Download SPECIAL SENSES

Five Senses (listed in book)

Hearing
Sight
Taste
Smell
Balance Maintenance

However, Touch is often known as the 5th sense
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The special senses allow the human body to react
to the environment.
Steps to Responding
to a Sensory Message
Receive the sensation
2. Nerves carry the sensory message to the brain
3. The brain interprets and responds
1.
The Eye

The organ that controls the special sense of sight.
Vision is considered to be the most important sense.
About 90% of the information about a person’s
surroundings reaches the brain through the eyes.
Main Layers of the Eye
Sclera
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Outermost Layer
Tough connective tissue
Called “whites” of the eye
Help to maintain the shape of the eye
Includes:
a. Extrinsic Muscles - moves the eye within the socket
b. Cornea – a circular transparent part at the front of the
sclera which allows light to enter the eye
Main Layers of the Eye
Choroid Coat
Middle Layer
 Contains blood
vessels

Includes:
 Pupil – hole in front of choroid coat which
allows light rays to enter
 Iris – colored portion of the eye, controls
the size of the pupil, regulates the light
Main Layers of the Eye
Retina
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Innermost layer
Contains special cells
Transmits light impulses
Special Cells include:
 Cones – used mainly for light vision, sensitive to
color, located at the Fovea Centralis where the
sharpest vision is located
 Rods – used for dark or dim vision
View of the Retina
Other Structures of the Eye
Lens:
 Circular structure located behind the pupil
 Refracts or bends light so the rays will
focus on the retina
Aqueous Humor:
 Clear, watery fluid
 Fills the space between the cornea and iris
 Maintain forward curvature of the eye
 Refracts light rays
Other Structures of the Eye
Vitreous Humor:
 Jellylike substance
 Fills the area behind the lens
 Maintain the shape of the eyeball
 Also, refracts light rays
What Nerve is Responsible for Vision?

The Optic Nerve
Refraction of Light Rays
Light passes thru the eye in this order:
1. Cornea
2. Aqueous Humor
3. Pupil
4. Lens
5. Vitreous Humor
6. Retina
In the retina, the light rays are picked up by the rods & cones.
Finally, the nerve impulses are sent to the optic nerve to
the occipital lobe of the brain where the sight is interpreted.
What does 20/20 vision mean?

If you have 20/20 vision, it means
when you stand 20 feet away from the
eye chart that you can see what the
"normal" human being who has good
vision can see.

If you have 20/40 vision, it means that
when you stand 20 feet away from the
chart you can see what a normal
human can see when standing 40 feet
from the chart (letters will be larger).

20/200 is the cutoff for legal blindness
in the United States.
Snellen Eye Chart
What Gland Secretes Tears?

Lacrimal Gland

Tears produced in the lacrimal glands
constantly clean the eye and keep it moist.
What Protects the Eye?
Bony Socket
2) Eyelids
3) Eyelashes
4) Lacrimal Glands (tears)
5) Conjunctiva (thin membrane that lines
1)
the eyelids and covers the front of
the eye)
Eye Disorders

Amblyopia – poor vision in one eye caused by
dominance of the other eye, “lazy eye”
Eye Disorders

Astigmatism – abnormal shape or
curvature of the cornea causing blurred
vision.
Eye Disorder

Cataract – lens becomes cloudy as a
result of aging or trauma.
Eye Disorder

Conjunctivitis – infection of the
conjunctiva, “pink eye”
Eye Disorder

Glaucoma – condition resulting from
an increased intraocular pressure
(inside the eye)
Eye Disorders

Hyperopia –
farsightedness, light
rays are not refracted
properly, the image
focuses behind the
retina.

Presbyopia – also
farsightedness from
loss of elasticity in
the lens.
Eye Disorders

Myopia – nearsightedness, occurs when
light rays are refracted too sharply and
the image focuses in front of the retina.
Myopia
 Image focuses in
front of the retina
and image is
blurred.
 Myopia corrected
brings image
back to the
retina.
Eye Disorders

Strabismus – condition in
which the eyes do not move
or focus together, “crosseyed”
The Ear
The organ that controls the
special sense of hearing and
balance.
 The ear transmits impulses
from sound waves to the
hearing nerve.

