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The Human Ear
Auditory Sensation and Perception
• The World of the Deaf
• Artificial Senses - Hearing
PINNA
• Also called the auricle. The visible part of the outer ear. It collects sound and directs it into the outer ear canal.
EXTERNAL AUDITORY CANAL
•The tube through which sound travels to the eardrum.
EARDRUM
•Also called the tympanic membrane. A thin membrane that vibrates when sound waves reach it.
MALLEUS/INCUS/STAPESHAMMER/ANVIL/STIRRUP
•The three bones of the middle ear that carry sound vibrations from the eardrum to the chochlea.
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.
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.
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).
VESTIBULAR COCHLEAR NERVE
•Carries electro-chemical signals from the inner ear (the cochlea) to the brain.
HEARING/AUDITION
• The brain’s ability to receive sound waves from the outside world
• Sound waves are the rhythmic vibrations of air molecules
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
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
TIMBRE
• The distinctive quality of individual sounds.
• Created by an infinite combination of high and low frequencies (pitch), and high and low amplitudes (loudness).
Taste
• 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.
• 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.
• 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.
• 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.
• 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.
• 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?).
• 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.
• 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.
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 Cap’n Crunch over the generic store brand? Why or why not?
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?
Let’s 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?
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.
• 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.
Smell
Smell
Smell
Touch
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
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
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.
