HEAD/NECK : Cranial Nerves

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HEAD/NECK Cranial Nerves

• Special Sense Nerves
• I,II,VIII
• Somatic Motor Nerves
• EyeIII,IV,VI
• Tongue--XII
• Rest of body nerves
• IX,X,XI
• Face and jaws
• VII, V

Human Anatomy, Frolich, Head/Neck IV Cranial
Nerves
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Nerve targets in head

• SENSORY
• Special General
• Smell skin
• Vision teeth
• Hearing eye
• tongue
• oral cavity
• nasal cavity
• middle ear
• throat
• meninges

• MOTOR
• Muscles Glands
• eyes salivary
• extrinsic sweat
• intrinsic lacrimal
• jaws mucous
• facial expression
• larynx
• tongue
• throat
• ear

Human Anatomy, Frolich, Head/Neck IV Cranial
Nerves
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Base of the skullcranial nerves out

• Ethmoid (olfactory)
• I. Olfactory
• Sphenoid (optic)
• II. Optic
• III. Oculomotor
• IV. Trochlear
• VI. Abducens
• Temporal (otic)
• VII. Acoustic/Auditory/
• Vestibulocochlear
• Face/Jaws
• V. Trigeminal
• VII. Facial
• Throat (rest of body)
• IX Glossopharyngeal
• X. Vagus
• XI. Spinal Accessory
• XII. Hypoglosal

Human Anatomy, Frolich, Head/Neck IV Cranial
Nerves
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Special Sense Nerves
Human Anatomy, Frolich, Head/Neck IV Cranial
Nerves
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Human Anatomy, Frolich, Head/Neck IV Cranial
Nerves
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Somatic Motor Nerves(eye muscles and tongue)
Human Anatomy, Frolich, Head/Neck IV Cranial
Nerves
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Human Anatomy, Frolich, Head/Neck IV Cranial
Nerves
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Human Anatomy, Frolich, Head/Neck IV Cranial
Nerves
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Human Anatomy, Frolich, Head/Neck IV Cranial
Nerves
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Rest of body nerves(all exit from jugular
foramen)
Human Anatomy, Frolich, Head/Neck IV Cranial
Nerves
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Human Anatomy, Frolich, Head/Neck IV Cranial
Nerves
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Human Anatomy, Frolich, Head/Neck IV Cranial
Nerves
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Cranial Nerves

• Twelve pairs
• 2 attach to forebrain (Telen- Diencephalon)
• 10 attach to brainstem (Mes-, Met- and
  Myelencephalon)
• Names relate to appearance or function
• Classification ?

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Olfactory Nerve ( CN or N I)

• 1º function?
• Origin?
• Destination? _____________(By way of cribiform
  plate of ethmoid)
• Only CN directly attached to Cerebrum

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Visual System

• Eye
• Accessory structures
• Eyebrows, eyelids, eyelashes, tear glands
• Protect eyes from sunlight and damaging particles
  
• Optic nerve (II)
• Tracts
• Pathways
• Eyes respond to light and initiate afferent
  action potentials

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Optic Nerve (N II)

• 1º fu?
• ori?
• dest? - by way of optic foramen of sphenoid to
  Diencephalon (optic chiasma) and to occipital
  lobe

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Oculomotor (N III)

• C Motor
• O Mesencephalon
• D Somatic motor to superior, inferior, medial
  recti and inferior oblique visceral motor to
  intrinsic eye muscles
• by way of superior orbital fissure

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Trochlear (N IV)

• C Motor
• O Mesencephalon
• D superior oblique
• by way of superior orbital fissure

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Trigeminal (N V)

• C Mixed
• three major branches
• 1. ophthalmic (sensory)
• 2. Maxillary (sensory)
• 3. Mandibular (mixed)
• O face / nuclei of pons
• D sensory nuclei in pons / muscles of
  mastication

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V Trigeminal (3 nerves in 1!)

