Download Senses

Sensory System
Unit- L
Special Senses
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The Eye
 1” in diameter
 Protected by orbital
socket of skull,
eyebrows, eyelashes
and eyelids.
 Bathed in fluid from
Lacrimal Glands
 ( tears empty into
nasal cavity)
 Conjunctiva – thin
membrane that lines
the eyelids and covers
part of the eye.
The Eye
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Wall of Eye is made up of 3 layers or coats
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Sclera, Choroid Coat, and the Retina
SCLERA- Outer layer
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White of the eye
Tough, fibrous capsule helps maintain shape
of eye and protects the structure within.
EXTRINSIC MUSCLES- muscle responsible for
moving the eye that are attached to the
sclera.
The Other Eye
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Cornea – Front of
sclerotic coat (part of
sclera)
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Clear part (no blood
vessels) – called the
“window of the eye”
Transparent so light
rays can pass through
Gets O2 and nutrients
through lymph
I can see you….
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Choroid Coat
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Middle layer
Contains blood vessels
Circular opening in front is the PUPIL
Colored, muscular layer surrounding pupil is
IRIS
INTRINSIC MUSCLES - change size of iris to
control amount of light entering through the
pupil – exposed to light = constriction
Can you see me??
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Lens
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Crystalline structure located behind iris and pupil –
focuses light rays on retina – function is
accommodation = adjusting for near / far vision
Elastic, disc-shaped, biconvex
Situated between the anterior and posterior
chambers
Hey…where did you go??
ANTERIOR CHAMBER filled with AQUEOUS
HUMOR, a watery fluid.
POSTERIOR CHAMBER filled with transparent,
jellylike substance - VITREOUS HUMOR
Both substances maintain eye’s spherical shape
and refract light rays
Oh no!! It’s dark in here!!
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Retina
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Innermost layer – 3rd coat of the eye – located
between the posterior chamber and choroid coat
Light rays focus an image on the retina
The image then travels to the cerebral cortex via the
OPTIC NERVE.
If light rays do not focus correctly on the retina, the
condition may be corrected with properly fitted
contact lenses, or eyeglasses, which bend the light
rays as required.
Finally…the eye is almost over!
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Retina contains specialized cells, visual
receptors - rods and cones
RODS- sensitive to dim light…problems
driving at night….damage to rods
CONES – sensitive to bright light – responsible
for color vision
OPTIC DISC- on the retina, known as the
blind spot- nerve fibers gather here to form
the optic nerve, no rods or cones.
The Eye
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Pathway of Vision
LIGHT
RETINA
CORNEA
RODS & CONES
( Pick up stimulus)
PUPIL
LENS (Light
rays are refracted)
OPTIC NERVE
BRAIN
The Ear
Outer Ear
 PINNA (AURICLE)outer ear, collects
sound waves
 EXTERNAL AUDITORY
CANAL- ear canal
 CERUMEN- earwax,
protects the ear
 TYMPANIC
MEMBRANE- ear drum,
separates outer and
middle ear.
Can you hear me??
Middle Ear
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Cavity in temporal bone
Connects with pharynx by EUSTACHIAN TUBE which equalizes pressure in the middle ear with
outside atmosphere.
Bones in middle ear transmits sound waves from
ear drum to inner ear.
1.
2.
3.
MALLEUS (hammer)
INCUS (anvil)
STAPES (stirrup)
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I
can
hear
you
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Inner Ear
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Contains spiral shaped organ of hearing - the
COCHLEA
The cochlea contains a membranous tube, the
cochlear duct- which is filled with fluid that vibrates
when sound waves are transmitted by the stapes.
ORGAN OF CORTI- in the cochlea - delicate hairlike
cells that pick up vibrations of fluid and transmit them
as a sensory impulse along the auditory nerve to the
brain.
SEMICIRCULAR CANALS- three structures in the inner
ear, contain liquid that is set in motion by head and
body movements- impulses sent to cerebellum to help
maintain body balance (equilibrium).
Where does the sound go?
