L1.3.2.2.1: Cranial Nerves

• CRANIAL NERVES

  ● Located specifically in the inferior part of the brain

  ● 12 pairs – for the head and neck

  ● 1 pair (vagus nerves) – for the thoracic and abdominal cavities

  ● Most cranial nerves are mixed nerves
• CRANIAL NERVES

  ● Mnemonic for the 12 cranial nerves

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  ● Mnemonic for the functions of cranial nerves:

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• 12 Cranial Nerves

  • Olfactory
  • Optic
  • Oculomotor
  • Trochlear
  • Trigeminal
  • Abducens
  • Facial
  • Vestibulocochelear
  • Glossopharyngeal
  • Vagus
  • Accessory
  • Hypoglossal
• OLFACTORY CN I Sensory

  ● Function

  ○ Sense of smell

  ● Test

  ○ Asked to sniff and identity aromatic substances like cloves or vanilla
• OPTIC CN II Sensory

  ● Function

  ○ Sense of sight; vision

  ● Test

  ○ Eye chart

  ○ Testing the point at which the subject first sees an object moving into the visual field

  ○ Eye interior is viewed with an ophthalmoscope
• OCULOMOTOR CN III Motor

  ● Function

  ○ Direct the eyeball, eyelid, and internal eye muscles

  ○ Controls lens shape and pupil size

  ○ Involves: superior, inferior and medial rectus, and inferior oblique

  ● Test

  ○ Pupillary reflex with a penlight where pupils must constrict

  ○ Eye convergence (the ability to follow moving objects)
• TROCHLEAR CN IV Motor

  ● Function

  ○ Supplies motor fibers for one external eye muscle

  ○ Involves: superior oblique

  ○ Moving the eyeball down

  ○ Shifting gaze side to side

  ● Test

  ○ Tested with CN III for the ability to follow moving objects
• TRIGEMINAL CN V Both sensory & motor

  ● Function

  ○ Relays sensation of pain, touch, and temperature

  ○ Mastication (chewing)

  ● Test

  ○ Pain touch and temp: safety pin and hot and cold objects

  ○ Corneal reflex: wisp of cotton

  ○ Mastication: opening mouth against resistance and move jaw from side to side
• ABDUCENS CN VI Motor

  ● Function

  ○ Rolls the eyes laterally

  ○ Involves: lateral rectus muscle

  ● Test

  ○ Tested with CN III for the ability to move EACH eye laterally
• FACIAL CN VII Both sensory & motor

  ● Function

  ○ Facial expression

  ○ Activates lacrimal and salivary gland

  ○ Taste buds of anterior tongue

  ● Test

  ○ Anterior ⅔ of tongue: tested for the ability to taste sweet, salty, sour, and bitter substances

  ○ Asked to close eyes, smile, whistle

  ○ Tearing of eyes: tested with ammonia fumes
• VESTIBULOCOCHLEAR CN VIII Purely sensory

  ● Function

  ○ Vestibular — sense of balance

  ○ Cochlear — sense of hearing ● Test

  ○ Hearing: air and bone conduction using a tuning fork
• GLOSSOPHARYNGEAL CN IX Both sensory & motor

  ● Function

  ○ Swallowing and saliva production

  ○ taste buds of posterior tongue

  ○ Chemical and pressure receptors of the carotid artery

  ● Test

  ○ Gag and swallowing reflexes are checked

  ○ Asked to speak and cough

  ○ Posterior tongue: tested for taste
• ACCESSORY CN XI Motor

  ● Function

  ○ Activate sternocleidomastoid and trapezius muscles

  ○ Shoulder shrugging

  ● Test

  ○ Asked to rotate head and shrug shoulders against resistance
• HYPOGLOSSAL CN XII Motor

  ● Function

  ○ Tongue movements

  ● Test

  ○ Asked to stick out tongue

  ○ Position abnormalities are noted