Transcript Senses Power Point

Senses
Five Senses
 Smell
 Taste
 Balance
 Vision
 Hearing
or equilibrium
Smell
 Olfaction:
provided by
paired olfactory organs,
located in roof of nasal
cavity on either side of the
nasal septum
 A German Shepherd has
olfactory receptor surface 2
times greater than ours
 When olfactory receptors
are stimulated, nerve
impulses are relayed to the
CNS through the olfactory
nerve
Taste
 Taste
receptors are found on superior
surface of the tongue, clustered together
to form taste buds
 Four primary taste sensations: sweet, salt,
sour, bitter
Taste Buds
Balance and Equilibrium
 Receptors
for balance and equilibrium
are housed in the ear
The Eye
 Located
in the orbits
 Orbits are formed by 7
skull bones
 Sphere measuring
about one inch in
diameter
 About 1/6 of anterior
surface can be seen
 Other 5/6 of the eye is
enclosed and
protected by a
cushion of fat and orbit
External Accessory Structures
6
external eye
muscles
 They attach to
outer surface of
eye
 They allow for
movement of
eyeball
 They are
controlled by
cranial nerves
Eyelids
 Close
firmly to protect
the delicate surface of
the eye
 Continual blinking
movements keep
anterior surface
lubricated and free from
dust and debris
 Contain sweat and
sebaceous glands, if
infected=sty
 Hairs of eyelashes
prevent foreign particles
and insects from
reaching surface of eye
 Eyebrows divert sweat
Conjunctiva
 Protects
eyeball
 Lines interior surface of
eyelids
 Covers outer surface of
eyeball
 Transparent mucus
membrane
 Contains many nerve
endings, very sensitive
 *Considered to be
accessory*
Lacrimal Apparatus
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Tear glands
Located above and to outer part of
each eye
Produces tears that flow over eye when
blinked, moistened and lubricate eye
Sclera: outer layer
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*White outer covering “white of the
eye”
Tough and Fibrous connective tissue
Provides protection and serves as an
attachment site for the eye muscles
Portion of sclera is cornea
Choroid: middle layer
 Between
the retina and sclera
 Composed of layers of blood
vessels(vascular coating) that nourish the
back of the eye
 Supplies blood , oxygen, and nutrients to the
eyeball
Retina: inner layer of the eye
 Contains
millions of
receptor cells
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Rods and Cones
 Rods
and cones
are called
receptor cells
because they
respond to light
Rods
 The
receptors for
night vision or dim
light
 Interfering with rod
function leads to
night blindness
 Night blindness
usually a
deficiency in
vitamin A
Cones
 *Receptors
for
daylight and color
 Three variations of
cones, each type is
most sensitive to
one of the primary
colors, red, green,
blue
 Lack of all 3 cone
types results in total
color blindness
which is very rare
almost exclusively in
males
Color Blindness Test
Optic Nerve
 *Visual
impulses are
sent to the brain
 Rods and cones are
distributed over entire
retina except where
optic nerve leaves the
eyeball

the “blind spot”
 We
aren’t aware of the
blind spot because our
eye are always moving
Cornea
 Transparent
anterior portion
 First structure of eye through
which light passes
 Well supplied with nerve
endings, mostly pain fibers
 When touched, blinking and
increased tearing occur
 Most exposed part of the eye,
vulnerable to damage
 Has no blood vessels, tissue
can be transmitted from one
person to another without
worry of rejection
Ciliary Body/Muscle
 *Controls
shape of lens
 Important in the focusing process
 Supports lens through suspensory ligaments
 Secrete aqueous humor
Lens
 *Function
is to focus the image on the
sensory receptors in the retina
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Near or far away
 Focusing
depends on refraction, or
bending of light from the object
 Divides eye into two chambers: aqueous
chamber and vitreous
Aqueous Chamber
 *Anterior
cavity between the lens and the
cornea
 Filled with aqueous humor, a clear watery
fluid
 Provides nutrients for the lens and cornea
 *Maintains intraocular pressure and shape
of the eye
 If pressure is blocked and pressure
increases leads to glaucoma
Vitreous Chamber
 Posterior
cavity
 Occupies entire orbit
behind lens
 Filled with vitreous
humor
 Helps prevent the
eyeball from
collapsing inward
 Helps maintain
pressure and shape
Iris
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Gives us our eye color.
Front portion of choroid
Formed from circular and
radial smooth, involuntary
muscles
*Regulates amount of
light entering the eye so
we can see as clearly as
possible
In close vision and bright
light, circular muscles
contract, pupil constricts
In distant vision and dim
light, radial fibers contract
to enlarge or dilate pupil,
letting in more light
Pupil
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Rounded opening of the
iris
Looks black because inner
eye is dark
Size determines how much
light will enter the eye
*Flashlight
Test*
What Do Glasses and Contact
Lenses Really Do? Eye Conditions
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47% of people in U.S. wear contacts
or glasses
In normal eye, the ciliary muscles
are relaxed and lens is flattened,
the distant image is focused on
retina
Irregularities in shape of lens or
cornea can affect the clarity of the
visual image (astigmatism),
corrected with glasses.
