Sensation; Module 5

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• Sensation Module 5

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EYE VISION

• Structure and function
• eyes perform two separate processes
• first gather and focus light into precise area
  in the back of eye
• second area absorbs and transforms light waves
  into electrical impulses
• process called transduction

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EYE VISION

• Structure and function
• Vision 7 Concepts To Know
• Cornea
• Iris/Pupil
• Lens
• Retina/Macula/Fovea
• Optic Nerve
• Function of Light Waves
• Image Reversed

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EYE VISION

• Retina
• located at the very back of the eyeball, is a
  thin film that contains cells that are extremely
  sensitive to light
• light sensitive cells, called photoreceptors,
  begin the process of transduction by absorbing
  light waves

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p96 RETINA
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Color Vision

• There are three types of specialized cones in our
  retinas that allow us to see light.
• Red equals long light rays 500-700nm
• 2. Green equals medium light rays 450-630 nm
• 3. Blue equals short light rays 400-500nm

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Color Vision

• When a person is born without one of these cone
  types they are then color-blind to those specific
  colors.
• 1. Monochromat Total color blindness
• 2. Dichromat Missing one cone type. Usually
  trouble telling reds from greens.
• Very common in men very seldom seen in women

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EYE VISION

• Visual pathways eye to brain
• Optic nerve
• nerve impulses flow through the optic nerve as it
  exits from the back of the eye
• the exit point is the blind spot
• 2. the optic nerves partially cross and pass
  through the thalamus
• 3. the thalamus relays impulses to the back of
  the occipital lobe in the right and left
  hemisphere

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EYE VISION

• Visual pathways eye to brain
• 4. Primary visual cortex
• the backs of the occipitals lobes is where
  primary visual cortex transforms nerve impulses
  into simple visual sensations
• 5. Visual association areas
• the primary visual cortex sends simple visual
  sensations to neighboring association areas

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Structures of the ear are categorized into (3)
areas 1.Outer Ear 2.Middle Ear 3. Inner Ear
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EAR AUDITION

• We Hear
• Sound waves
• stimuli for hearing (audition)
• ripples of different sizes
• Sound waves travel through space with varying
  heights and frequency.
• Height
• distance from the bottom to the top of a sound
  wave
• called amplitude
• Amplitude How loud something is to us
• Small amplitude whisper
• Large amplitude yell

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Frequency/How close sound waves are to one another
Wavelength/How Big or Small
Speed/How fast they travel
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What Is Sound?
Any sound that you hear as a tone is made of
regular, evenly spaced waves of air molecules.
The most noticeable difference between various
tonal sounds is that some sound higher or lower
than others. These differences in the pitch of
the sound are caused by different spacing in the
waves the closer together the waves are, the
higher the tone sounds. The spacing of the waves
- the distance from the high point of one wave to
the next one - is the wavelength. All sound
waves are travelling at about the same speed -
the speed of sound. So waves with a longer
wavelength don't arrive (at your ear, for
example) as often (frequently) as the shorter
waves. This aspect of a sound - how often a wave
peak goes by, is called frequency by scientists
and engineers. They measure it in hertz, which is
how many wave peaks go by in one second. People
can hear sounds that range from about 20 to about
17,000 hertz.
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What Is Sound?
Wavelength, Frequency, and Pitch
                                                                                                                                                                                    
Figure 1 Since the sounds are travelling at
about the same speed, the one with the shorter
wavelength will go by more frequently it has a
higher frequency, or pitch. In other words, it
sounds higher.
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EAR AUDITION

• Measuring sound waves
• decibel unit to measure loudness
• threshold for hearing
• 0 decibels (no sound)
• 140 decibels (pain and permanent hearing loss

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p101 DECIBEL CHART
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p102 EAR DIAGRAM
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EAR AUDITION

• Outer, middle, and inner ear
• Middle ear
• bony cavity sealed at each end by membranes
• -the membranes are connected by three tiny bones
  called ossicles
• 1.)hammer 2.)anvil 3.)stirrup
• hammer is attached to the back of the tympanic
  membrane
• anvil receives vibrations from the hammer
• stirrup makes the connection to the oval window
  (end membrane)

