Chapter 8 The Sensory System
Chapter Objectives
Upon completion of the chapter the participant will be able to:
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2.
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6.
7.
Describe the structures involved with hearing.
Describe the structures involved with seeing.
Discuss the physiology of being able to see.
Discuss the physiology of being able to hear.
Analyze, define, spell and pronounce the medical terms common to the ear.
Analyze, define, spell and pronounce the medical terms common to the eye.
Successfully complete the review exercises at the end of the chapter.
The Eye
Our eyes are the receptor organs for the sense of sight and provide the window that lets
in the light of the outside world. Light waves are transformed by the eye into nerve
impulses that are sent to the occipital lobe of the brain. Here the waves are processed
and we experience vision.
It is the job of the eye to let light in, focus it, transform it into an impulse and send the
impulse to the brain. Light enters the eye through the pupil (pupil/o, core/o) and then
passes through the lens (phac/o, phak/o) found behind the pupil. The lens has the
ability to adjust its shape in order to adjust to objects that are close at hand and those
that are at a distance. As many people age their lens may become cloudy which will
affect their ability to see. This condition is referred to as cataracts. The light from the
lens then goes to the back of the eyeball where it strikes the retina (retin/o). It is the
retina that transforms the image into a nerve impulse. The impulses travel along the
optic nerve to the brain.
The eye consists of two parts: the inner eye and the outer eye.
Inner Eye
 Consists of three layers: outer, middle and inner
 Outer layer consists of the cornea (corne/o, kerat/o) and the sclera (scler/o).
The cornea is the transparent anterior portion of the sclera that allows light into
the eye and allows for focusing of the light on the back of the eye. The sclera is
known as the “white of the eye” which maintains the shape of the eye and
protects the delicate inner structures.
 Middle layer is the vascular layer and is referred to as the uvea (uve/o) and
consists of the choroid (choroid/o) the ciliary body (cycl/o) and iris (ir/o, irido/,
irit/o, ir/i). The choroid is the inner lining of the sclera and has the blood vessels
that nourish the eye. The ciliary body consists of muscles that change the shape
of the lens so you are able to see things at various distances. This process is
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referred to as accommodation. The ciliary body is responsible to produce a
liquid that bathes the anterior surface of the eye.
The iris is the circular colored part of the eye. The center of the iris is a circular
opening called the pupil (pupill/o, core/o) that regulates the amount of light that
can get into the eye. In bright light the pupil will constrict and in darkness it will
dilates.
 Inner layer consists of the retina. This is nerve tissue made up of rods and
cones. They transform light into nerve impulses.
Ciliary Body
Retina
Conjunctiva
Iris
Blood Vessels
Pupil
Path of Light
Anterior Chamber
Cornea
Lens
Optic Nerve
Vitreous Humor
Choroid
Sclera
Choroid
Outer Eye
The outer eye consists of the orbital cavity, ocular muscles, the eyelids (palpebr/o,
blephar/o) the conjunctival membrane (conjunctiv/o) and the lacrimal apparatus
(lacrim/o, dacry/o). The orbital cavity acts as a protective device for the eyeball. The
six muscles allow the eye to move in all directions. The eyelid acts as a protection from
dust and dirt entering the eye and the membrane lubricates as well as protects the
eyeball. The lacrimal glands produce tears that continuously bathe the eye. The tears
drain into the back of the nasal cavity that explains why your nose runs when you cry.
