Transcript SMELL & TASTE

Olefaction
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Smell
• Chemical detection without the danger of
ingesting poison
• Object identification
• Sexual signaling
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Nasal Anatomy
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Nasal Anatomy
• Nasal cavity - Hollow portion of head behind nose warms air, filters out dust, houses the sense of smell
• Olfactory epithelium - Area of nasal cavity with
olfactory receptors
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Nasal Anatomy
• Receptors are genuine neurons (unlike photoreceptors and
hair cells)
• Unlike other neurons, receptors are continually regenerated
• 1,000 different receptor types - about 1% of your DNA
codes for olfactory receptors making it the largest single
gene family
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Olfactory
Epithelium
• Receptors have
four parts cilia,
olfactory knob,
olfactory rod
and the axon
• Olfactory nerve - the axons of the
olfactory receptors form bands
which travel to the olfactory bulb
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Olfactory Bulb
• Olfactory bulb - organ which houses all the nerves which
receive inputs from the olfactory receptors
(mitral cells and periglomerular cells)
• Limbic
and
Thalamic
connections
• Olfactory
cortex
(frontal
lobe)
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Early Olfactory
Pathway
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Central
Olfactory
Pathways
Olefactory Cortex
Limbic
System
Thalamus
Olfactory Bulb
Olfactory Receptors
Odorant
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Central
Olfactory
Pathways
Olefactory Cortex
Limbic
System
Thalamus
Olfactory Bulb
Olfactory Receptors
Odorant
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Central
Olefactory
Pathways
Olefactory Cortex
Limbic
System
Thalamus
Olfactory Bulb
Olfactory Receptors
Odorant
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Central
Olefactory
Pathways
Olefactory Cortex
Limbic
System
Thalamus
Olfactory Bulb
Olfactory Receptors
Odorant
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Central
Olefactory
Pathways
Olefactory Cortex
Limbic
System
Thalamus
Olfactory Bulb
Olfactory Receptors
Odorant
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Central
Olefactory
Pathways
Olefactory Cortex
Limbic
System
Thalamus
Olfactory Bulb
Olfactory Receptors
Odorant
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Perception of Smell
• The dimensions of smell
Foul
Flowery
Fruity
Burnt
Resinous
Spicy
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Perception of Smell (cont.)
• We can distinguish between about 10,000 different
smells
Different threshold levels for different smells
• Two thresholds for each smell -low threshold for
the existence of a chemical, somewhat higher
threshold to discriminate one smell from another
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Perception of Smell (cont.)
• Adaptation - Olfactory fatigue - cross-adaptation
• Smell Constancy - receptors are more stimulated
during a deep sniff than a shallow one - the
judgment of odor intensity does not change -
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Perception of Smell (cont.)
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Pheromones: Mammals
Powerful effects on behavior, specifically
sexual behavior, territorial behavior and
identification of kin
Mammals
• Most mammals only become sexually aroused in
the presence of pheromones
• Increased likelihood of pregnancy
• Synchronization of estrus cycles
• Mutual recognition of mother and offspring
• Territory marking (e.g. dogs)
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Pheromones: Mammals
• Releasers - trigger a specific behavioral response
• Primers - trigger a hormone response which increases
the likelihood of certain types of behaviors
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Pheromones: Humans
Humans
• infants can correctly identify their own mother's
milk and are much more likely to nurse when its
their own mother
• female menstrual cycles can be altered by
pheromones - the sorority effect
• male and female behavior is highly influenced by
pheromones
t-shirt experiment - musky versus sweet • the musky odor is rated by males and females as
unpleasant and is thought to serve as a territorial
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marker among males
Pheromones: Alpha Androstenol
alpha androstenol (predominantly secreted by females)
1. Increase sexual arousal in males
2.
Increases male perception of female attractiveness
•
women in photographs were rated as significantly more sexually
attractive when judges were first exposed to alpha androstenol
3.
Increases willingness of females to initiate social contact with
males
•
females exposed to alpha androstenol were much more receptive to
male-initiated contact
•
more likely to seek out male company
•
less likely to seek female company
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