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EAR AUDITION

• Outer, middle, and inner ear
• Inner ear
• contains two structures sealed by bone
• cochlea involved in hearing
• vestibular system involved in balanceCochlea
• bony coiled exterior that resembles a snails
  shell
• contains receptors for hearing
• function is transduction which (once again!) is
  the transformation of vibrations into nerve
  impulses that are sent to the brain for
  processing into auditory information

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EAR AUDITION

• Auditory brain areas
• there is a two step process occurs after the
  nerve impulses reach the brain
• 1. primary auditory cortex which is at top edge
  of temporal lobe
• transforms nerve impulses into basic auditory
  sensations
• 2. auditory association area
• combines meaningless auditory sensations into
  perceptions, which are meaningful melodies,
  songs, words, or sentences

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VESTIBULAR SENSE BALANCE

• Position and balance
• vestibular system is located above the cochlea in
  the inner ear in which are the semicircular
  canals
• each semicircular canal is filled with fluid that
  moves in response to movements of your head
• These (3) canals have hair cells that respond to
  the fluid movement
• function of vestibular system include sensing the
  position of the head, keeping the head upright,
  and maintaining balance

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Smell
Taste
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CHEMICAL SENSES

• Taste
• is a chemical sense because the stimuli are
  various chemicals
• organ tongue
• surface of the tongue contains
• taste buds

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CHEMICAL SENSES (CONT.)

• Tongue
• Six basic tastes
• sweet
• salty
• sour
• bitter
• umami meaty-cheesy taste
• fat
• ________________________________
• 7. Menthol?

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CHEMICAL SENSES (CONT.)

• Surface of the tongue
• chemicals, which are the stimuli for taste, break
  down into molecules
• molecules mix with saliva an run into narrow
  trenches on the surface of the tongue
• molecules then stimulate the taste buds

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mami/index.html
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CHEMICAL SENSES (CONT.)

• Taste buds
• shaped like miniature onions
• are the receptors for taste
• here the chemicals dissolved in saliva activate
  taste buds..
• which then produces nerve impulses that reach
  areas of the brains parietal lobe
• then the brain transforms impulses into
  sensations of taste

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CHEMICAL SENSES (CONT.)

• Smell, or olfaction
• Olfaction
• called a chemical sense because its stimuli are
  various chemicals that are carried by the air
• Our smelling function is carried out by two small
  odor-detecting patches made up of about five or
  six million yellowish cells high up in the
  nasal passages.

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• The human nose can detect (approx.) 10,000
  smells.
• The human nose (not as sensitive as a hound dog)
  can detect a smell that is 1 part chemical per
  billion parts of air molecules

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CHEMICAL SENSES (CONT.)

• Smell / Olfaction
• Stimulus
• we smell volatile substances
• these volatile substances are released molecules
  in the the air at room temperature
• example
• a skunks spray, warm brownies perfumes/colognes
  of lovers, gasoline, dog poo, I think you get it!

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CHEMICAL SENSES (FYIs)

• Sensations and memories
• nerve impulses travel to the olfactory bulb
• where we can identify as many as 10,000
  different odors
• Why do we stop smelling our own deodorants or
  perfumes? Because of decreased responding!
• Its called Adaptation

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CHEMICAL SENSES (CONT.)

• Functions of olfaction
• one function to intensify the taste of food
• second function to warn of potentially dangerous
  foods
• third function elicit strong memories emotional
  feelings

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TOUCH

• Our sense of touch is controlled by a huge
  network of nerve endings and touch receptors in
  the skin known as the somatosensory system.
• This system is responsible for all the sensations
  we feel - cold, hot, smooth, rough, pressure,
  tickle, itch, pain, vibrations, and more. Within
  the somatosensory system, there are four main
  types of receptors mechanoreceptors,
  thermoreceptors, pain receptors, and
  proprioceptors.