Divided into 3 main sections:
 Outer Ear
 Middle Ear
 Inner Ear
Outer Ear
Contains:
a) Pinna or Auricle which is the visible part of the
ear (cartilage covered with skin)
a)
External Auditory Meatus or Auditory Canal that
has special ceruminous glands which produce
wax called cerumen to protect the ear.
a)
Tympanic Membrane which separates the
external ear and the middle ear. It vibrates when
sound waves hit it.
Semicircular Canal
View of Eardrum
Middle Ear
Located in the temporal bone
Contains Ossicles which are 3
small bones:
1. Malleus
2. Incus
3. Stapes
These bones help to transmit
sound waves from the
tympanic membrane to the
inner ear.
Middle Ear (cont)

Eustachian tube connects the middle
ear to the pharynx or throat. This tube
helps equalize air pressure on both
sides of the tympanic membrane.
Inner Ear
Most Complex part of the ear
Contains:
a) Oval Window – separates the middle ear and
the inner ear
b) Vestibule – entrance of the inner ear
c) Cochlea – shaped like a snail’s shell and
contains hair-like cells in the Organ of Corti
d) Semicircular Canals – contains a liquid and
delicate hair-like cells that bend when the
liquid moves with head or body movements
Hearing Nerve


The nerve that is
responsible for hearing
is the Auditory Nerve.
The Cochlea transmits
impulses from the
sound waves to the
auditory nerve that
carries the impulses to
the temporal lobe of the
cerebrum where they
are interpreted as
hearing.
The Ear
What is the membrane between the
outer ear and the middle ear?
 Tympanic Membrane
What is the membrane between the
middle ear and the inner ear?
 Oval Window
The Semicircular Canals send
impulses to the cerebellum of
the brain to help maintain our
sense of balance and equilibrium.
Ear Disorders
Hearing Loss – inability
to hear correctly due to
a Conductive or Sensory
problem.

Causes of Conductive Hearing Loss may
include wax plug, foreign body, infection, or
ruptured tympanic membrane.
 Causes of Sensory Hearing Loss may include
damage to inner ear or auditory nerve.
Ear Disorders (cont)
Otitis Externa – inflammation
of the external auditory
canal; often a problem with
swimmers (known as
Swimmer’s Ear)
The Ear Band-It helps
to prevent water from
getting into the ears.
Ear Disorders
Otitis Media – inflammation
or infection of the middle ear
These middle ear infections are common in
children. If a child has repeated ear infections
or fluid build-up in the ears, then an ear tube
may be needed to allow the eardrum to equalize
the pressure.
Tubes for Ear Infections

Doctors suggest tubes for children who have
repeat ear infections or when fluid stays behind the
eardrum. Ear tubes are plastic and shaped like a
hollow spool. This surgery is called a myringotomy.
Tubes can help with ear infections because they:
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Allow air to enter the middle ear.
Allow fluid to flow out of the middle ear through the
Eustachian Tube.
Clears the fluid from the middle ear and can restore
hearing.
Prevent future buildup of fluid in the middle ear while they
are in place.
Decreases the feeling of pressure in the ears, which reduces
pain.
Eventually, the tubes will move out of the eardrum and
fall into the ear canal.
Ear Disorders

Otosclerosis – a condition in which the
stapes becomes immobile causing
conductive hearing loss
Taste
The tongue is a mass
of muscle tissue with
projections called
papillae which contain
taste buds.
 The receptors in the
taste buds send a
signal to the brain to
detect the flavor of
the food.
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Taste Buds
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The average human has about 10,000
taste buds; however, they're not all on
the tongue. Some are under the tongue;
some are on the inside of the cheeks;
some are on the roof of the mouth.
Some can even be found on the lips;
these are especially sensitive to salt.
Taste – Interesting Facts
Taste is about 75% smell.
 A person cannot taste food unless it is mixed
with saliva. For example, if strong-tasting
substance like salt is placed on your dry
tongue, you will not be able to taste it until it
starts to dissolve.
 Every person has a unique tongue print.
 Butterflies taste with their feet.

Four Main Taste on the Tongue
Sweet – located on the
tip of the tongue
 Salty – located on the
front upper sides of the
tongue
 Sour – located on the
sides of the tongue
 Bitter – located on the
back of the tongue

Smell
The nose is the organ of smell
 Olfactory receptors in the upper part of
the nasal cavity carry impulses to the
Olfactory Nerve of the brain.

Smell – Interesting Facts
Women are born better smellers than men and
remain better smellers over life.
 Smell function falls off in men after their
mid-50s, a decade earlier than in women.
 The smell of lavender can help with insomnia
and sleep disorders.
 The aroma of green apples can help control
appetite.
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Smell

The sense of smell is
closely related to the
sense of taste.

How many smells can
a human detect?
Over 6,000 different
smells
General Senses
Located throughout the body
Includes:
1. Pressure
2. Heat
3. Cold
4. Touch
5. Pain
Works Cited:
Diversified Health Occupations, 7th Edition
by Louise Simmers
 http://www.homeworkspot.com/know/howmanytastebu
ds.htm
 http://www.medicinenet.com/ear_tubes/article.htm
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Created by: Kathy Vidal
Health Science Technology