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Lacrimal Gland
Pupil
Sclera
Conjunctiva
Nasolacrimal Duct
Iris
Word Parts for the Eye
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aque/o
blephar/o, palpebr/o
chrom/o
chori/o, choroid/o
conjunctiv/o
core/o, pupill/o
corne/o, kerat/o
cycl/o
dacry/o, lacrim/o
dipl/o
irid/o, ir/o, ir/i, irit/o
mi/o
mydri/o
ocul/o, ophthalm/o, opt/o, optic/o, opt/i
papill/o
phac/o, phak/o
phot/o
presby/o
retin/o
scler/o
ton/o
uve/o
vitre/o
-chalasis
-opia, -opsia
-ptosis
-pexy
-tropia, -tropion
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water
eyelid
color
choroids
conjunctiva
pupil
cornea
ciliary body
tear/lacrimal duct, tears
double
iris
contraction, less, smaller
wide, dilation
eye, vision, sight
optic disc
lens
light
old age
retina
sclera
tension
uvea
glasslike, glassy, gel like
relaxation
vision, visual condition
drooping, sagging
put in place
turning
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esoexoextraintra-
inward
outward
on the outside
on the inside
Term Analysis and Definition (The Eye)
Word Part
Term
aque/o
aqueous
humor
aque = water
-ous = pertaining to
humor = body fluid
Pertaining to the watery fluid
found in the anterior chamber
of the eye.
blephar/o,
palpebr/o
blepharoptosis
blephar = eyelid
-ptosis = drooping
Drooping of the eyelid
palpebral
palpebr = eyelid
-al = pertaining to
Pertaining to the eyelid
chorioretinitis
chori = choroid
-itis = inflammation
retin = retina
Inflammation of the choroid
and retina
chori/o,
choroid/o
Term Analysis
choroiditis
Definition
Inflammation of the choroid
conjunctiv/o
conjunctivitis
conjunctiv =
conjunctiva
-itis = inflammation
Inflammation of the
conjunctivia
(Also known as “pinkeye”)
core/o
pupill/o
coreometer
core = pupil
-meter = instrument
to measure
Instrument used to measure
the size of the pupil
pupillary
pupil l= pupil
-ary = pertaining to
Pertaining to the pupil
corneal
corne = cornea
-al = pertaining to
Pertaining to the cornea
kerat = cornea
-conus = cone
shaped
Abnormal, cone-shaped
protrusion of the cornea
corne/o,
kerat/o
keratoconus
cycl/o
cycloplegia
cycl = ciliary body
-plegia = paralysis
Paralysis of the ciliary body
dacry/o
lacrim/o
dacryostenosis
dacry = tear duct
-stenosis =
narrowing
Narrowing of the tear duct
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Word Part
Term
nasolacrimal
irid/o, ir/o
Term Analysis
nas = nose
lacrim = tear
-al = pertaining to
Definition
Pertaining to the nose and tear
(lacrimal) apparatus
iritis
irid = iris
-itis = inflammation
Inflammation of the iris
iridectomy
-ectomy = excision
Excision of the iris
miosis
mi = contraction,
less, smaller
-osis = abnormal
condition
Abnormal contraction of the
pupil
miotic
-tic = pertaining to
Pertaining to a drug that
constricts the pupil
mydri/o
mydriatic
mydri = wide,
dilation
-tic = pertaining to
Pertaining to a drug that dilates
the pupil
ocul/o,
opt/o,
optic/o,
opt/i,
ophthalm/
binocular
bi = two
ocul = eye
-ar = pertaining to
Pertaining to both eyes
extraocular
extra = outside
-ar = pertaining to
Pertaining to the outside of the
eye
intraocular
intra = inside, within
Pertaining to within the eye
exophthalmia
ex = outward
ophthalm = eye
-ia = condition
Condition where there is
outward protrusion of the
eyeball
ophthalmologist
-logist = specialist
Specialist in the study and
diagnosis of diseases of the
eye
ophthalmology
-logy = study of
Study of diseases of the eye
optic
opt = vision, sight
-ic = pertaining to
Pertaining to vision or sight
optician
-ician = specialist,
expert
One who specializes in
prescribing glasses for
improving sight
mi/o
opt/o
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Word Part
Term
Term Analysis
Definition
optometrist
-metrist = specialist
in the measurement
of
Specialist in the testing of
visual function and in diagnosis
and nonsurgical treatment of
eye conditions.
