The Senses

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The Senses

• Chapter Five

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The Senses

• Vision
• Hearing
• Taste
• Smell
• Touch
• Skin senses
• Vestibular
• Kinesthetic

• Each sense organ receives some sort of external
  stimulus such as light, sound waves, or pressure
• Then, it changes the sensation into a
  chemical-electrical message transmitted by the
  nervous system

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II. Vision
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The Stroop Effect
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A. The Eye

• 1. Most studied of all senses
• 2. Pupil- the opening in the iris that regulates
  the amount of light entering the eye
• a. Where the light enters the eye
• 3. Lens- a flexible, elastic, transparent
  structure in the eye that changes its shape to
  focus light on the retina

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A. The Eye (cont.)

• 4. Retina- the innermost coating of the back of
  the eye, containing the light-sensitive receptor
  cells
• a. Rods cones are responsible for changing
  light energy into neuronal impulses
• 5. Optic nerve- the nerve that carries impulses
  from the retina to the occipital lobe of the brain

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B. Cones and Rods

• 1. Cones require more light than rods before they
  begin to respond
• a. Work best in daylight
• b. Similar to color film
• 2. Rods can work in much lower light
• a. Basis for night vision
• b. Similar to sensitive black and white film

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C. Light

• Is a form of electromagnetic radiation
• 2. Other forms of electromagnetic radiation
  include
• a. Radio waves
• b. Microwaves
• c. Infrared radiation
• d. Ultraviolet rays
• e. X-rays
• f. Gamma rays

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The Electromagnetic Spectrum
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C. Light (cont.)

• 3. Visible light only makes up a small portion of
  the electromagnetic spectrum
• 4. Passing sunlight through a spectrum breaks the
  light into a rainbow of colors, each color having
  a different wavelength
• a. Objects color depends on the light that
  reaches our eyes
• b. Example- A pea looks green because it reflects
  green light and absorbs other colors

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D. Process of Vision

• Light energy stimulates the eye
• Light rays enter the eye through the cornea
• Then enter the pupil
• Light then passes through the pupil to the lens,
  which changes its shape to focus or reflect the
  light rays onto the retina
• As light rays hit the receptors, the process of
  conversion (energy is converted into a neural
  impulse) begins

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D. Process of Vision

• 3. When converted, the info is sent to the brain
  for further processing interpretation to the
  optic nerve
• 4. The ultimate processing of visual information
  occurs in the visual cortex of the brain
• Specialized cells process visual information
  including feature detectors cells activated by
  info such as slanted lines, specific shapes,
  movement, etc.

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E. Color Vision

• Young-Helmholtz (Trichromatic) theory
  (functioning of cones)
• 3 types of cones exist in the eye yellow/red,
  blue/violet, green
• Explains colorblindness
• 2. Opponent-process theory (functioning of cells
  that process info from receptors)
• 3 types of cones red/green, blue/yellow,
  black/white
• Explains afterimages (individual looks at a
  stimulus for a period of time, then shifts gaze
  away from stimulus, only to see an afterimage of
  that stimulus in a different color)

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Color Deficiency True or False?

• 1. If a persons cones dont function correctly,
  the person is color-deficient
• 2. Fewer people have trouble between red and
  green than yellow and blue
• 3. A few can only see the world in blacks,
  whites, and shades of gray
• 4. 8 of American men and 1 of American women
  are color blind/color deficient

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Color Blindness Test

• This figure tests for green colorblindness.
• They might see part of the number.
• They might not see the number at all.

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Afterimages Test
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F. Binocular Fusion

• 1. Our visual system receives two images because
  we have two eyes
• 2. Instead of seeing double, we see a combination
  of the two images
• Large retinal disparity means object is nearby
• b. Small retinal disparity means object is distant

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Retinal Disparity

• 1. Each eye projects a slightly different image
  on the retina
• 2. Example- Bring an object such as an eraser
  close to your eyes. Without moving it, look at
  the eraser first with one eye and then with the
  other. You will see a difference in the two
  images because of the different viewpoint each
  eye has.

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Vision in the Brain
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G. Nearsightedness and Farsightedness

• 1. Perfectly shaped eyeball means you have nearly
  perfect vision
• 2. Long eyeball usually means you are nearsighted
• a. You can see objects close to you, but objects
  in the distance are blurry
• 3. Short eyeball usually means you are farsighted
• a. You can see distant objects clear, but
  up-close objects are blurry

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Problems with Vision

• Here the eyeball is shaped like a football.
• The image is projected in front of the retina.
• If you pull the object closer to you, you can see
  it clearly.

• Here the eyeball is shaped like an egg on its
  side.
• The image is projected behind the retina.
• If you pull the image farther away from you, you
  can see it clearly.

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Important Figures in Vision Research

• In one experiment, done in 1959, Hubel Wiesel
• inserted a microelectrode into the primary visual
• cortex of an anesthetized cat. They then
  projected
• patterns of light and dark on a screen in front
  of
• the cat. They found that some neurons fired
  rapidly
• when presented with lines at one angle, while
• others responded best to another angle. These
• studies showed how the visual system constructs
• complex representations of visual information
  from
• simple stimulus features.

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Lasik Surgery
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• More than one million patients undergo the LASIC
• procedure in the United States each year. The
  U.S. Food
• and Drug Administration (FDA) reports that LASIK
  eye
• surgery complications occur in 1 to 5 percent of
  cases.
• According to the FDAs LASIC surgery statistics
• Glare and sensitivity to light affect 1.7 percent
  of LASIC patients.
• Visual fluctuations occur in 2.6 percent of LASIK
  patients.
• Halos around light sources are experienced by 3.5
  percent of patients.
• About 3 percent of patients report vision worse
  than before LASIC.