04/03/2008 10:04:00
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Types of Receptors
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Mechanoreceptors
touch, pressure, hearing
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Thermoreceptors
temperature
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Photoreceptors
light (vision)
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Chemoreceptors
activated by chemicals for smell and taste
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Pain Receptors
physical or chemical trauma to tissue
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Referred Pain
feeling pain of internal organs in distant location (nerves
combine at spinal cord)
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The Eye
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Photoreceptors change light to chemical signal transmitted to the brain
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Light goes from the lens to the retina (photoreceptors); the lens focuses light
on the retina; the retina transforms the light to a chemical signals
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Fovea
a high concentration of photoreceptors, which allows us to see
details
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Optic Nerve
transfers chemical signal to occipital lobe
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Vitreous humor
behind the lens in front of the retina (never replaced)
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Aqueous humor
in front of lens replaced constantly; nourishment (is
replaced)
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The Ear
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Pinna
outer ear; funnel sound into auditory canal
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Eardrum
tympanic membrane; vibrates in response to sound
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Malleus }
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Incus } vibrate (amplify vibrations)
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Stapes }
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Cochlea
vibrated by ear bones through the oval window
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Hair cells move to activate sensory neurons
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Vestibular Apparatus
correct head position relative to the rest of the body
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Special Senses
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Smell
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Vision
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Hearing
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General Senses
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Touch
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Pressure
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Internal Senses
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Eye Disorders
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Glaucoma
drainage of aqueous humor blocked (increase of fluid = an
increase in pressure)
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Cataracts
“cloudiness” of the lens; light cannot penetrate
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Macular Degeneration
decrease in photoreceptors (in fovea) results in a
progressive loss of vision (can tell there is a face, but cannot point out certain
features [nose, mouth, eyes, etc.])
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Nearsightedness
loss of vision far away (light is focused in front of retina)
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Farsightedness
loss of vision close to you (light is focused behind retina)
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Ear Disorders
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Conductive Hearing Loss
blockage in sound movement
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Causes:
Wax
Infections

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