Case 2

• Cranial nerves are composed of twelve pairs of nerves that emanate from the brain and exit/enter the cranium through openings in the skull
• Motor components of cranial nerves are derived from cells in the brain and control muscle, glandular tissue, or specialized muscle outside the brain
• Sensory components of cranial nerves originate from collections of cells located outside the brain, called sensory ganglia
• Sensory ganglia of cranial nerves send branches that divide into two branches: one that enters the brain and one connected to a sensory organ
• Exceptions to the rule of sensory components are noted when discussing the special senses of smell and vision
• Motor components of cranial nerves transmit nerve impulses from the brain to target tissue outside of the brain
• Sensory components of cranial nerves transmit nerve impulses from sensory organs to the brain
• Cranial nerves include: Olfactory, Optic, Oculomotor, Trochlear, Trigeminal, Abducent, Facial, Vestibulocochlear, Glossopharyngeal, Vagus, Accessory, Hypoglossal
• Sensory cranial nerves contain only afferent (sensory) fibers, motor cranial nerves contain only efferent (motor) fibers, mixed nerves contain both sensory and motor fibers
• Nerves with parasympathetic fibers include: Oculomotor, Facial, Glossopharyngeal, Vagus
• General Innervation categories include GSE (motor to somatic voluntary skeletal muscles), GSA (sensory to skin, joints, muscle, and tendon receptor endings), GVE (motor to smooth muscles and glands), GVA (sensory to gut, blood vessels, and internal organs)
• Special Innervation categories include SSA (special senses of vision, auditory sensation, and vestibular apparatus), SVA (chemical senses of taste and smell), SVE (motor to voluntary skeletal muscles)
• Cranial nerves in order: Olfactory (Smell), Optic (Vision), Oculomotor (Motor to eye muscles, Parasympathetic to eye muscles), Trochlear (Motor to superior oblique muscle), Trigeminal (Branchial Motor, General Sensory), Abducent (Motor to lateral rectus muscle), Facial (Branchial Motor, Visceral Motor, General Sensory, Special Sensory), Vestibulocochlear (Hearing and Balance), Glossopharyngeal (Branchial Motor, Visceral Motor, Visceral Sensory, General Sensory, Special Sensory), Vagus (Branchial Motor, Visceral Motor, Visceral Sensory, Special Sensory), Accessory (Branchial Motor), Hypoglossal
• Sensory cranial nerves include: Olfactory (Smell), Optic (Vision), Vestibulocochlear (Hearing and Balance)
• Motor cranial nerves include: Oculomotor, Trochlear, Abducent, Accessory, Hypoglossal
• Mixed cranial nerves include: Trigeminal, Facial, Glossopharyngeal, Vagus
• Olfactory Nerve: Responsible for the sense of smell, passes through the cribriform plate to the olfactory bulb, can lead to hyperosmia, hypoosmia, anosmia, or dysosmia when affected
• Optic Nerve: Responsible for vision, passes through the optic canal to the lateral geniculate body, visual field defects can occur when affected
• Oculomotor Nerve: Supplies muscles of the eye and controls the pupil and ciliary muscle, includes parasympathetic fibers, can lead to oculomotor nerve palsy
• Trochlear Nerve: Supplies the superior oblique muscle, arises from the trochlear nucleus in the midbrain
• Trigeminal Nerve: Branchial motor and general sensory functions, innervates muscles of mastication and provides sensory input for the head/neck, sinuses, and meninges
• Trigeminal nerve (CN V) supplies the superior oblique muscles
• Sensory aspect of the trigeminal nerve originates from the cells of the trigeminal ganglion
• For pain and temperature sensations from the face:

  • Neuron 1: Cells of trigeminal ganglion
  • Neuron 2: Cells of spinal nucleus of the trigeminal in the medulla
  • Neuron 3: Cells of PMVNT
• Ophthalmic nerve (V1, sensory) leaves the skull through the superior orbital fissure to enter the orbital cavity

  • Branches:
  • Frontal nerve
  • Supratrochlear nerve
  • Supraorbital nerve
  • Lacrimal nerve
  • Nasociliary nerve
  • Distribution:
  • Sensation from cerebral dura mater
  • Visual organ
  • Mucosa of nose
  • Skin above the eye and back of nose
• Maxillary nerve (V2, sensory) leaves the skull through foramen rotundum

  • Important branches:
  • Infraorbital nerve
  • Zygomatic nerve
  • Posterior superior alveolar nerve
  • Pterygopalatine nerve
  • Distribution:
  • Sensation from cerebral dura mater
  • Maxillary teeth
  • Mucosa of nose and mouth
  • Skin between eye and mouth
• Mandibular nerve (V3, mixed) leaves the skull through the foramen ovale to enter the infratemporal fossa

  • Important branches:
  • Auriculotemporal nerve
  • Buccal nerve
  • Lingual nerve
  • Inferior alveolar nerve
  • Nerve of masticatory muscles
  • Distribution:
  • Sensation from cerebral dura mater
  • Teeth and gum of lower jaw
  • Mucosa of floor of mouth
  • Anterior 2/3 of tongue
  • Skin of auricular and temporal regions and below the mouth
  • Motor to masticatory muscles, mylohyoid, and anterior belly of digastric
• Abducens nerve (CN VI) supplies the lateral rectus muscle
• Brodmann's Areas:

  • Area 3, 1 & 2: Primary Somatosensory Cortex
  • Area 4: Primary Motor Cortex
  • Area 6: Premotor cortex and Supplementary Motor Cortex (Secondary Motor Cortex)
  • Area 8: Frontal eye fields
  • Area 10: Anterior prefrontal cortex
  • Area 17: Primary visual cortex
  • Area 18: Secondary visual cortex
  • Area 19: Associative visual cortex
  • Area 22: Superior temporal gyrus, containing Wernicke's area
  • Area 36: Ectorhinal area, part of the perirhinal cortex
  • Area 39: Angular gyrus
  • Area 40: Supramarginal gyrus, part of Wernicke's area
  • Area 43: Primary gustatory cortex
• • Area 45: Broca's area
• Cranial nerves 7-12: origin, course, distribution, and function
• Facial Nerve:

  • Course and branches
• Vestibulocochlear (auditory = statoacoustic) Nerve:

  • Course
• Glossopharyngeal Nerve:

  • Deep origin and branches of the 9th cranial nerve
  • Extra cranial part of the 9th nerve
  • General and taste sensations from the tongue
• Vagus Nerve:

  • Deep origin and branches of the vagus nerve
  • Extra cranial part of the vagus nerve
• Accessory Nerve
• Hypoglossal Nerve:

  • All muscles of the tongue are supplied by the hypoglossal nerve except palatoglossus supplied by the cranial part of the accessory nerve through the vagus