Anatomy & Physiology: The Cranial Nerves Flashcards

I. Olfactory


Function: Purely sensory- Carries impulses for sense
of smell

Testing: Person is asked to sniff and identify
aromatic substances, such as oil or cloves and vanilla

II. Optic


Function: Purely sensory- Carries impulses for vision

Testing: Vision and visual fields are determined with
eye chart and by testing the point at which the person first sees the
object (finger) moving into the visual field. Eye interior viewed with
ophthalmoscope to detect swelling of optic disc (point which optic
nerve leaves the eye) and to observe blood vessels

III. Oculomotor


Function: Mixed- motor fibers to inferior oblique and
superior,inferior, and medial rectus muscles, which direct eyeball; to
levator palpebrae muscles of eyelids; to iris and smooth muscle
controlling lens shape and pupil size

Testing: Pupils are examined for size, shape, and
equality. Pupillary reflex is tested with penlight (pupils should
constrict when illuminated). Convergence for near vision is tested, as
is subject's ability to follow objects up, down, side to side, and
diagonally with eyes

IV. Trochlear


Function: Mixed- provides motor fibers to superior
oblique muscle (an extrinsic eye muscle)

Testing: Tested in common with cranial nerve III

V. Trigeninal


Function: Mixed-conducts sensory impulses from skin
of face and anterior scalp, from mucosae of mouth and nose; also
contains motor fibers that activate the chewing muscles

Testing: Sensations of pain, touch, and temperature
are tested with safety pin and hot and cold objects. Corneal reflex
tested with wisp of cotton. Motor branch assessed by asking person to
clench his teeth, open mouth against resistance, and move jaw side to side

VI. Abducens


Function: Carries motor fibers to lateral rectus
muscle of eye

Testing: tested in common with cranial nerve III.

VII. Facial


Function: Mixed- supplies motor fibers to muscles of
facial expression and to lacrimal and salivary glands; carries sensory
fibers from taste receptors of anterior tongue

Testing: Anterior two-thirds of tongue is tested for
ability to taste sweet (sugar), salty, sour (vinegar), and bitter
(quinine) substances. Symmetry of face is checked. Subject is asked to
close eyes, smile, whistle, and so on. Tearing is assessed with
ammonia fumes

VIII. Vestibulocochlear


Function: Purely sensory- transmits impulses for
senses of equilibrium and hearing

Testing: Hearing is checked by air and bone
conduction using tuning fork

IX. Glossopharyngeal


Function: Mixed- motor fibers serve pharyngeal
muscles and salivary glands; sensory fibers carry impulses from
pharynx, posterior tongue (taste buds), and pressure receptors of
carotid artery

Testing: Gag and swallowing reflexes are
checked.subject is asked to speak and cough. Posterior third of tongue
may be tested for taste.

X. Vagus


Function: Mixed- motor fibers to pharynx and larynx
and sensory fibers from same structures; a very large portion is
composed of parasympathetic motor fibers, which supply heart and
smooth muscles of abdominal visceral organs; transmits sensory
impulses from viscera

Testing: As for cranial nerve IX (IX and X are tested
in common, since they both serve muscles of the throat and mouth.)

XI. Accessory


Function: Mixed- provides motor fibers to
sternocleidomastoid and trapezius muscles

Testing: Sternocleidomastoid and trapezius muscles
are checked for strength by asking person to rotate head and elevate
shoulders against resistance

XII. Hypoglossal


Function: mixed- motor fibers serve muscles of tongue
and sensory fibers carry impulses from tongue.

Testing: Person is asked to protrude and retract
tongue. Any deviations in position are noted

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