1. Health Occupations
Special Senses

2. Functions of our special senses
Allows human body to react to environment
Enables the body to
See
Hear
Taste
Balance
Smell
Can occur because body has structures that
Receive sensation
Nerves that carry sensory messages to brain
Brain that can interpret & respond to message

3. Eye Organ that controls sight Eye Receives light rays
Transmits rays to optic nerve
Optic nerve carries rays to brain
Brain interprets rays as vision or sight

4. Protection of eye Bony socket of skull Eye lids & lashes
Partially enclosed
Eye lids & lashes
Help keep out dirt & pathogens
Lacrimal glands
Produce tears which moisten & cleanse eye
Tears flow across eye, drain through lacrimal duct into nasal cavity
Conjunctiva
Mucous membrane that protects eye
Lines eyelids & covers front of eye
Provides protection & lubrication

5. 3 main layers of eye Sclera Outermost layer Tough connective tissue
White of eye
Maintains eye shape
Extrinsic muscles
Responsible for moving eye in socket
Attach to outside of sclera
Cornea
Circular transparent part on front of sclera
Allows light rays to enter eye

6. 3 main layers of eye Choroid coat Middle layer of eye
Interlaced with many blood vessels that nourish eye
Pupil
Hole in front of choroid coat
Allows light rays in
Iris
Colored part of eye
Muscle that controls the size of the pupil & regulates amount of light entering eye

7. 3 main layers of eye Retina Innermost layer
Made of many layers of nerve cells that transmit light to the optic nerve
2 types of cells in retina
Cones
Used for light vision
Sensitive to color
Located in depression on back of retina (FOVEA CENTRALIS) which is the area of sharpest vision
Rods
Used mainly for dim or dark vision

8. Other special structures
Lens
Circular structure behind pupil
Suspended in place by ligaments
Refracts (bends) light rays so that the rays will focus on the retina

9. Aqueous humor Clear watery fluid found in anterior chamber of eye
Fills space between cornea & iris
Helps maintain forward curvature of eyeball
Bends (refracts) light rays

10. Vitreous humor Jelly like substance found in posterior chamber of eye
Fills area behind lens
Helps maintain eyeball shape
Also bends or refracts light rays

11. 1. Ciliary body & muscle
2. Suspensory
ligament
3. Conjunctiva
4. Iris
16. Retina
5. Pupil
15. Retinal arteries
And veins
6. Path of light
14. Fovea centralis
17. Anterior
Chamber
(aqeuous humor)
13. Optic
nerve
7. Cornea
12. Choroid
coat
8. Lens
11. Sclera
9. Suspensory ligament
Posterior chamber (vitreous humor)

12. Refraction of light rays
As light enters eye, it passes through a series of parts that refracts it
Rays pass through cornea, aqeuous humor, pupil, lens, & vitreous humor
Focus on fovea centralis, the area of retina that has sharpest vision and the most nerve cells
In retina, rays are picked up by rods & cones
Changed into nerve impulses
Transmitted by the optic nerve to the occipital lobe of cerebrum
Sight can be interpreted by cerebrum
If rays are not refracted correctly, vision is distorted or blurred

13. Abnormal eye conditions
Amblyopia
Lazy eye
Common in early childhood
Results in poor vision in one eye
Due to dominance in other eye
Treatment
Cover good eye to stimulate development of lazy eye
Exercises to strengthen weak eye
If untreated before 8-9 years of age
Blindness of weak eye may occur

14. Astigmatism Abnormal shape or curvature of cornea
Causes blurred vision
To correct, apply corrective lenses
Light rays focus on multiple areas of retina

15. Cataracts Normally clear lens becomes cloudy or opaque
Occurs gradually, usually result of age
May be caused by trauma
Symptoms
Blurred vision
Halos around lights
Gradual vision loss
Milky white pupil in late stages

16. Cataracts Treatment Surgical removal of lens Implant intraocular lens
New glasses or contacts

17. Conjunctivitis Pink eye Contagious inflammation of conjunctiva
Causes – bacteria or virus
Symptoms
Redness
Swelling
Pain
Pus formation
Treatment
Antibiotics, usually ointment

18. Glaucoma Results from increased intraocular pressure
Caused by excess aqueous humor in anterior chamber of eye
Common after age 40
Leading cause of blindness
Tonometer – instrument used to measure IOP, used during every eye exam
Symptoms
Loss of peripheral vision
Halos around lights
Limited night vision
Mild aching

19. Glaucoma treatment Controlled with meds
Decrease amount of aqueous humor
Improve drainage of aqueous humor
Surgery to create an opening for the flow of aqueous humor

20. Hyperopia Farsightedness Light focuses behind retina
Can see far away NOT near
Correct with glasses or contacts - convex

21. Myopia Nearsightedness
Light rays are refracted too sharply & focus in front of retina
Can see near NOT far away
Corrected by concave lenses
Can correct with surgery or lasers

