Anatomy and Physiology
Chapter 8: Special Senses
The Eye and Vision
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When provided with a model or diagram, identify the
accessory eye structures and list the functions of each.
Name the eye tunics and indicate the major function of each.
Explain how rod and cone function differ.
Describe image formation on the retina.
Trace the pathway of light through the eye to the retina.
Discuss the importance of an ophthalmoscopic examination.
Define the following terms: accommodation,
astigmatism, blind spot, cataract, emmetropia, glaucoma,
hyperopia, myopia, and refraction.
Trace the visual pathway to the optic cortex.
Discuss the importance of the pupillary and convergence reflexes.
The Ear: Hearing and Balance
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Identify the structures of the external, middle, and
internal ear, and list the functions of each.
Explain the function of the organ of Corti in hearing.
Define sensorineural and conductive deafness
and list possible causes of each.
Explain how one is able to localize the source of a sound.
Describe how the equilibrium organs help maintain balance.
Chemical Senses: Taste and Smell
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
Describe the location, structure, and function
of the olfactory and taste receptors.
Name the four basic taste sensations and list
factors that modify the sense of taste.
Developmental Aspects of the Special Senses
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Describe changes that occur in the special sense organs with age.
2009-2010 P. Holman
Anatomy and Physiology
Chapter 8: Special Senses
The Eye and Vision

When provided with a model or diagram, identify the
accessory eye structures and list the functions of each.
http://webvision.med.utah.edu/anatomy.html
http://wps.aw.com/bc_marieb_ehap_8/25/6527/1671070.cw/index.html
see figure 8.1 pg 253 of your text for external/accessory structures: eyelids,
eyelashes, meibomian glands, ciliary glands, conjunctiva, lacrimal glands, lacrimal
canals, lacrimal sac, nasolacrimal duct extrinsic eye muscles.
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Name the eye tunics and indicate the major function of each.
Tunics or coats are (in order, exterior to interior): sclera (thick white connective
tissue, called fibrous tunic = white of eye) of which the most anterior part is clear,
forming the cornea; choroids (middle coat; blood rich, dark with pigments that
prevent light scattering, forms the ciliary body attaching the lens and the iris,
surrounds the pupil), retina (inner tunic; contains rods and cones the photoreceptors)
No rods or cones at the optic disc (blind spot) – do the test on pg 257 of your book,
under figure 8.5.
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Explain how rod and cone function differ.
2009-2010 P. Holman
Anatomy and Physiology
Rods are more concentrated at the periphery of the retina and allow us to see gray
tones in dim light. They are responsible for our peripheral vision. Vitamin A is
important for rod maintenance.
Cones allow us to see color in bright light, are most dense near the center of the
retina. The fovea centralis, lateral to each blind spot only contains cones. This is the
area of greatest visual acuity. There are 3 types of cones, sensitive to blue light, to
green light and a third ranging from green and red (these are called red cones).
Am I colorblind? On-line test:
http://colorvisiontesting.com/online%20test.htm#demonstration%20card

Describe image formation on the retina.
Light bends as it passes through the cornea, the aqueous humor, the lens and the
vitreous humor. It bends more if the lens is thicker (more convex), less if the lens is
thinner (less convex). Normal vision is set for distance vision. The light passes
through the structures, focusing on the focal point at the back of the retina. The
image is real and upside down.
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Trace the pathway of light through the eye to the retina.
Light passes through the cornea, the aqueous humor, the lens and the vitreous
humor before focusing on the retina.
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Discuss the importance of an ophthalmoscopic examination. This instrument
illuminates the interior of the eye, showing the retina, optic disc and internal
blood vessels. This allows one to detect diabetes, arteriosclerosis and
degeneration of the optic nerve and retina.
