Chapter 14-olfaction Flashcards Preview

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Flashcards in Chapter 14-olfaction Deck (46):
1

Odor

The translation of a chemical stimulus into a smell sensation

2

Odorant

A molecule that is defined by its physiochemical characteristics, which are capable of being translated by the nervous system into the perception of smell; physical thing you smell

3

In order to be smelled, odorants must b

Volatile, small, hydrophobic

4

Human olfactory apparatus contains

Olfactory clefts and olfactory epithelium

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Olfactory cleft

Narrow space at the back of the nose into which air flows

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Olfactory epithelium

Mucous membrane in the human nose whose primary function is to detect odorants

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Primary function of the nose

Breathe; filter, warm and humidify air that you breathe

8

Odor receptors sites are located where

On the cilia of olfactory sensory neurons where odorant molecules bind

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Odor receptors are what kind of receptors

Chemoreceptors; receptive sites bind with molecules

10

Mitral cells receive projections from how many and what type of receptors

About 200, same type of receptor; convergent, lose spatial information

11

How many different receptor types are ther

About 1000, respond to distinct chemical molecules or parts of molecules

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How many molecules are needed to activate odor receptors

7-8

13

Humans have how many receptors

6 million

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Olfactory pathway

Olfactory bulb, Piriform cortex, entorhinal cortex, limbic system, orbitofrontal

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Olfactory bulb

Olfactory info first processed here, 1 in each hemisphere that corresponds ipsilaterally to each nostril

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Primary olfactory cortex also known as

Piriform cortex

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Entorhinal cortex

Old, sensory association area, connect to the limbic system

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Limbic system

Emotion (fear) and memory, base survival learning

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Orbitofrontal cortex

Conscious perception and hedonics (liking)

20

Shape pattern theory

Dominant biochemical theory for how chemicals come to be perceived as specific odors. Contends that different scents-as a function of odorant-shape to OR shape fit-activate different arrays of olfactory receptors in the olfactory epithelium. Population coding

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Population coding

Part of shape pattern theory; the various arrays produce specific firing patterns of neurons in the olfactory bulb, which then determine the scent we perceive

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Shape of odor molecule

Physical molecule

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Pattern of odor molecule

Which scent of odor receptor and to what degree, combination processing

24

Chemical aromas

Smell odors that are not physically present; activate odor receptors, smell is an epiphenomenon (not directly representing physical world)

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How does population coding work

Odorants have different physical shapes that matter the most, and different colors (content) that also matter; receptors are selective to the shape and content of odorants

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Stereoisomers

Similar chemical compound but a different shape; result in different perceptual states-shape matters

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Odorant and receptor table: a given odorant will excite several receptors due to what

Its chemical composition

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Odorant and receptor table: a given receptor will respond to several odors, but the ___ of activity represents the composition of any given odor

Pattern

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Intensity

Certain receptors are more sensitive to aspects; can influence which receptors are active, due to relative amounts of different components of the odorant

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Because we rarely smell pure odorants, we smell mixtures; how do we process the components

Analysis and synthesis

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Analysis

Separate into parts

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Synthesis

Combine into a new whole

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Binaral rivalry

Competition between the two nostrils for odor perception; when a differen scent is presented to each nostril, we experience one scent at a time, not a combination of the two scents together

34

What we smell can affect what we

See

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Adaptation

Sense of smell is a change detector; allows for responses to new smells and/or important information

36

Bottom up receptor adaptation

Receptors stop responding to the odorant and detection stops; firing rate

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Top down influence of adaptation

Conscious thought can influence time course of adaptation

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Negative bias of smell makes it

Stronger for longer, more important

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Positive bias to a smell makes it

Decrease over time more than the neutral smell

40

Odor hedonics

The liking dimension of odor perception, typically measured with scales pertaining to an odorants perceive pleasantness, familiarity and intensity

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Familiarity of smells

We like odors that we have smelled before

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Intensity of smells

Good smells: neutral for less intense smells, unpleasant for very intense
Bad smells: dislike increases the more intense the smell gets

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Hedonic responds are most likely from nurture

Odor preferences of infants vary from adults, cross cultural data supports associative learning

44

2 aspects to support nature of hedonics

Pain response to irritating odors and variability in receptor types and amounts

45

Sniffing sticks

Pre-determined set of odorant sin distinct performance for discrimination

46

Triangle test

Participant is given 3 odors to smell, two are the same and 1 is different; identity the odd odor; used for detection and discrimination