590
UNIT 3
Regulation and Integration of the Body
When emergency personnel arrived
on the scene of the bus crash, they
found Brian Rhen, 42, sitting on the
side of the road holding his head in
his hands. He complained of a severe headache and nausea, and
was evaluated and treated for a concussion. Several days later,
Mr. Rhen began to experience recurring episodes of vertigo and
was referred to a neurologist. (Vertigo is a sensation of motion or
movement while the person is stationary, and can be accompanied
by nausea and vomiting.)
Mr. Rhen was diagnosed with
benign paroxysmal positional
vertigo
(BPPV). With this condition, which can be caused by head
trauma, vertigo can be provoked by specific changes in head
position. Mr. Rhen reported that his vertigo usually occurred
when rolling over in bed, or when turning his head from side to
side while sitting up, and that these movements provoked the
sensation of a spinning room, which led to nausea. The neurologist
confirmed the diagnosis of BPPV by using a test called the Dix-
Hallpike maneuver. During this test, the neurologist looks for
nystagmus (involuntary, jerking eye movements) as he makes
specific rotational changes to Mr. Rhen’s head position.
1.
The ear is divided into three major areas (compartments). What
are these three areas, and which of these areas is involved in
Mr. Rhen’s BPPV?
2.
What are the three main sources of sensory input that the body
uses in order to control balance and equilibrium?
3.
Name the two functional divisions of the vestibular apparatus.
Identify the sensory receptor associated with each division, and
state which aspect of equilibrium each receptor senses.
4.
BPPV can be caused by otoliths that have been dislodged
from the otolithic membrane of the maculae. Based on Mr.
Rhen’s symptoms and the head movements that provoke
these symptoms, what part of the vestibular apparatus are the
displaced otoliths now affecting?
5.
Explain why nystagmus is associated with the Dix-Hallpike
maneuver.
(Answers in Appendix H)
Case Study
Special Senses
Related Clinical Terms
Ageusia
(ah-gu
9
ze-ah) Loss or impairment of the taste sense.
Age-related macular degeneration (ARMD)
Progressive
deterioration of the macula lutea that destroys central vision;
the main cause of vision loss in those over age 65. Buildup of
pigments in the macula impairs functioning of the pigmented
epithelium. Continued accumulation of pigment leads to the
“dry” form of ARMD, in which many pigment cells and macular
photoreceptors die. Te dry form is largely untreatable, although
a specific cocktail of vitamins and zinc slows its progression.
Less common is the “wet” form in which new blood vessels from
the choroid grow into the retina. Blood and fluids leak from
these vessels, scarring and detaching the retina. Te cause of wet
ARMD is unknown, but several treatment options can slow its
progression—laser treatments that destroy some of the invading
vessels and drugs that prevent blood vessel growth. Clinical trials
using RNA interference to inhibit vascular growth are underway.
Blepharitis
(blef
0
ah-ri
9
tis;
blephar
5
eyelash;
itis
5
inflammation)
Inflammation of the margins of the eyelids.
Enucleation
(e-nu
0
kle-a
9
shun) Surgical removal of an eyeball.
Exophthalmos
(ek
0
sof-thal
9
mos;
ex
5
out;
ophthalmo
5
the
eye) Anteriorly bulging eyeballs. Seen in some cases of
hyperthyroidism.
Labyrinthitis
Inflammation of the labyrinth.
Ophthalmology
(of
0
thal-mol
9
o-je) Te science that studies the eye
and eye diseases. An ophthalmologist is a medical doctor who
specializes in treating eye disorders.
Optometrist
A licensed nonphysician who measures vision and
prescribes corrective lenses.
Otalgia
(o-tal
9
je-ah;
algia
5
pain) Earache.
Otitis externa
Inflammation and infection of the external acoustic
meatus, caused by bacteria or fungi that enter the canal
from outside, especially when the canal is moist (e.g., aFer
swimming).
Otoacoustic emissions
Sounds generated by the movement of outer
hair cells in the cochlea. Stimulated otoacoustic emissions are an
inexpensive way to screen newborns for hearing defects.
Papilledema
(pap
0
il-ĕ-de
9
mah;
papill
5
nipple;
edema
5
swelling)
Protrusion of the optic disc into the eyeball, which can
be observed by ophthalmoscopic examination; caused by
conditions that increase intracranial pressure.
Scotoma
(sko-to
9
mah;
scoto
5
darkness) A blind spot other than
the normal (optic disc) blind spot. Has many causes, including
stroke or a brain tumor pressing on fibers of the visual pathway.
Trachoma
(trah-ko
9
mah;
trach
5
rough) A highly contagious
bacterial (chlamydial) infection of the conjunctiva and cornea.
Common worldwide, it blinds millions of people in poor
countries of Africa and Asia. ±reated with eye ointments
containing antibiotic drugs.
Weber’s test
Hearing test during which a sounding tuning fork is held
to the forehead. In those with normal hearing, the tone is heard
equally in both ears. Te tone will be heard best in the “good”
ear if sensorineural deafness is present, and in the “bad” ear if
conduction deafness is present.
AT T H E C L I N I C
15
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