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Survey of the Senses > Midterm 3 - Topic 12 > Flashcards

Midterm 3 - Topic 12 Flashcards

1
Q

What are smell and taste classified as? Why?

A

The chemical senses
Have receptors sensitive to chemical stimulation

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2
Q

How are smell and taste closely related to each other in another way?

A

Taste identification is not possible when the nostrils are blocked

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3
Q

What are the most mysterious of the senses?

A

Smell and taste

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4
Q

What concrete examples is smell related to?

A

Involved in impression formation
Involved in guiding out eating behaviour

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5
Q

Why does mystery surround smell?

A

Comes in part from the fact that it is difficult to classify the stimuli for smell
Unlike other senses, smell does not relate directly to thought processes –> more closely related to emotions

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6
Q

What plays the most important role in the study of smell?

A

Classification of odors

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7
Q

First example of smell stimulus creator and year

A

Proposed in 1916 by Henning

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8
Q

Henning’s 1916 smell stimulus

A

Prism shaped classification defines odors in terms of six basic smells: putrid, fragrant, spicy, resinous, burned, ethereal
Only simple odors are located on the surface of the prism, not inside
Complex odors (combinations) can be represented inside the prism

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9
Q

Problems with Henning’s 1916 smell stimulus

A

Odor judgment varies from person to person
One person’s perceptions could be inconsistent with this system, and this exception is enough to rule out the classification
The different dimensions are somewhat arbitrary and not clearly defined (not empirically based)

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10
Q

Another system for the classification of odors proposer and year

A

Amoore 1970

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11
Q

What does Amoore’s 1970 system focus on?

A

Chemical structure of odors

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12
Q

Amoore’s 1970 system for the classification of odors

A

Six primary odors are involved as a mixture in any odor:
Camphoraceous (e.g., mothballs)
Pungent (e.g., vinegar)
Floral (e.g., roses)
Ethereal (e.g., dry-cleaning fluid)
Minty (e.g., peppermint stick)
Musty (e.g., musk perfume)
Putrid (e.g., rotten egg)

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13
Q

Explain Amoore’s stereochemical theory
Give examples

A

Odorous molecules have specific shapes that determine the kind of odor we smell
Minty = oval molecules
Mothballs = round molecules

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14
Q

In Amoore’s stereochemical theory what are receptor sites related to? Explain

A

The shape of molecules
Perceived smell depends on what receptor sites are stimulated
Smells with similar molecular structures should also be similar in their perceived smell

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15
Q

Criticisms of Amoore’s stereochemical theory

A

Has not been supported by research
Molecules of similar size and shape are often perceived as different in terms of smell judgment

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16
Q

Latest work on classification of smells

A

Suggests the existence of as many as 10 primary odors and as little as 4
A satisfactory way to classify odors remains to be developed

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17
Q

Smell classification and industry

A

Different professions have different ways to classify odors

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18
Q

Where does the olfactory system originate?

A

In the nose

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19
Q

Briefly explain the anatomy of the nasal area

A

Air comes in the nasal vestibule
Enters the nasal cavity
Air spins around in the turbinate

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20
Q

Where does the air containing odors come from?

A

The nostrils and the passage that allows communication between the back of the throat and the nasal cavity

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21
Q

Role of turbinate bones
Result?

A

Forces most of the air we breathe to go down the throat
Only a small amount of the air we breathe stimulates the smell receptors at the top of the cavity

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22
Q

Olfactory epithelium

A

Area that contains the smell receptor cells

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23
Q

Olfactory epithelium size

A

About 2.5 cm^2 for each nostril

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24
Q

How many kinds of receptors does smell have?

