Download Senses Notes

Definitions

Pinna— Elastic cartilage
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Tympanic membrane— eardrum
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Ear ossicles— malleous, incus, stapes


Two membranes in inner ear— oval window,
round window
Eustachian tube— connects ear to throat
 Function—
equalize pressure
Inner Ear

Labyrinth

Bony
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
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Cochlea: Hearing
Vestibule: Balance
Semicircular canals:
Balance
Membranous
Lymphs

Endolymph


In membranous labyrinth
Perilymph

Space between
membranous and bony
labyrinth
Hearing


Organ of
hearing:
How we hear—
happens within
the cochlea
Effect of Sound Waves on Cochlear Structures
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

Auditory Function

Vibrations produce sound waves
 Volume
or loudness : number of hairs stimulated
 Pitch: Function of wave frequency
Balance

Static
 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
Semicircular Canals
Contain fluid and hair
 Movement moves fluid & hairs
 Sends impulse to brain

Ear Disorders 

Tinnitus
 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

Earache
 Results
in the middle ear
from otitis media, dental abscesses, TMJ pain
The Eye
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
Structure of the Eye Continued

Retina—Inner

Retina-incomplete,
innermost layer; nervous
layer (contains neurons
sensitive to light)



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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
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
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
Accessory structures

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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
Lacrimal Apparatus

Lacrimal apparatus


Lacrimal Gland: Produces
tears to moisten,
lubricate, wash
Lacrimal Canaliculi

Collects excess tears

Punctum

Lacrimal Sac

Nasolacrimal duct

Opens into nasal cavity
 Concept Review 
1.
2.
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)
3.
Where are tears formed and where do they
go?
-lacrimal gland, nasalacrimal duct
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
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
Eye Disorders 
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Myopia: Nearsightedness

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Hyperopia:
Farsightedness

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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



Clouding of lens
Macular degeneration

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Increased intraocular
pressure by aqueous humor
buildup
Cataract


Can result in complete
blindness
Glaucoma

Image focused behind
retina
Presbyopia


Focal point too near lens,
image focused in front of
retina
Common in older people,
loss in acute vision
Diabetes

Dysfunction of peripheral
circulation
The Mouth
Sense of Taste


Specific sense
organ– TASTE BUDS
Located on
projections of
tongue called
papillae
Structure of a Taste Bud
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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.*
Primary Tastes
The Nose
Sense of Smell

Olfactory organs
 Sensory
hairs
 Olfactory cells
 Olfactory nerves
 Olfactory bulb
 Olfactory tract
Smelling

Substance must be:
 Able
to become a gas
 Water soluble or very small
 Lipid soluble (to get into membrane)
Effects of Aging on the Special Senses
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Slight loss in ability to detect odors
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Decreased sense of taste
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Lenses of eyes lose flexibility

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Development of cataracts, macular
degeneration, glaucoma, diabetic retinopathy
Decline in visual acuity and color perception