The Human Ear

1
The Human Ear

• Auditory Sensation and Perception

2

• How Do We Hear?

3

• The World of the Deaf
• Artificial Senses - Hearing

4
(No Transcript)
5
(No Transcript)
6
PINNA

• Also called the auricle. The visible part of the
  outer ear. It collects sound and directs it into
  the outer ear canal.

7
(No Transcript)
8
EXTERNAL AUDITORY CANAL

• The tube through which sound travels to the
  eardrum.

9
(No Transcript)
10
EARDRUM

• Also called the tympanic membrane. A thin
  membrane that vibrates when sound waves reach it.

11
(No Transcript)
12
MALLEUS/INCUS/STAPESHAMMER/ANVIL/STIRRUP

• The three bones of the middle ear that carry
  sound vibrations from the eardrum to the chochlea.

13
(No Transcript)
14
(No Transcript)
15
EUSTACHIAN TUBE

• A tube that connects the middle ear to the back
  of the nose it equalizes the pressure between
  the middle ear and the air outside and allows the
  bones of the middle ear to vibrate properly.
  When you "pop" your ears as you change altitude
  (going up a mountain or in an airplane), you are
  equalizing the air pressure in your middle ear.

16
(No Transcript)
17
SEMICIRCLE CANALS

• Three loops of fluid-filled tubes that are
  attached to the cochlea in the inner ear. They
  help us maintain our sense of balance.

18
(No Transcript)
19
COCHLEA

• A spiral-shaped, fluid-filled inner ear
  structure it is lined with cilia (tiny hairs)
  that move when vibrated and cause an electrical
  nerve impulse to form (transduction).

20
(No Transcript)
21
(No Transcript)
22
(No Transcript)
23
VESTIBULAR COCHLEAR NERVE

• Carries electro-chemical signals from the inner
  ear (the cochlea) to the brain.

24
(No Transcript)
25
HEARING/AUDITION

• The brains ability to receive sound waves from
  the outside world
• Sound waves are the rhythmic vibrations of air
  molecules

26
LOUDNESS

• The intensity/energy of a sound wave, measured in
  decibels.
• On a graph, amplitude is the height of a sound
  wave. The higher the wave, the more force it
  will hit the eardrum with, and the resulting
  sound is louder. The lower the wave, the less
  force it will hit the eardrum with, and the
  resulting sound is softer.
• Min 0 decibels Max 120 decibels

27
(No Transcript)
28
PITCH

• Pitch is the property of sound that we perceive
  as higher and lower tones. Changes in pitch are
  caused by differences in the frequency at which a
  sound wave vibrates.
• On a graph, the more waves per second results in
  a higher tone, and the less waves per second
  results in a lower tone.
• Pitch is measured in Hertz (Hz) how many times
  a wave repeats per second
• Min 20 Max 20,000

29
(No Transcript)
30
TIMBRE

• The distinctive quality of individual sounds.
• Created by an infinite combination of high and
  low frequencies (pitch), and high and low
  amplitudes (loudness).

31
(No Transcript)
32
Taste
33

• How Does Taste Work?

34

• Taste is the sense in humans and other animals by
  which five qualities of a food substance are
  distinguished (sweetness, sourness, saltiness,
  bitterness, and umami).
• All food tastes are a result of their unique
  combination of these five basic qualities.

35

• Bitter taste is perceived by many to be
  unpleasant, sharp, or disagreeable. Common bitter
  foods and beverages include coffee, unsweetened
  chocolate, bitter melon, beer, olives, and citrus
  peel.
• Saltiness is a taste produced primarily by the
  presence of sodium ions.
• Sourness is the taste that detects acidity.

36

• Sweetness is produced by the presence of sugars,
  some proteins and a few other substances.
• Umami is the name for the taste sensation
  produced by compounds such as glutamate, found in
  beef, lamb, parmesan and cheese, as well as soy
  sauce.

37

• The mucous membrane lining of the tongue is
  covered with tiny projections of papillae, each
  of which houses 200 to 300 taste buds. In humans,
  the papillae are located on the surface and sides
  of the tongue, the roof of the mouth, and the
  entrance to the pharynx.

38

• Foods are broken down by saliva. Food molecules
  are absorbed by the papillae and then into the
  taste buds.
• The unique properties of the food molecules will
  stimulate the thresholds for their respective
  taste sensors. Depending on which combination of
  sensors are activated, a different message will
  be sent to the brain to be processed.

39
(No Transcript)
40
(No Transcript)
41
(No Transcript)
42

• The somatosensory cortex will decode the
  information received (this food is a combination
  of sweet and sour).
• The hippocampus will label the food based on our
  previous experiences with that combination (that
  specific combination of sweet and sour is called
  barbecue) .
• The amygdala will add an emotional experience to
  the food (do I like that barbecue or not?).

43
(No Transcript)
44

• Very slight regional differences in sensitivity
  to compounds exist on the tongue, though these
  regional differences are subtle and do not
  conform exactly to the traditional tongue map.
  Individual taste buds, in fact, typically respond
  to compounds evoking each of the five basic
  tastes.

45
(No Transcript)
46

• Supertasters are those individuals who have
  approx. 25 more taste buds than the average
  person. About 25 of the population fit into
  this category.
• Non-tasters are those individuals who have
  approx. 25 less taste buds than the average
  person. About 25 of the population fit into
  this category.

47
Think About It

• What influences your food preferences? When you
  go to the store to purchase food, why do you
  choose one specific brand over another? Do you
  find that you always choose Capn Crunch
  over the generic store brand? Why or why
  not?

48
Is it true?

• Do name brand foods really taste better than
  their store brand competitors?
• If current research is correct, many people base
  their food purchases on the perception of better
  taste rather than actual taste. Due to
  advertising exposure, product placement, higher
  pricing, catchy slogans, etc., many people
  believe that name brands taste better. But do
  they?

49
Lets Test It !!

• In a blind taste-test, if this research is
  correct, we should be able to determine which is
  the name brand and which is the store brand
  product on taste alone as well. Can we?

50
(No Transcript)
51
Smell

• Olfactory receptors/cells in the upper nasal
  passages detect odor molecules in the air.
• The unique chemical properties of each odor
  molecule create the perceptions of smell.
• Humans can perceive approximately 10,000
  different scents.

52

• Odor molecules dissolve in the mucus membrane of
  the upper nasal passage, and their unique
  chemical properties are absorbed by cilia.
• The cilia are responsible for transducing the
  message and sending it to the olfactory bulb in
  the frontal lobe for identification.
• The hippocampus and the amygdala add context and
  emotional responses to the perception.

53
(No Transcript)
54
(No Transcript)
55
Smell
56
Smell
Smell
57
(No Transcript)
58

• Touch

59
Touch

• Touch receptors are on the skin
• Four basic skin senses are
• Pain
• warmth
• cold
• pressure
• All skin sensations are a combination of these
  four basic senses

60
(No Transcript)
61
Sensitive Parts of the Body

• Most Sensitive
• Back of knees
• Neck region
• Bend of elbow

• Least Sensitive
• Tip of the Nose
• Sole of foot
• Ball of thumb

62
(No Transcript)
63
Gate-Control Theory of Pain

• Experience of pain depends (in part) on whether
  the pain impulse gets past neurological gate in
  the spinal cord and thus reaches the brain.