papill/o
papilledema
papill = optic disc
edema = accumulation of fluid
Accumulation of fluid in the
optic disc
phac/o,
phak/o
aphakia
a = no, lack of
phak = lens
ia = condition
Absence of a lens
phacomalacia
phac = lens
-malacia = softening
phot/o
photophobia
phot = light
-phobia = fear
Fear of or intolerance to light
retin/o
retinopathy
retin = retina
-pathy = disease
Disease of the retina
scler/o
sclerectomy
scler = sclera
-ectomy = excision,
surgical removal
Surgical excision of the sclera
ton/o
tonometry
ton = tension
-metry = process of
measuring
Measurement of the intraocular
pressure
uve/o
uveitis
uve = uvea
-itis = inflammation
Inflammation of the uvea of the
eye
vitre/o
vitreous humor
vitre = gel-like
-ous = pertaining to
Pertaining to the gel-like
substance in the posterior
cavity of the eye
-chalasis
blepharochalasis
blephar = eyelid
-chalasis =
relaxation
Relaxation of the eyelid
-tropia
esotropia
eso = inward
-tropia = turning
Turning inward of the eyeball.
Also referred to as “cross-eyes”
exotropia
exo = outward
Turning outward of the eyeball
amblyopia
ambly = dull, dim
-opia = vision
Dimness of vision
Softening of a lens
-opia,
-opsia
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Word Part
Term
-tropion
Term Analysis
Definition
diplopia
di = double
Double vision
presbyopia
presby = old age
Impaired vision due to aging
hyperopia
hyper = above,
excessive
Farsightedness ( the light rays
go beyond the retina)
myopia
my = to shut
(Light rays focus in front of the
retina) nearsightedness
ectropion
ec = out
-tropion = turning
Outward turning of the eyelid
entropion
en = inward
Inward turning of the eyelid
Vocabulary Words:
Accommodation
The process whereby the eyes make adjustments for seeing
objects at various distances
Cararact
An opacity of the crystalline lens or its capsule; most often occurs
in adults past middle age.
Conjunctivitis
Inflammation of the conjunctiva caused by allergy, trauma,
chemical injury, bacterial, viral or infection. The type ‘pinkeye’ is
infectious and contagious
Enucleation
A process of removal of the eyeball from the orbit
Glaucoma
A disease characterized by a increased intraocular pressure which
results in atrophy of the optic nerve and blindness
Nystagmus
An involuntary, constant, rhythmic movement of the eyeball
Snellen Chart
A chart for testing visual acuity
Strabismus
a squint
Abbreviations:
OP
intraocular pressure
OD
oculus dexter (right eye)
OS
oculus sinister (left eye)
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PERLA
pupil equal and reactive to light and accommodation
REM
rapid eye movement
The Ear
The ear is the sensory organ that allows us to hear. It consists of the external ear,
middle ear and inner ear. The ear is responsible for hearing and as well plays an
important role in our balance. The word roots audi/o, and audit/o mean hearing.
The hearing process consists of detecting and transmitting sound waves for
interpretation. Detecting involves receiving the sound stimulus and then it is transmitted
though a nerve called the auditory nerve to the temporal lobe of the brain where it is
interpreted.
Malleus
Incus
Semicircular
Canals
Auricle
External ear
Canal
Cochlea
Eustachian
tube
Tympanic
Membrane
Stapes
External Ear
 Composed of the auricle, external auditory meatus, and eardrum or the tympanic
membrane.
 Auricle (pinn/i, aur/o, aur/i) is also referred to as the pinna and is the external
part of the ear that is attached to the head. It catches the sound waves and
channels them into the external ear canal.
 The canal that moves into the ear from the pinna is referred to as the external
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auditory canal. It is responsible to channel the sound waves toward the
eardrum.
Middle Ear
 The middle ear begins with the tympanic membrane (tympan/o, myring/o) or
the eardrum as it is commonly referred to. When the sound waves reach the
membrane they cause it to vibrate and the vibration causes the waves to travel
into the middle ear.
 In the middle ear are three small bones malleus, incus, and stapes. These
bones are often referred to as the hammer, anvil and stirrup because of their
shape. These bones begin vibrating when the sound waves hit them.
 The air pressure that is found on either side of the eardrum must be kept equal.
