1. Sensory System
Unit- L

2. Special Senses 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.

3. The Eye Wall of Eye is made up of 3 layers or coats
Sclera, Choroid Coat, and the Retina
SCLERA- Outer layer
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.

4. The Other Eye Cornea – Front of sclerotic coat (part of sclera)
Clear part (no blood vessels) – called the “window of the eye”
Transparent so light rays can pass through
Gets O2 and nutrients through lymph

5. I can see you…. Choroid Coat 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

6. Can you see me??
Lens
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

7. Both substances maintain eye’s spherical shape and refract light rays
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

8. Oh no!! It’s dark in here!! Retina
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.

9. Finally…the eye is almost over!
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.

11. The Eye Pathway of Vision CORNEA PUPIL LENS (Light rays are refracted)
RETINA

12. 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.

13. Can you hear me?? Middle Ear 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.
MALLEUS (hammer)
INCUS (anvil)
STAPES (stirrup)

14. I can hear you  Inner Ear
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).

16. Where does the sound go? Pathway of Hearing
Sound waves Pinna External Auditory Canal Tympanic Membrane Ossicles ( malleus, incus, & stapes) Cochlea Auditory nerve Brain

17. The Nose & Tongue 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 the cerebral cortex.

18. Common Sensory Disorders
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

19. Eye disorders Glaucoma
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

20. Common Sensory Disorders
CATARACTS
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
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.

21. Still problems with the eye
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

22. Eye Injuries 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.

23. Eye doctor = Opthamologist
Do you need glasses?
PRESBYOPIA
Lens loses elasticity, cant focus on close or distant objects
Usually occurs after age 40
Rx- bifocals
HYPEROPIA
Farsighted
Focal point beyond the retina because eyeball too short
Convex lenses help
MYOPIA
Nearsighted – can’t see far away
Eyeball too long
Concave lenses help
Eye doctor = Opthamologist

24. Still more eye problems
AMBLYOPIA
Reduction or dimness of vision
ASTIGMATISM
Irregular curvature of the cornea or lens, causing blurred vision and eye strain
Rx- corrective lenses
DIPLOPIA- double vision
STABISMUS ( cross-eyes)
Eye muscles do not coordinate their actions
Usually in children
Rx – eye exercises or surgery
Opthalmoscope = used to examine the eye

25. Disorders of the Ear Loud noise
Hearing is fragile! Loud noise over a period of time can cause hearing loss.
Symptoms- TINNITUS (ringing in ears) and difficulty understanding what people are saying
Conductive hearing loss….may be from excessive wax in ear canal

26. Disorders of the Ear OTITIS MEDIA 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

27. Other Sensory Problems
Phantom Pain
After an amputation your brain still sends signals to amputated limb. Neural pathways are still intact.
Rhinorrhea
Allergies cause constant, clear drainage from nose and down pharynx from maxillary sinuses. May cause chronic pharyngitis.

28. Other Sensory Problems
Thrush (oral yeast infection characterized by white patches on tongue and cheeks)
Antibiotics wipe out normal flora which allow fungi to flourish…vaginal and oral yeast infections are common with antibiotic use