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TOUCH

• Receptors in the skin
• 1. Mechanoreceptors
• 2. Thermoreceptors
• 3. Pain receptors
• 4. Proprioceptors
• 5. Hair follicles

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TOUCH

• Skin
• the outermost layer
• is a thin film of dead cells containing no
  receptors
• just below, are the first receptors which look
  like groups of threadlike extensions
• next the middle and fatty layer
• encompass a variety of receptors with different
  shapes and functions

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TOUCH

• 1. Mechanoreceptors These receptors perceive
  sensations such as pressure, vibrations, and
  texture. There are four known types of
  mechanoreceptors whose only function is to
  perceive indentions and vibrations of the skin
  Merkel's disks, Meissner's corpuscles, Ruffini's
  corpuscles, and Pacinian corpuscles.
• are in the fatty layer of skin
• are the largest touch sensor
• are also highly sensitive vibration
• 2. Thermoreceptors As their name suggests, these
  receptors perceive sensations related to the
  temperature of objects the skin feels. They are
  found in the dermis layer of the skin. There are
  two basic categories of thermoreceptors hot and
  cold receptors.
• Hot receptors start to perceive hot sensations
  when the surface of the skin rises above 86 º F
  and are most stimulated at 113 º F. But beyond
  113 º F, pain receptors take over to avoid damage
  being done to the skin and underlying tissues.
• Cold receptors start to perceive cold sensations
  when the surface of the skin drops below 95 º F.
  They are most stimulated when the surface of the
  skin is at 77 º F and are no longer stimulated
  when the surface of the skin drops below 41 º F.
  This is why your feet or hands start to go numb
  when they are submerged in icy water for a long
  period of time.

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TOUCH

• 3. Pain receptors These receptors detect pain or
  stimuli that can or does cause damage to the skin
  and other tissues of the body. There are over
  three million pain receptors throughout the body,
  found in skin, muscles, bones, blood vessels, and
  some organs. They can detect pain that is caused
  by mechanical stimuli (cut or scrape), thermal
  stimuli (burn), or chemical stimuli (poison from
  an insect sting).
• 4. Proprioceptors these receptors sense the
  position of the different parts of the body in
  relation to each other and the surrounding
  environment. Proprioceptors are found in tendons,
  muscles, and joint capsules. This location in the
  body allows these special cells to detect changes
  in muscle length and muscle tension. Without
  proprioceptors, we would not be able to do
  fundamental things such as feeding or clothing
  ourselves.

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TOUCH

• 5. Hair receptors
• free nerve endings wrapped around the base of
  each hair follicle
• these hair follicles fire with a burst of
  activity when first bent and give a sense of
  light touch.
• If the hair remains bent for a period of time,
  the receptors will cease firing.
• .. Sensory adaptation. example wearing a
  watch, wearing a shirt with a collar etc.

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TOUCH

• Brain areas (that translate nerve firings into
  sensation)
• somatosensory cortex located in the parietal
  lobe transforms nerve impulses into sensations
  of touch temperature, and pain

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PAIN

• What causes pain?
• pain is the complex mixture of sensation and
  perception that is in part mediated by emotion
  it may result from physical damage, ones
  thoughts, or environmental stressors
• therefore pain results from many different
  stimuli, most of which are subjective in nature

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Gate-Control Theory

• When we are occupied with other physical/mental
  activities we often feel less or no pain at all.
• -such as when you stub a toe, then you rub it
• or.
• -when you nearly sever a finger with a power
  tool and pound your fist into a wall only to
  sense that your finger doesnt feel so bad
  anymore

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Gate-Control Theory

• .On a serious note nearly five years ago now.
• For example A NYC cop was shot through the
  heart he didnt realize until the situation was
  over b/c he was physically/mentally absorbed in
  something.

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PAIN

• Perhaps your thinking How does the mind stop
  pain? (according to the Gate Theory)
• well
• non-painful nerve impulses compete with pain
  impulses in trying to reach the brain
• they create a bottleneck or neutral gate
• soshifting attention or rubbing an injured area
  decreases the passage of painful impulses
• result Pain is dulled!

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PAIN (Biologically)

• What does the body do to help us cope? Endorphins
• neurotransmitters secreted in response to injury
  or severe physical or psychological stress
• the
• pain reducing properties of endorphins are
  similar to those of morphine so our..
• brain produces endorphins in situations that
  evoke great fear, anxiety, stress or bodily
  injury as well as intense aerobic activity.