Myopia (nearsightedness): the
eyeball is too deep, image of
distant object will form in front of
retina and be blurry. Vision at close
range will be normal because the
lens will be able to round up as
needed
Eye Conditions Cont.
 Hyperopia
(farsightedness):
If eyeball is too shallow this
will occur. The ciliary muscles
must contract to focus even
a distant object on the
retina, and at close range
the lens cannot provide
enough refraction
 Presbyopia (old man’s eye):
Older individuals become
farsighted as their lenses
become elastic.
Vision Test
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*Vision tests are commonly
done using a Snellen Chart.*
*20/20 vision:* rating the clarity
of vision. A person is seeing
details at a distance of 20 feet
as clearly as a “normal”
individual would.
20/15: Is better than average
for at 20 feet the person is able
to see details that would be
clear to a normal eye only at a
distance of 15 feet
Legally blind: 20/200
Ophthalmoscope
 Instrument
use to
examine the interior
of the eye
The Ear
Two Sensory Functions of the Ear
 Equilibrium:
informs us of
the position of the body in
space by monitoring
gravity, acceleration, and
rotation
 Hearing: enables us to
detect and interpret sound
waves
 Senses of equilibrium and
hearing are provided by
inner ear
3 Parts of the Ear
 Basic
receptors for these senses are
ciliated cells called hair cells. Movement
of the cilia cause the hair cells to produce
nerve impulses which are sent to the brain
via the eighth cranial nerve.
External Ear
 *Pinna/auricle:*
external cartilaginous flap
that catches sound waves. Surrounds the
entrance to external auditory canal.
External Ear
 Auditory
canal: short,
narrow chamber lined
with fine hairs and sweat
glands.
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Hair helps prevent the
entry of foreign objects
and insects.
 Ceruminous
glands
(sweat glands) secrete
cerumen (ear wax) which
slows growth of
microorganisms.
Middle Ear
 Sound
waves are
collected and conducted
through the air on their
way to the tympanic
membrane (eardrum)
 *Tympanic membrane:* is
a thin sheet that
separates the external
ear from the middle ear
 Process of hearing begins
when sound waves enter
the auditory canal
Middle Ear
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*Separated from the
external auditory canal
by the tympanic
membrane*
Connects middle ear
with nasopharynx
called the auditory
tube or Eustachian
tube.
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This tube serves to
equalize the pressure
on either side of the
eardrum but also
provides a path for
microorganisms to enter
and cause middle ear
infections
Middle Ear-Ossicles
 *Three
tiny ear bones*
 These bones connect the tympanic membrane with
the receptors of the inner ear and amplify the
sound about 20 times
 Malleus (hammer): is attached to the inside surface
of the tympanum.
 Incus (anvil): attaches malleus to the inner stapes.
 Stapes (stirrup): is attached to the oval window, a
membrane in the inner ear
 Vibration of the ear drum causes the three ear
bones to move, and rocks the stapes against the
oval window
Inner Ear
Inner ear structures and
functions
 Senses
of equilibrium and hearing are
provided by the receptors within the inner
ear
 Receptors for both of these lie in a
network of fluid-filled tubes and chambers
known as membranous labyrinth which
contains a fluid called endolymph
 Bony labyrinth: surrounds and protects
membranous labyrinth
 Perilymph: fluid that flows between the
bony and membranous labyrinth
 Sound is conducted through the fluid
Three Sub-Divisions Of The
Inner Ear
 *Semicircular
canals: balance*
 Vestibule: balance
 Cochlea: hearing
Semicircular Canals
 Provide
information concerning
rotational movement of the head
 Each canal encloses a slender
semicircular duct that contains
endolymph and a sensory receptor
 Each semicircular duct responds to
one of three possible movements:
horizontal rotation: shaking the
head “no”, front to back: nodding
“yes”, side to side: tilting the head
 Continuous movement of the fluid
can lead to motion sickness
Vestibule
 Between
the semicircular canals and
cochlea
 Provide the sensation of gravity and
acceleration
 Provide information on which way is up or
down, helps keep our heads erect
Cochlea
 Function
in hearing
 Looks like a snail
 *Contains Organ of Corti: extend along
the entire length of the coiled cochlear
duct, changes vibrations to nerve
impulses
 *FYI: Buzzing or Ringing in the ears is
called “Tinnitus.”*
Let’s put it all together!
 How
Your Ears Work