http://archopht.ama-assn.org/cgi/content/full/119/6/819?ck=nck
http://archopht.ama-assn.org/cgi/content/full/119/6/819/FIGECS00089F1?ck=nck
https://www.blueshieldca.com/hw/articles/hw_article.jsp?articleId=HWHW5223&fro
mCategoryId=8&_requestid=1252309
http://www.cis.rit.edu/pelz/lab/papers/Hammer_Ferguson_Magill_White%20Image%
20stabilization%20for%20scanning%20laser%20ophthalmoscopy.pdf
http://www.netterimages.com/image/15618.htm
http://www.nlm.nih.gov/medlineplus/ency/article/003881.htm
http://www.stlukeseye.com/Conditions/DiabeticRetinopathy.asp
2009-2010 P. Holman
Anatomy and Physiology
http://www.mdguidelines.com/atherosclerosis-and-arteriosclerosis
http://www.merck.com/mmhe/sec20/ch225/ch225c.html
http://www.i-care.net/faq-amd.htm
http://webvision.med.utah.edu/index.html
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Define the following terms:
accommodation,
ac·com·mo·da·tion
Pronunciation: \ə-ˌkäm-ə-ˈdā-shən\
Function: noun
: an adaptation or adjustment especially of a bodily part (as an organ): as a : the
automatic adjustment of the eye for seeing at different distances effected chiefly by
changes in the convexity of the crystalline lens b : the range over which such
adjustment is possible
astigmatism,
astig·ma·tism
Pronunciation: \ə-ˈstig-mə-ˌtiz-əm\
Function: noun
1 : a defect of an optical system (as a lens) causing rays from a point to fail to meet in
a focal point resulting in a blurred and imperfect image
2 : a defect of vision due to astigmatism of the refractive system of the eye and
especially to corneal irregularity—compare EMMETROPIA, MYOPIA
blind spot,
blind spot
Function: noun
: the small circular area in the retina where the optic nerve enters the eye that is
devoid of rods and cones and is insensitive to light—called also optic disk
[blind spot illustration]
cataract,
cat·a·ract
Pronunciation: \ˈkat-ə-ˌrakt\
Function: noun
: a clouding of the lens of the eye or its surrounding transparent membrane that
obstructs the passage of light
emmetropia
em·me·tro·pia
Pronunciation: \ˌem-ə-ˈtrō-pē-ə\
Function: noun
: the normal refractive condition of the eye in which with accommodation relaxed
2009-2010 P. Holman
Anatomy and Physiology
parallel rays of light are all brought accurately to a focus upon the retina—compare
ASTIGMATISM, MYOPIA
—em·me·trop·ic \-ˈträp-ik, -ˈtrōp-\ adjective
glaucoma
glau·co·ma
Pronunciation: \glau̇-ˈkō-mə, glȯ-\
Function: noun
: a disease of the eye marked by increased pressure within the eyeball that can result
in damage to the optic disk and gradual loss of vision
Physician-reviewed articles on glaucoma on Healthline.
1. Glaucoma (4 images)
Glaucoma refers to a group of disorders that lead to dama...
Visually explore glaucoma HealthMaps on
Healthline:
1. Glaucoma
2. Hydrophthalmos
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hyperopia
hy·per·opia
Pronunciation: \ˌhī-pə-ˈrō-pē-ə\
Function: noun
: a condition in which visual images come to a focus behind the retina of the eye and
vision is better for distant than for near objects—called also farsightedness,
hypermetropia
—hy·per·opic \-ˈrō-pik, -ˈräp-ik\ adjective
Physician-reviewed articles on hyperopia on Healthline.
1. Hyperopia (1 image)
Hyperopia, also known as hypermetropia or farsightedness,...
Visually explore hyperopia HealthMaps on Healthline:
1. Farsightedness
2. Eye Disorders
myopia
my·o·pia
Pronunciation: \mī-ˈō-pē-ə\
Function: noun
: a condition in which the visual images come to a focus in front of the retina of the
eye because of defects in the refractive media of the eye or of abnormal length of the
eyeball resulting especially in defective vision of distant objects—called also
nearsightedness; compare ASTIGMATISM 2, EMMETROPIA
Physician-reviewed articles on myopia on Healthline.
1. Nearsightedness (3 images)
Nearsightedness is when the eyes focus incorrectly, makin...
