CRANIAL NERVES

INTRODUCTION

–  12 pairs of cranial nerves

–  Table 15.6 summarizes all nerves
-- Table 15.7 lists each nerve in detail

CN I: OLFACTORY:
– sensory axons only

–  function:  smell (olfaction)

– olfactory nerves synapse in olfactory bulb

–  olfactory bulbs connect to olfactory tracts

–  test for nerve damage: test smell

CN II: OPTIC:
–  sensory axons only

–  function: vision

–  optic chiasm

–  optic tracts

–  test for nerve damage:

CN III: OCULOMOTOR

- somatic motor and parasympathetic motor axons

–  functions:

1. somatic motor:  supplies 4 eye muscles (superior rectus, inferior rectus, medial rectus, inferior oblique) and a muscle in the upper eyelid (levator palpebrae superioris)

2.  parasympathetic motor: supplies iris, will help constrict pupil

–  test for nerve damage:

1.  does pupil constrict?

2.  does the upper eyelid droop?

3.  Does person have diplopia?

CN IV: TROCHLEAR:
–  somatic motor axons

–  function:  supplies superior oblique
–  test for nerve damage: diplopia?

CN V: TRIGEMINAL:
– somatic motor and sensory axons

–  functions:

1.  motor:  muscles of mastication
2.  sensory:  anterior part of scalp, entire face, nasal cavity, oral cavity, teeth

–  test for nerve damage:

1.

2.

CN VI: ABDUCENS:
–  somatic motor axons
–  function: supplies lateral rectus
–  test for nerve damage:

SO - NOW YOU CAN REVIEW THE EYE MUSCLES MEMORY MATRIX

CN VII: FACIAL:
– somatic motor, special sensory, and parasympathetic motor axons

–  functions:

1.  somatic motor: muscles of facial expression
2.  sensory: TASTE to anterior 2/3 of tongue

3.  parasympathetic motor: increases secretion of lacrimal glands, most salivary glands

–  test for nerve damage:

CN VIII: VESTIBULOCOCHLEAR:
–  contains sensory axons only!

–  functions: hearing and equilibrium

–  test for nerve damage:

1.  test for hearing loss/deafness
2.  is person experiencing vertigo, lack of balance, dizziness, nausea/vomiting?

CN IX: GLOSSOPHARYNGEAL:
–  contains somatic motor, general & special sensory, and parasympathetic motor axons!

–  functions:

1.  somatic motor:  supplies one pharynx (throat) muscle
2.  general sensory: touch and TASTE sensation of post 1/3 of tongue
3.  parasympathetic motor:  increases secretion to parotid gland

–  test for nerve damage:

CN X: VAGUS:

–  contains primarily somatic motor and parasympathetic motor axons

–  functions:

1.  somatic motor: supplies most pharynx (swallowing) muscles and larynx (voice box) muscles

parasympathetic motor: supply muscle in the heart, lungs, most abdominal organs

–  test for nerve damage:

1.  does person have difficulty swallowing?
2.  does person have a hoarse voice, permanent loss of voice

CN XI: ACCESSORY:
–  contains somatic motor axons

–  functions:  innervates trapezius and sternocleidomastoid         

 
–  test for nerve damage:

CN XII: HYPOGLOSSAL:
–  somatic motor axons
–  functions:  supplies intrinsic tongue muscles and most extrinsic tongue muscles

–  test for nerve damage:

Before you get a cavity filled in your tooth, you HOPE that the dentist will anesthetize (numb) a branch of this nerve:

a.   CN IV (trochlear)

b.   CN V (trigeminal)

c.   CN VII (facial)

d.   CN IX (glossopharyngeal)

e.   CN X (vagus)