Ms. Brandy J. Flynn, MS

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Sensation and Perception

• Chapter 3
• Ms. Brandy J. Flynn, MS

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Why study sensation and perception

• Without sensations to tell us what is outside our
  own mental world, we would live entirely in our
  own minds, separate from one another and unable
  to find food or any other basics that sustain
  life. Sensations are the minds window to the
  world that exists around us. Without perception,
  we would be unable to understand what all those
  sensations mean-perception is the process of
  interpreting the sensations we experience so that
  we act upon them.

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What is sensation

• Sensation occurs when special receptors in the
  sense organ are activated, allowing various forms
  of outside stimuli to become neural signals in
  the brain.
• The sensory receptors are specialized forms of
  neurons, the cells that make up the nervous
  system. Instead of receiving neurotransmitters
  from other cells, these receptor cells are
  stimulated by different kinds of energy(such as
  eyes being triggered by light or the vibrations
  triggered in the receptors in the ears)

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Seeing

• Light is a form of energy known as
  electromagnetic radiation. What we consider to be
  visible light is an eletromagnetic radiation that
  has a wavelength of about 400 nanometers to about
  750 nanometers.
• Sensations of light depend on the intensity and
  wavelength of light waves. Light intensity
  determines the brightness of light. Colors that
  you sense depends on wavelength

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Seeing color

• Each wavelength of light is sensed as a certain
  color. The eye rarely encounters pure light of a
  single wavelength.
• The sensation of a color result from features of
  the wavelength mixtures striking the eye. The
  three separate aspects of this sensation are hue,
  saturation, and brightness.

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Dimensions of color
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Theories of color vision

• The Trichromatic theory

• The opponent-process

• A theory of color vision stating that information
  from three types of visual elements combines to
  produce the sensation of color

• A theory of color vision stating that the visual
  elements sensitive to color are grouped into
  red-green, blue-yellow, and black-white pairs.

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Color vision (cont.)

• When Trichomatic and opponent-process theories
  are combined, it creates the complex process of
  color vision.
• We see color because we have three different
  cones that have three different sensitivities to
  different wave lengths.
• Trichomatic theory explains color vision as it
  relates to rods and cones, whereas the
  opponent-process theory explains color vision as
  it relates to the ganglion cells.

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Colorblindness

• Partially or totally unable to distinguish one or
  more chromatic colors. ( Webster Dictionary)
• Discriminate against fewer colors. Example, reds
  and greens look the same brownish gray color.
• Colorblindness is more common in men than women

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Hearing

• Sound is a repetitive fluctuation in the pressure
  of a medium such as air.
• When you speak, your vocal cords vibrate, causing
  fluctuations in air pressure that spread as sound
  waves. The waveforms are drawn in only two
  dimensions, but remember that sound waves
  actually move through the air in all directions.
• Loudness is described in units called decibels. 0
  decibels is the minimum detectable sound for
  normal hearing
• Psychological dimension of pitch depends on the
  frequency of the sound wave. Frequency is the
  number of complete waves or cycles that pass a
  given point in one second. ( A pitch is how high
  or low a tone sounds)
• Most sounds are a mixture of many frequencies and
  amplitudes, and this mixture creates a sounds
  timbre, the psychological dimension of sound
  quality. The extra waves allow you to tell the
  difference between, say, a note played on a flute
  and the same on the clarinet.

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The Ear

• The human ear converts sound energy into neural
  activity through a series of accessory structures
  and transduction mechanisms.
• The crumpled part of the ear on the side of the
  head collects sound waves in the outer ear-pinna.
  The pinna funnels sound down through ear canal.
  At the end of the ear canal, the sound waves
  reach the middle ear. There they strike the
  eardrum, a tightly stretched structure also known
  as the tympanic membrane.

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The Inner Ear

• Sound vibrations passing through the oval window
  enter the inner ear, reaching the cochlea, where
  transduction occur.
• The basilar membrane forms the floor of the tube
  that runs through the cochlea. When the sound
  wave passes through the fluid in the tube, it
  moves the basilar membrane. This movement bends
  the hair cells on the membrane. By bending the
  hair cells, this stimulates the auditory nerve,
  which sends coded signals to the brain about the
  amplitude and frequency of sound waves.

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Deafness

• The most delicate structures in the human body
  are the middle and inner ear. If damaged, it may
  cause deafness.
• Conduction deafness- deafness that is caused by
  problems with the bones of the middle ear. They
  can fuse together, preventing accurate conduction
  of vibrations from one bone to the next.
• Nerve deafness-when auditory nerves( hair cells)
  are damaged Usually caused by extreme loudness.

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Sense of smell

• The nose acts as an accessory structure that
  collects airborne odor molecules for coding and
  analysis by the olfactory system. As odor pass
  into the moist lining of the upper part of the
  nose( mucous membrane)they bind to receptors on
  the dendrites of olfactory neurons, causing a
  biochemical change.
• Pheromones-chemicals that are released by one
  creature and detected by another , shaping the
  second ones behavior or physiology. Animals
  utilze this in order to recognize the opposite
  sex. In adults, pheronomes have been shown to
  cause reproduction-related physiological changes
  in humans. Example-pheromonal signals secreted in
  womens perspiration can influence nearby womens
  menstrual cycle. Meaning, women living together
  eventually tend to menstruate around the same
  time.

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Sense of Taste

• Receptors of taste are in taste buds which are
  grouped in structures called papillae.
• The human taste system detects few basic
  sensations sweet, sour, bitter, and salty. Each
  taste bud reacts well to one or two categories
  and not so well with the other two.
• Other two sensations umami enhances other tastes
  and is produced by certain proteins. Astrigent
  produced by tannins, which are found in the tea.

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Sensing your Body

• What is the largest human organ? What is its
  function?

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Pain
Pain as an Information Sense Similar to touch and temperature. When pain occurs, nerves release chemicals that fit into the specialized receptors in pain neurons.
Emotional Aspects of Pain Our emotional response to pain depends greatly on how we think about that emotion.
Modulating Pain The Gate Control Theory Theory which suggest that there is a gate in the spinal cord that either allows pain signals to reach the brain or stops them.
Natural Analgesics Natural opiates, endorphines ( a natural pain killer)
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Perception

• The knowledge based interpretation of
  sensations.
• The constructive process by which we go beyond
  the stimuli that are presented to us and attempt
  to construct a meaningful situation.