2009-2010 P. Holman
Anatomy and Physiology
Visually explore myopia HealthMaps on Healthline:
1. Nearsightedness
2. Eye Disorders
refraction
re·frac·tion
Pronunciation: \ri-ˈfrak-shən\
Function: noun
1 : the deflection from a straight path undergone by a light ray or a wave of energy in
passing obliquely from one medium (as air) into another (as water or glass) in which
its velocity is different
2 a : the refractive power of the eye b : the act or technique of determining ocular
refraction and identifying abnormalities as a basis for the prescription of corrective
lenses
Source:
http://www.merriam-webster.com/
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Trace the visual pathway to the optic cortex.
http://thalamus.wustl.edu/course/basvis.html
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Discuss the importance of the pupillary and convergence reflexes.
Convergence reflexes cause both eyes to move medially when viewing something
really close. This allows both eyes to aim at the object. The pupils also constrict
when our eyes converge. This is called the accommodation pupillary reflex.
The photopupillary reflex is when both pupils constrict when exposed to bright light.
This prevents excess light from damaging the rods and cones (photoreceptors).
The Ear: Hearing and Balance
(http://mypages.iit.edu/~smile/bi8910.ht
ml)
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Identify the structures of the external,
middle, and
2009-2010 P. Holman
Anatomy and Physiology
internal ear, and list the functions of
each.
The external ear consists of the pinna
or auricle (ear) and the external
auditory canal. The auricle is
designed to direct and collect sound
waves into the canal of most animals,
but does not do this in humans. The
canal directs sound into the skull. It
contains ceruminous glands that
secrete cerumen or earwax. It ends at
the tympanic membrane or eardrum.
http://webschoolsolutions.com/patts/s
ystems/ear.htm
http://hyperphysics.phyastr.gsu.edu/HBASE/sound/earsens.h
tml
http://www.physicsclassroom.com/cl
ass/sound/U11l2d.cfm
2009-2010 P. Holman
Anatomy and Physiology
The middle ear, or tympanic cavity, is
filled with air within the temporal
bone. It starts at the tympanic
membrane and ends at the bony wall
containing the oval window and the
round window. It also has the
auditory tube, running from the
middle ear to the throat. The middle
ear works when the pressure inside
and outside the ear is equal. The tube
helps with this. Otitis media or
inflammation of the middle ear is
common in children, because their
auditory canal is more horizontal.
The ossicles (hammer, anvil and
stirrup or malleus, incus and stapes)
span this area, transmitting
movement from the tympanic
membrane to the inner ear. The
stirrup connects with the oval
window.
2009-2010 P. Holman
Anatomy and Physiology
http://www.medicinenet.com/otitis_m
edia/article.htm#
http://www.vestibular.org/vestibulardisorders/specificdisorders/labyrinthitisvestneuritis.php
The inner ear contains bony
chambers or osseous labyrinth in
shapes known as the cochlea the
vestibule and the semicircular canals.
It is filled with perilymph. The
membranous labyrinth is filled with
thicker endolymph. This is where the
sounds are transmitted into neural
signals sent to the auditory part of the
brain.
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Explain the function of the organ of
Corti in hearing.
2009-2010 P. Holman
Anatomy and Physiology
Housed in the cochlea, the organ of
Corti contains hair cells or hearing
receptors. The fluids move the hairs
as they move in the tectorial
membrane covering them. High
pitches disturb receptors near the oval
window, low pitches stimulate hairs
farther away. The hairs transit
impulses along the cochlear nerve,
part of nerve VIII, the
vestibulocochlear nerve). The sound
reaches the ears at different times,
creating a stereo effect. The
receptors can become “immune” to a
repetitive sound and stop signaling
the brain. Hearing is the last sense to
shut off and the first to turn on when
we go to sleep and awaken.
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Define sensorineural and conductive
deafness and list possible causes of
each.
2009-2010 P. Holman
Anatomy and Physiology
Conduction deafness results from
interruption of the sound vibrations to
the inner ear fluids. It could be wax
buildup, fusion of ossicles, ruptured
eardrum, or otitis media. One may
still be able to hear, with bone
conduction apparatus (hearing aid).
Sensorineural deafness happens with
damage to receptor cells in the organ
of Corti, to the cochlear nerve, or to
neurons of the auditory cortex. This
can result from really loud sounds.
Equilibrium problems result in
nausea, dizziness and balance
problems because the vestibular
apparatus impulses differ from visual
cues.