To do this there is a eustachian tube that connects the middle ear to the throat.
If for some reason this tube becomes blocked a sense of pressure will build up in
the middle ear and your ability to hear is affected.
 The middle ear is surrounded by mastoid cells (mastoid/o) that are hollow
spaces in the mastoid bone located directly behind the ear.
Inner Ear
 If you think of a sponge you have a good idea of what the inner ear is like; a
twisting series of canals and larger spaces. These canals and spaces are
encased in bone that is referred to as the bony labyrinth (labyrinth/o).
 This is the part of the ear that has the receptors needed for both hearing and
your balance.
 The bony labyrinth consists of the vestibule, semicircular canals and the cochlea.
The vestibule and semicircular canals are important in maintaining your sense of
balance. The cochlea is responsible for hearing.
 Sound is transmitted into the cochlea through the oval window. In the cochlea is
the organ of Corti that contains fine hair cells that move because of the sound
waves. This movement stimulates the nerve cells that create the impulse that is
transmitted to the brain.
Word Parts for the Ear
Roots
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acoust/o, acous/o
audi/o, audit/o
aur/o, aur/i,ot/o
cochle/o
labyrinth/o
mastoid/o
myring/o, tympan/o
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hearing, related to hearing
hearing, ear
ear, hearing
cochlea (snail, spiral)
labyrinth, inner ear
mastoid process
ear drum, tympanic membrane
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myc/o
pinn/i
salping/o
staped/o
tinnit/o
fungus
external ear
eustachian tube
stapes
ringing, buzzing
Suffixes
 -algia, -dynia
 -cusis
pain
hearing
Prefixes
 bi mon-
two
one
Term Analysis and Definition (The Ear)
Word Part
Term
audio/o,
audit/o
audiogram
audio = hearing
-gram = record
Record of hearing
audiometry
-merty = process of
measuring
Measurement of hearing
auditory
audit = hearing
-ory = pertaining to
Pertaining to hearing
aural
aur = ear
-al = pertaining to
Pertaining to the ear
otalgia
ot = ear
-algia = pain
Earache
otitis media
-itis = inflammation
media = middle
Inflammation in the middle ear
otorrhea
-rrhea = discharge
Discharge from the ear
otoscope
-scope = instrument
to visually examine
Instrument to visually examine
the ear
otosclerosis
-sclerosis
= hardening
Hardening of the bones of the
ear
aur/o , ot/o,
aur/i
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Term Analysis
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Definition
Word Part
Term
Term Analysis
Definition
otorrhagia
-rrhagia = bleeding
Bleeding from the ear
cochle/o
cochlear
cochle - cochlea
-ar = pertaining to
Pertaining to the cochlea
labryinth/o
labyrinthitis
labyrinth = inner ear
-itis = inflammation
Inflammation of the inner ear
mastoid/o
mastoidectomy
mastoid = mastoid
bone
-ectomy = surgical
removal
Surgical removal of the
mastoid bone
myring/o,
tympan/o
myringotomy
myring = ear drum
-tomy = surgical
incision
Surgical incision into the ear
drum
tympanocentesis
-centesis = puncture
to remove fluid
Puncture in the ear drum for
removal of fluid
salping/o
salpingoscope
salping = eustachian
tube (ear)
scope = instrument
used to visually
examine
Instrument used to visually
examine the eustachian tube
staped/o,
stapedi/o
stapedectomy
Surgical excision of the stapes
tinnit/o
tinnitus
staped = stapes
-ectomy = surgical
excision
tinnit = ringing
-us = thing
-cusis
presbycusis
presby = old age
-cusis = hearing
Diminished hearing from old
age
Vocabulary Words:
Cerumen
earwax
Equilibrium
a state of balance
Vertigo
a feeling of dizziness
Abbreviations:
AD
auris dexter (right ear)
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Ringing in something. Term
used to refer to “ringing in
the ears”
AS
auris sinistra (left ear)
ENT ear, nose and throat
EENT eyes, ears, nose throat
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