A

One

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25
For humans, how many smell receptors does each nostril contain? How about for dogs?
5 million 100 million
26
What is the most important feature of each smell receptor?
The cilia protruding out of each cell
27
What is likely about the cilia and smell?
The action of the odorant on the receptor takes place on the cilia
28
How does smell differ from hearing and vision in terms of receptors?
Unlike other senses, there is a direct contact between the stimulus and the receptors
29
In vision, what structures block direct contact between the stimulus and the receptors?
The cornea and other structures
30
In hearing, what structures block direct contact between the stimulus and the receptors?
The eardrum
31
What also serve as receptors for smell?
Free nerve endings on the trigeminal nerve
32
What do the free nerve endings of the trigeminal nerve register? Examples?
Sensations that are important to smell and taste The feel of cigarette smoke, the bite of chili pepper, the burn of ammonia, the coolness of mint
33
What is responsible for the first processing of the signals sent by the smell receptors?
The olfactory bulb located above the receptor cells
34
What is the olfactory bulb?
The actual olfactory area in the brain
35
When is the info from the two olfactory bulbs (one for each nostril) combined?
Not until further along the olfactory pathways
36
What two pathways do the olfactory bulb's neurons follow?
One pathway goes through the thalamus, frontal cortex, and hypothalamus Another pathway goes to the amygdala
37
How does the pathway of the olfactory bulbs relate to different cognitions? Explain
Link between motivation, emotions, memory, and smell Frontal cortex (conscious perception of smell) Hypothalamus and amygdala (motivational and emotional aspects of smell) Hippocampus (odor memory)
38
Absolute threshold for smell
Concerns the smallest detectable concentration of a chemical required for an observer to report "I smell something" Amount of the chemical per litre of air
39
How does absolute threshold vary?
Depending on the substance studied
40
Do not confuse threshold with identification. Explain.
The threshold is the smallest amount of an odorant required for detection, not identification Individual differences in smell sensitivity also exist
41
What are errors in odor identification typically due to?
Problems in vocabulary rather than olfactory problems
42
Difference threshold for smell meaning
Minimum detectable difference between two stimuli
43
Difference threshold for smell
Has received little attention The rare studies where this has been examined suggest that the concentration of a substance must be increased by 20% to 30% for the difference in smell to be noticed
44
Adaptation for smell
Sensitivity decreases following the continuous presentation of an odor Essentially, when we are exposed to a specific odor, receptor response for that odor decreases very quickly
45
Specific figures for adaptation for smell
About 50% decrease in receptor response in first second Almost no smell after 1 min Only applies to faint odors
46
What is easier to classify, taste or smell stimuli?
Taste stimuli are easier to classify than smells
47
How many basic kinds of taste stimuli are there?
Most researchers agree that we taste four basic kinds of stimuli, but a fifth basic taste is still under debate
48
Four basic kinds of taste stimuli
Sweet (e.g., sugar) Bitter (e.g., lemon) Salty (e.g., salt) Sour (e.g., vinegar)
49
Fifth debated basic taste
Umami (e.g., savory --> rich in glutamate)
50
What is the basic receptor for taste stimuli?
The taste bud
51
Where are the receptors located generally? Specifically?
The receptors are located through the mouth, not only on the tongue The taste buds are located on little bumps on the tongue called papillae
52
How many different types of papillae have definitely been identified? What is unclear?
Four types Umami-linked papillae are unclear
53
Are the taste buds located on top of the tongue?
The taste buds are not on top of the tongue; they are lined up on either side of the papillae in the pits
54
Explain the mechanism of the taste bud
The tips of the receptor cells (microvilli) reach out into the pit and can touch taste molecules present in the pit (mixed with saliva) The taste stimuli interact with taste molecules in the microvilli membrane and creates an action potential
55
How many taste buds do humans have? What is their life expectancy?
Humans have about 10,000 taste buds with a life expectancy of about 10 days
56
How do taste buds renew themselves?
By a process in which cells surrounding the taste bud migrate toward the center and replace the dead cells
57
What records taste dimensions? Example?
Free nerve endings of the trigeminal nerve are found in the mouth They record taste dimensions such as spiciness
58
Different regions of the tongue are sensitive to...
Different taste qualities
59
Middle of the tongue
Does not have taste buds Thus, it is a "blind spot" for taste
60
Taste coding
Despite the location/taste link, taste coding is not based on different types of receptors, each sensitive to a specific taste dimension There are receptors sensitive to a particular taste quality. However, others are sensitive to two, three, and even all four taste qualities It appears that each taste bud responds more strongly to only one taste, even though it may respond to more than one taste quality
61
Specific type of taste coding
Across-fiber pattern coding
62
Taste code pathway to brain
Hypothalamus, amygdala, frontal cortex
63
What does the absolute threshold for taste depend on?
The substance used and on the area of the tongue that is stimulated
64
What is required for taste recognition, compared to the absolute threshold?
A larger amount of the stimulus
65
Precise threshold for taste identification
Cannot be obtained, because of the different sensitivity of various areas in the mouth
66
Difference threshold for taste
Minimum detectable difference between two stimuli
67
Specific difference threshold for taste
Has not been studied much Studies suggest that the concentration of a substance must be increased by 15% to 25% for the difference in taste to be noted
68
Why should we care about taste thresholds?
Humans often avoid ingesting substances with strong bitter or sour tastes as protection against harmful substances with a strong bitter taste The ability to identify the slight sour taste of spoiled food is also a good way to avoid food poisoning
69
Taste adaptation
When a specific substance is placed on the tongue, our threshold for that substance increases As soon as the substance is removed, the threshold rapidly goes back to normal (recovery)
70
In everyday life, why is adaptation not as rapid?
Because we rinse out out mouth as we eat by drinking liquid, we move the food all around our mouth as we chew, we pause between mouthfuls
71
Factors affecting taste and smell
Smell affects taste perception (smell-taste interaction): Intensity of the perceived flavour is due to both taste and odor intensity
72
Effect of vision on smell
For odors close to threshold, people are more likely to report an odor if the stimulus is coloured Perceived intensity of a coloured odorant is increased as compared to the same odorant with no colour, especially if the colour is consistent with the odorant
73
Effect of vision on taste
Red-coloured sugar solutions were judged sweeter to taste than uncoloured solutions Cherry-flavoured drink is more often misidentified as orange drink when it is orange coloured
74
Temperature and taste
Humans are most sensitive to tastes when food is presented at room temperature

Survey of the Senses (13 decks)

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