Senses Notes
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Transcript Senses Notes
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
Inner Ear
Labyrinth
Bony
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)
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
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
Myopia: Nearsightedness
Hyperopia:
Farsightedness
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
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
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
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