Meniere’s syndrome results in
progressive deafness, causing nausea
and vertigo. It is caused by
2009-2010 P. Holman
Anatomy and Physiology
arteriosclerosis, degeneration of
cranial nerve VIII or pressure in the
inner ear. Anti-motion-sickness
drugs help.
Am I deaf?
http://www.phys.unsw.edu.au/jw/hear
ing.html
http://www.freehearingtest.com/test.s
html
http://www.rnid.org.uk/howwehelp/h
earing_check/take_online_hearing_ch
eck/?from=/hearing-check-homeright-bott-panel/
http://longislandaudiology.com/onlin
e_test.php
http://www.freehearingtest.ca/index_f
lash.html
2009-2010 P. Holman
Anatomy and Physiology
http://www.handtronix.com/webdata/
flash/onlinescreener.html
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Explain how one is able to localize
the source of a sound.
http://en.wikipedia.org/wiki/Sound_loc
alization
http://www.cs.cmu.edu/~rms/Binaural
Web/papers/SternWangBrownChapter.
pdf
http://www.plosbiology.org/article/info
:doi/10.1371/journal.pbio.0030027
in bats:
http://www.springerlink.com/content/c
a965k6tk0ldf8cq/
http://www.sciencedaily.com/releases/
1999/06/990617072054.htm
2009-2010 P. Holman
Anatomy and Physiology
in rats:
http://www.ratbehavior.org/rathearing.
htm
http://www.physorg.com/news1191008
77.html
prpt:
http://psy2.ucsd.edu/~dmacleod/159/pr
esentations05/MichaelSound%20Local
ization%20of%20Humans.ppt

Describe how the equilibrium organs
help maintain balance.
There are membrane sacs inside the
vestibule of the inner ear. They
contain hair cells, hair tufts, fluid and
otoliths, tiny stones made of calcium
salts. Gravity affects the movement
of the thick fluid. When one tilts
their head, the fluid moves the
2009-2010 P. Holman
Anatomy and Physiology
otoliths, which brush against the hair
tufts signaling the nerve fibers blow
the hair cells. This lets the brain
know its position, with respect to
gravity.
Receptors in the semicircular canals
(oriented x, y z) respond to angular
movements. The receptor, crista
amullaris, is a tuft of hair cells
covered with a gel cap, or cupula.
Since the fluid (endolymph) moves
slower than your head, the cap shifts
or lags behind your movement,
stimulating hair cells which send
impulses to the vestibular nerve and
the cerebellum. When the movement
stops, the fluid moves in the opposite
direction, moves the cap the other
way, causing the hair cells to slow
their signaling.
2009-2010 P. Holman
Anatomy and Physiology
The signals from the vestibule,
semicircular canals, eyes, and
proprioceptors of muscles and
tendons all provide information to the
cerebellum regarding control of
balance.
Hearing loss websites:
http://www.healthcentral.com/channe
l/408/1191.html
http://www.cdc.gov/niosh/docs/96115/diseas.html#hearings
http://www.houseearclinic.com/heari
ngloss.htm
http://www.hearingaidscentral.com/h
earingdiseasesanddisorders.asp
http://www.asha.org/public/hearing/d
isorders/causes.htm
2009-2010 P. Holman
Anatomy and Physiology
http://en.wikipedia.org/wiki/Hearing_
impairment
common sounds and decibels:
http://www.dangerousdecibels.org/tea
chers_guide/DDB_TRG_Appendices
_3.pdf
http://www.deafness-andhearingaids.net/2007/03/07/howloud-is-too-loud-decibel-levels-ofcommon-sounds/
http://www.phys.unsw.edu.au/jw/dB.
html
http://explorersposts.grc.nasa.gov/pos
t631/20072008/acoustic/AcousticSignalProc.pd
f
2009-2010 P. Holman
Anatomy and Physiology
lab:
http://www.dangerousdecibels.org/tea
chers_guide/DDB_TRG_Activities_1
0.pdf
Chemical Senses: Taste and Smell


Describe the location, structure, and function
of the olfactory and taste receptors.
Name the four basic taste sensations and list
factors that modify the sense of taste.
Developmental Aspects of the Special Senses

Describe changes that occur in the special sense organs with age.
2009-2010 P. Holman