1. Chapter 15
Special Senses

2. Ear Notes

3. Definitions Pinna— Elastic cartilage Tympanic membrane— eardrum
Ear ossicles— malleous, incus, stapes
Two membranes in inner ear— oval window, round window
Eustachian tube— connects ear to throat
Function— equalize pressure

4. Inner Ear Labyrinth Lymphs Bony Membranous Endolymph Perilymph
Cochlea: Hearing
Vestibule: Balance
Semicircular canals: Balance
Membranous
Lymphs
Endolymph
In membranous labyrinth
Perilymph
Space between membranous and bony labyrinth

5. Hearing
Organ of hearing:
How we hear—happens within the cochlea

6. Effect of Sound Waves on Cochlear Structures

7. Hearing Process Waves move perilymph
Perilymph moves vestibular membrane that moves endolymph
Endolymph moves tectorial membrane which moves the hair cells
Hair cells send impulse to nerves & the brain
Sound waves leave through round window

8. Auditory Function Vibrations produce sound waves
Volume or loudness : number of hairs stimulated
Pitch: Function of wave frequency

9. Balance Static Kinetic Evaluates position of head relative to gravity
Detects linear acceleration and deceleration
Kinetic
Evaluates movements of head
3 semicircular canals
Ampulla
endolymph moves when head moves

10. Semicircular Canals Contain fluid and hair
Movement moves fluid & hairs
Sends impulse to brain

11. Ear Disorders  Tinnitus Motion sickness Otitis Media Earache
Ringing, clicking, whistling in ear due to disorders in middle or inner ear
Motion sickness
Dysfunctions caused by stimulation of semicircular canals during motion
Otitis Media
Infections in the middle ear
Earache
Results from otitis media, dental abscesses, TMJ pain

12. The Eye

13. Structure of the Eye Layers and coats Fibrous Tunic: Outer
Sclera—tough, white, outer portion; maintains shape,
protects internal structures, provides muscle attachment
point; continuous with cornea
Cornea—transparent portion of anterior eye; avascular; bends & refracts light
Vascular Tunic: Middle
Choroid—middle layer; blood vessels & darkly pigmented
Ciliary body—holds ciliary muscles (smooth) attached to lens w/ suspensory ligaments to control lens shape
Lens- transparent; bioconvex
Iris—colored, smooth muscle ring with the pupil in the middle; controls light entering pupil

14. Structure of the Eye Continued
Retina—Inner
Retina-incomplete, innermost layer; nervous layer (contains neurons sensitive to light)
Rods (black & white)
Cones (color)
Fovea Centralis/Macula lutea- where light is focused; see fine images (area of greatest acuity)
Optic disc (no photoreceptor cells) AKA Blind Spot

15. Cavities (compartments) in the Eye
Anterior cavity—between the lens and cornea
Filled with aqueous humor—clear, watery fluid
Helps maintain intraocular pressure
Glaucoma—too much intraocular pressure due to too much aqueous humor 
Posterior cavity—behind the lens and posterior portion of the eye
Filled with vitreous humor—soft, gelatin-like substance
Helps with intraocular pressure to prevent collapse

16. Muscles of the Eye
Extrinsic eye muscle—skeletal muscles that move the eyeball
Intrinsic eye muscle—smooth muscles in the eye—involuntary
Iris
Ciliary body

17. Accessory structures
Eyebrows & eyelashes—keep some foreign particles out of eye
Eyelids—help with lubrication
Conjunctiva-mucus membrane lining the lid
(AKA Pink eye (conjunctivitis); caused by an infection or irritation 
Closes from outside to in/ top to bottom

18. Lacrimal Apparatus Lacrimal apparatus Lacrimal Canaliculi Punctum
Lacrimal Gland: Produces tears to moisten, lubricate, wash
Lacrimal Canaliculi
Collects excess tears
Punctum
Lacrimal Sac
Nasolacrimal duct
Opens into nasal cavity

19.  Concept Review  What are the 3 main layers of the eye?
-sclera, choroid, retina
What are the 3 accessory structures and describe their function?
-eyebrows, eyelashes, & eyelids (protection &
lubrication)
Where are tears formed and where do they go?
-lacrimal gland, nasalacrimal duct

20. How we see (4 main steps) Formation of Vision on the Retina
1. Refraction of light rays
cornea, aqueous humor, lens, vitreous humor
2. Accommodation of lens
Increase in curvature to achieve greater refraction on near objects
Emmetropia: Normal resting condition of lens
Far vision: 20 feet or more from eye
Near Vision: Closer than 20 feet
3. Constriction of pupil
Iris contracts to limit the amount of light that enters the eye

21. How we see Continued… Formation of Vision on the Retina
4. Convergence of eyes
Light must hit the same spot of the retina on both eyes to see only one object
Both eyes are directed on the object at the same angle
Single binocular vision —seeing one object with two eyes

22. Eye Disorders  Myopia: Nearsightedness Retinal detachment
Focal point too near lens, image focused in front of retina
Hyperopia: Farsightedness
Image focused behind retina
Presbyopia
Degeneration of accommodation, corrected by reading glasses
Astigmatism: Cornea or lens not uniformly curved
Strabismus: Lack of parallelism of light paths through eyes
Retinal detachment
Can result in complete blindness
Glaucoma
Increased intraocular pressure by aqueous humor buildup
Cataract
Clouding of lens
Macular degeneration
Common in older people, loss in acute vision
Diabetes
Dysfunction of peripheral circulation

23. The Mouth

24. Sense of Taste Specific sense organ– TASTE BUDS
Located on projections of tongue called papillae

25. Structure of a Taste Bud
Gustatory cell—contain tiny, cilia-like gustatory hairs
Taste pore—opening in the papillae that is bathed in saliva
*The chemicals of food must dissolve in the saliva to stimulate the hairs to start an impulse.*

26. Primary Tastes

27. The Nose

28. Sense of Smell Olfactory organs Sensory hairs Olfactory cells
Olfactory nerves
Olfactory bulb
Olfactory tract

29. Smelling Substance must be: Able to become a gas
Water soluble or very small
Lipid soluble (to get into membrane)

30. Effects of Aging on the Special Senses
Slight loss in ability to detect odors
Decreased sense of taste
Lenses of eyes lose flexibility
Development of cataracts, macular degeneration, glaucoma, diabetic retinopathy
Decline in visual acuity and color perception