, hard soft palates
• fibers travel in nrevus intermedius
• divides at geniculate ganglion to form the
  greater pertrosal nerve and part of the chorda
  tympani

Branchial Motor supplies all muscles of facial
expression, and the stapedius, stylohyoid, and
posterior belly of the digastric muscles

• Branchial Motor
• form the efferent component of the corneal
  reflex, light reflex, stapedius reflex, and
  sucking reflex
• Also respond to emotional input

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CN VIII Vestibulocochlear Nerve

• Special sensory
• Vestibular Balance
• Dorsal Ventral Cochlear - Hearing

• Vestibular Component
• Consists of
• utricle saccule expansions of the membranous
  labyrinth containing maculas functions to detect
  the position of the head and movements of the
  head relative to gravity
• 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

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CN IX Glossopharyngeal Nerve

• CN IX leaves cranial fossa through jugular
  foramen with CN X XI
• It contains superior and inferior petrosal
  (glossopharyngeal) ganglia composed of sensory
  components
• CN IX gives rise to 6 terminal branches after it
  passes the jugular foramen tympanic, carotid,
  pharyngeal, tonsilar, lingual, and muscular
  branches

• Parasympathetic Component
• At the inferior ganglion, visceral motor fibers
  leave other modalities as a component of the
  tympanic branch
• They enter the tympanic cavity, passing the
  tympanic plexus and forming the lesser pertrosal
  nerve
• The lesser petrosal nerve descends through the
  foramen ovale and synapses in the otic ganglion
• From here they join the auriculotemporal nerve
  (from V3) to supply the secretomotor fibers to
  the parotid gland

General Sensory posterior 1/3 of tongue, tonsil,
skin of external ear, tympanic membrane pharynx
Visceral Sensory subconscious sensation from
carotid body and carotid sinus
Special Sensory carries taste from the posterior
1/3 of tongue
Visceral Motor parasympathetic stimulation of
the parotid gland, controls blood vessels in
carotid body
Branchial Motor Supplies the styolopharyngeus
muscle
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CN X Vagus Nerve

• Branches of CN X
• Jugular Fossa
• Meningeal general sensory
• Auricular general sensory
• Neck
• Pharyngeal general visceral sensory,
  branchial visceral motor
• Superior laryngeal general visceral sensory,
  branchial visceral motor
• Internal laryngeal general visceral sensory,
  visceral motor
• External laryngeal branchial motor
• Recurrent laryngeal (right) general visceral
  sensory, branchial visceral motor
• Cardiac visceral sensory motor
• Thorax
• Cardiac Visceral sensory motor
• Recurrent laryngeal (left) general visceral
  sensory, branchial visceral motor
• Pulmonary visceral sensory motor
• Esophageal visceral sensory motor
• Abdomen
• Gastrointestinal Visceral sensory motor

General Sensory from posterior meninges, concha,
skin at back of ear, external tympanic membrane,
pharynx larynx
Visceral Motor parasympathetic stimulation to
smooth muscle glands of the pharynx, larynx
thoracic abdominal viscera cardiac muscle
Visceral Sensory from larynx, trachea,
esophagus, thoracic abdominal viscera,
stretch receptors chemoreceptors
Branchial Motor superior, middle, inferior
constrictors levator palati, salpingopharyngeus,
palatopharyngeus, palatoglossus
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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 matter of C1-C6
  (because its not in the brain it could show up
  on the exam)
• The nerve enters the cranium through the foramen
  magnum, traveling in the subarachnoid space, and
  exits through the jugular foramen to end on its
  target muscles

• Branchial Motor
• supplies sternocleidomastoid trapezius muscles

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CN XII Hypoglossal Nerve

• Somatic motor
• supplies 3 of 4 extrinsic muscles of tongue all
  intrinsic muscles of tongue

• The only extrinsic tongue muscle that is not
  supplied by the hypoglossal nerve is the
  palatoglossus muscle (supplied by CNX)
• 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