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Pathway of Hearing
Sound waves
Pinna
External
Auditory Canal
Tympanic Membrane
Ossicles ( malleus, incus, & stapes)
Cochlea
Auditory nerve
Brain
The Nose & Tongue
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Nose
 Smell accounts for 90% of taste
 Tissue in the nose, olfactory
epithelium, contains specialized nerve
cell receptors.
 Those receptors stimulate the
OLFACTORY NERVE to the brain.
Tongue
 Mass of muscle tissue
 Bumps, projections, on the surface
are papilla, they contain the TASTE
BUDS.
 Receptors in the taste buds send
stimuli through 3 cranial nerves to
Common Sensory Disorders
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Disorders of the Eye
CONJUCTIVITIS
 Pink eye
 Inflammation of conjunctival
membranes in front of the
eye
 Redness, pain, swelling, and
discharge
 Highly contagious
 Rx- antibiotic eye drops
Eye disorders
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Glaucoma
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Excessive intraocular pressure causing destruction of
the retina and atrophy of the optic nerve
Caused by over production of aqueous humor, lack of
drainage, or aging.
Symps- develop gradually – mild aching, loss of
peripheral vision, halo around the light
TONOMETER- measures intraocular pressure
Rx – drugs or laser surgery to decrease intraocular
pressure
Common Sensory Disorders
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CATARACTS
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Lens of eye gradually becomes cloudy
Frequently occurs in people over 70
Causes a painful, gradual blurring and loss of vision
Pupil turns from black to milky white
Rx- surgical removal of the lens
Macular Degeneration
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Eye disorder that occurs with aging
The macula ( part of the retina responsible for sharp color
vision) degenerates
Vision is reduced but usually doesn’t cause total blindness.
Still problems with the eye
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Detached Retina
 May occur with aging- accident can cause it at
younger age
 Retina detaches from choroid
 Symps- loss of peripheral vision and then central
vision
 Rx- laser or freezing technique
STY ( HORDEOLUM)
 Abscess at the base of an eyelash (in sebaceous
gland)
 Symps- red, painful and swollen
 Rx- warm, wet compresses
Eye Injuries
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Tears are effective in cleaning the eye
If glass or fragments get in eye, cover both eyes
and see medical treatment. (DO NOT remove
the object)
Night blindness = NYCTALOPIA- due to inactive
rods
Color blindness- cones are affected – genetic
disorder that carried by the female and
transmitted to males.
Do you need glasses?
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PRESBYOPIA
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HYPEROPIA
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Lens loses elasticity, cant focus on close or distant objects
Usually occurs after age 40
Rx- bifocals
Farsighted
Focal point beyond the retina because eyeball too short
Convex lenses help
MYOPIA
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Nearsighted – can’t see far away
Eyeball too long
Concave lenses help
Still more eye problems
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AMBLYOPIA
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Reduction or dimness of vision
ASTIGMATISM
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Irregular curvature of the cornea or lens, causing blurred vision
and eye strain
Rx- corrective lenses
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DIPLOPIA- double vision
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STABISMUS ( cross-eyes)
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Eye muscles do not coordinate their actions
Usually in children
Rx – eye exercises or surgery
Disorders of the Ear
Loud noise
Hearing is fragile! Loud noise over a
period of time can cause hearing loss.
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Symptoms- TINNITUS (ringing in ears) and
difficulty understanding what people are
saying
Conductive hearing loss….may be from
excessive wax in ear canal
Disorders of the Ear
OTITIS MEDIA
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Infection of the middle ear
Often a complication of a common cold in
children
Rx- antibiotics
If chronic or if fluid builds up- MYRINGOTOMY
(opening in the tympanic membrane) with
tubes inserted will relieve the pressure.
Sxs – fever, pain, fluid drainage
Other Sensory Problems
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Phantom Pain
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After an amputation your brain still sends
signals to amputated limb. Neural pathways
are still intact.
Rhinorrhea
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Allergies cause constant, clear drainage from
nose and down pharynx from maxillary
sinuses. May cause chronic pharyngitis.
Other Sensory Problems
Thrush (oral yeast infection characterized by white patches on
tongue and cheeks)
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Antibiotics wipe out normal flora which allow
fungi to flourish…vaginal and oral yeast
infections are common with antibiotic use