• V1. Ophthalmic
• Exits with eye muscle group (superior orbital
  fissure, through orbit to superior orbital
  notch/foramina)
• Sensory to forehead, nasal cavity
• V2. Maxillary
• Exits foramen rotundum through wall of maxillary
  sinus to inferior orbital foramina)
• Sensory to cheek, upper lip, teeth, nasal cavity
• V3. Mandibular
• Exits foramen ovale to mandibular foramen to
  mental foramen
• Motor to jaw muscles--Masseter, temporalis,
  pterygoids, digastric
• Sensory to chin
• Sensory to tongue

Human Anatomy, Frolich, Head/Neck IV Cranial
Nerves
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Human Anatomy, Frolich, Head/Neck IV Cranial
Nerves
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Abducens(CN VI)
C Motor O Pons D Runs lateral rectus eye
muscle
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VII Facial Nerve(exits cranial cavity with
VIII--internal auditory meatus)

• Facial muscles (five branches fan out over face
  from stylomastoid foramen)
• Temporal
• Zygomatic
• Buccal
• Mandibular
• Cervical
• chorda tympani (crosses interior ear drum to
  join V3 )
• Taste to anterior 2/3 of tongue
• Submandibular, sublingual salivary glands
• Lacrimal glands

Human Anatomy, Frolich, Head/Neck IV Cranial
Nerves
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Facial (N VII)

• C Mixed
• O sensory from taste receptors of anterior 2/3
  of tongue / motor from pons
• D Sensory to sensory nuclei of pons / motor
  muscles of facial expression, visceral motor to
  tear gland.

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Human Anatomy, Frolich, Head/Neck IV Cranial
Nerves
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Vestibulocochlear (N VIII)
C O ? D
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Glossopharyngeal (CN IX)
C mixed O sensory from posterior 1/3 of tongue
/ motor from medulla oblongata D medulla /
muscles for swallowing, parotid gland
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Vagus (N X)

• C Mixed
• O Sensation from pharyngeal area and outer ear /
  motor from medulla
• D Sensory to medulla / visceral motor to
  thoracic and abdominal cavities and their organs.
  Major motor pathway for ANS

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Accessory (N XI) and

• C Motor
• O Motor nuclei of medulla and spinal cord
• D Swallowing, trapezius scm muscles
• Hypoglossal (N XII)
• C Motor
• O Motor nuclei of medulla
• D Tongue musculature

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Mnemonic
Out On Our Table Top Are Fruits, Very Green
Vegetables And Hamburgers
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Extrinsic Eye Muscles
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Anatomy of the Eye

• Three coats or tunics
• Fibrous Consists of sclera and cornea
• Vascular Consists of choroid, ciliary body, iris
• Nervous Consists of retina

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Anatomy of the Eye

• Fibrous tunic Outer
• Sclera White outer layer, maintains shape,
  protects internal structures, provides muscle
  attachment point, continuous with cornea
• Cornea Avascular, transparent, allows light to
  enter eye and bends and refracts light
• Vascular tunic Middle
• Iris Controls light entering pupil smooth
  muscle
• Ciliary muscles Control lens shape smooth muscle

• Retina Inner
• Contains neurons sensitive to light
• Macula lutea or fovea centralis Area of greatest
  visual acuity
• Optic disc Blind spot
• Compartments
• Anterior Aqueous humor
• Posterior Vitreous humor
• helps maintain ocular pressure
• keeps eye inflated
• largely responsible for shape of eye
• Lens
• Held by suspensory ligaments attached to ciliary
  muscles
• Transparent, biconvex

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Functions of the Complete Eye

• Eye functions like a camera
• Iris allows light into eye
• Lens, cornea, humors focus light onto retina
• Light striking retina is converted into action
  potentials relayed to brain

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The Retina

• Provides black backdrop for increasing visual
  acuity
• Sensory retina and pigmented retina
• Photoreceptors
• Rods Noncolor vision
• Rhodopsin reduction Light adaptation
• Rhodopsin production Dark adaptation
• Cones Color vision

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Sensory Receptor Cells
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Rods and Cones

• Photoreceptors are depolarized in the dark,
  continuously releasing neurotransmitter.
• When hyperpolarized by light--gtdecrease amount of
  neurotransmitter.
• Rods- activated below starlight. Scotopic
  vision, no color, poor acuity.
• Cones- activated with brighter light. Photopic
  vision. Color vision.

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Rods and Cones

• Most of what we think of as seeing is mediated by
  cones.
• Individual loses cone vision, legally blind.
• Individual loses rod vision, experience
  difficulties at low levels of illumination (night
  blindness).
• Cones are only receptors in fovea.

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Other visual pathways

• Ganglion cells--gt pretectum. Between thalamus
  and midbrain. Coordinates the pupillary reflex.
• Suprachiasmatic nucleus of the hypothalamus.
  Involved in day/night cycle and biological
  rhythms.
• Superior colliculus in midbrain. Coordinates
  head and eye movements.

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