22. Presbyopia Farsightedness Caused by loss of lens elasticity
Occurs as a result of normal aging
Treated with reading glasses

23. Strabismus Eyes do not focus or move together
Eyes may be cross-eyed inwardly, outwardly, or up & down
Caused by muscle weakness in one or both eyes
Treatment
Eye exercises
Covering good eye
Corrective lenses
Surgery on muscles moving eye

24. Ear Organ that controls hearing & balance
3 main sections – outer, middle, inner
Hearing
Transmits impulses from sound waves to auditory nerve (vestibulocochlear)
Auditory nerve carries impulses to brain
Brain interprets as hearing

25. Outer ear Auricle or pinna Auditory canal Tympanic membrane
Visible part of ear
Elastic cartilage covered by skin
Leads to canal called the external auditory meatus and auditory canal
Auditory canal
Contains special ceruminous glands producing cerumin (wax) for protection
Sound waves travel through this to reach tympanic membrane
Tympanic membrane
Separates external & middle ear
Vibrates when sound hits it
Transmits sound waves to middle ear

26. Middle Ear Small space or cavity in temporal bone
Contains 3 small bones (ossicles)
Malleus
Incus
Stapes
Bones connected & transmit sound waves from tympanic membrane to inner ear
Eustachion tube
Tube connecting middle ear to pharynx that allows air to enter the middle ear
Helps to equalize pressure on both sides of tympanic membrane

27. Inner ear Most complex part of ear Oval window Vestibule Cochlea
Membrane separating inner & middle ear
Vestibule
First section acting as entrance to 2 other parts of inner ear
Cochlea
Snail shaped
Contains delicate hair like cells that make up ORGAN OF CORTI
Receives sound waves & transmits impulses to auditory nerve

28. Inner ear Semicircular canals Contain liquid & hair like cells
Bend when liquids move with head & body movements
Impulses sent to cerebellum to help maintain balance & equilibrium

29. Not pictured
Pinna or auricle
4. Malleus
5. Incus
7. Semicircular
canals
8. Auditory nerve
9. Cochlea
2. External auditory canal
10. Oval
window
11. Eustachion
tube
3. Tympanic
membrane
6. Stapes

30. Abnormal conditions Hearing loss – 2 types Conduction
Caused by sound waves not being conducted to inner ear
Causes
Cerumen plug
Foreign body obstruction
Otosclerosis
Infection
Ruptured tympanic membrane
Treatment
Eliminate cause
Surgery
Hearing aids

31. Sensory hearing loss Caused by damage to inner ear or auditory nerve
Usually can NOT be corrected
Cochlear implants can improve severe hearing loss

32. Meniere’s disease
Collection of fluid in labyrinth of the inner ear & degeneration of hair cells in cochlea & vestibule
Symptoms
Severe vertigo or dizziness
Tinnitus (ringing in ears)
N&V
Loss of balance & tendency to fall
Treatment
Drugs to reduce fluids & antihistamines
Drainage of fluid
Surgery to destroy cochlea in severe cases (causes permanent deafness)

33. Otitis externa Inflammation of external auditory canal
Variety of causes
Swimmer’s ear
Inserting foreign objects (bobby pins, fingernails, cotton swabs)
Treatment
Antibiotics
Warm moist compresses
Pain meds

34. Otitis media Inflammation or infection of middle ear
Causes – bacteria or virus
Frequently follows sore throat because organisms can enter ear through Eustachion tubes
Susceptible –
Infants & young children
Eustachion tube is angled differently than in adults & secretions from nose & throat accumulate in middle ear
This causes inflammatory response that causes tube to swell shut

35. Otitis media Symptoms Treatment Severe pain Fever Vertigo Dizziness
N & V
Buildup of fluid in middle ear
Treatment
Antibiotics & pain meds
Myringotomy & tubes

36. Otosclerosis Stapes becomes immobile & causes conductive hearing loss
Symptoms
Gradual hearing loss
Tinnitus
vertigo
Treatment
Surgical removal of stapes
Insertion of artificial stapes

37. Taste Dependent on taste receptors located on tongue Four main tastes
Tongue is mass of muscle tissue with projections called papillae
Papillae contain taste buds which are stimulated by flavors & moistened by saliva
Four main tastes
Sweet & salty – tip of tongue
Sour – sides of tongue
Bitter – back of tongue
Influenced by smell

38. Smell
Nose is organ
Determined by olfactory receptors in upper part of nasal cavity
Impulses from receptors are carried to brain by olfactory nerve
Sense of smell closely related to taste
Smell much more sensitive
Human nose can detect over 6,000 different smells

39. Skin & general senses
General sense receptors for pressure, heat, cold, touch, & pain located throughout body in skin & connective tissue
Each receptor perceives only 1 type of sense
Messages from receptors allow human body to respond to environment
Helps body to react to conditions that could cause injury