olfaction the sense of smell. the nose knows! smell helps us: avoid dangerous situations (fumes,...
TRANSCRIPT
OlfactionOlfaction
The Sense of SmellThe Sense of Smell
The nose knows!
Smell helps us:Smell helps us:
Avoid dangerous situations (fumes, smoke) Avoid dangerous situations (fumes, smoke)
Avoid consuming poisonous substances and Avoid consuming poisonous substances and
spoiled food (sour milk) spoiled food (sour milk)
Choose mates?Choose mates?
What are olfactory stimuli?What are olfactory stimuli?
Odorants (airborne molecules)Odorants (airborne molecules)
Odorants must be volatile (they give off Odorants must be volatile (they give off vapors)vapors)
More vapors are given off when an odorant More vapors are given off when an odorant is heated!! (warm soup smells better than is heated!! (warm soup smells better than cold soup)cold soup)
Odorants reach olfactory Odorants reach olfactory receptors by:receptors by:
1. Being inhaled through the nose.1. Being inhaled through the nose.
2. Through the mouth (vapors circulate up 2. Through the mouth (vapors circulate up through throat)through throat)
The receptor in your nose catches the molecules in the air .
3,000 – 10,000
The “smell” receptors send information into your brain .
Olfaction- originates in the nasal Olfaction- originates in the nasal cavitycavity
Olfactory system structuresOlfactory system structures
Olfactory Receptor NeuronsOlfactory Receptor Neurons
Carry impulses directly to the brainCarry impulses directly to the brain
Live for 5- 8 weeks & then die.Live for 5- 8 weeks & then die.
Summary: olfactory pathwaySummary: olfactory pathway Scents travel through the nose or mouth and up to Scents travel through the nose or mouth and up to
the Olfactory receptor neuronsthe Olfactory receptor neurons Olfactory receptor neurons detect odorants in Olfactory receptor neurons detect odorants in
mucosa.mucosa. Signals are sent via olfactory receptor neurons to Signals are sent via olfactory receptor neurons to
bulb structures (glomeruli).bulb structures (glomeruli). Mitral and tufted cells carry signals to Mitral and tufted cells carry signals to
orbitofrontal cortex, temporal lobe, and the limbic orbitofrontal cortex, temporal lobe, and the limbic system.system.
Olfactory PathwayOlfactory Pathwayreceptor receptor
cellscellsolfactory olfactory
bulb bulb - - recodingrecoding
amygdalaamygdala
thalamusthalamushypo-hypo-
thalamusthalamustemporal temporal
lobelobe
Which animal is most sensitive to Which animal is most sensitive to smell?smell?
Dogs 300-10,000 times more sensitive to Dogs 300-10,000 times more sensitive to smell than humanssmell than humans
Why? Humans have 10-40 million Why? Humans have 10-40 million olfactory receptor neurons, dogs have over olfactory receptor neurons, dogs have over a billion!!a billion!!
Ability to Detect Common Ability to Detect Common OdorsOdors
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90C
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Scent to be identified
coffeeleatherbubble gummustardbologna
Variations in Odor Variations in Odor SensitivitySensitivity Women have a better sense of smell Women have a better sense of smell than men.than men.
The ability to smell diminishes with The ability to smell diminishes with age. Smell acuity is greatest during age. Smell acuity is greatest during early adulthood (ages 20-40).early adulthood (ages 20-40).
People recall smells with 65% People recall smells with 65% accuracy after a year, while visual accuracy after a year, while visual recall is only about 50% after 3 recall is only about 50% after 3 months.months.
AnosmiaAnosmia: loss of : loss of sensesense of smell of smell
May be to May be to specificspecific odors or odors or allall odors. odors.
Caused by infection to nasal cavity or brain Caused by infection to nasal cavity or brain injury (frontal lobe).injury (frontal lobe).
About 2 million people in US are anosmic.About 2 million people in US are anosmic.
Olfaction and behaviorOlfaction and behavior
Babies enthusiastically “orient” to pleasant Babies enthusiastically “orient” to pleasant odors (banana, vanilla) and cry/grimace to odors (banana, vanilla) and cry/grimace to unpleasant odors (shrimp; rotten eggs).unpleasant odors (shrimp; rotten eggs).
Babies can discriminate their mother’s scent Babies can discriminate their mother’s scent from other women (Macfarlane, 1975).from other women (Macfarlane, 1975).
EmotionEmotion
The perception of smell includes not only the odors themselves, but The perception of smell includes not only the odors themselves, but also the experiences and emotions associated with them. also the experiences and emotions associated with them.
Our Olfactory receptors are directly connected to the limbic Our Olfactory receptors are directly connected to the limbic system- the “seat” of emotion. system- the “seat” of emotion.
Most universally-rated “pleasant” odorant is Most universally-rated “pleasant” odorant is vanilla.vanilla.
Interestingly, differences in brain neurons Interestingly, differences in brain neurons activity in the left and right hemispheres have a activity in the left and right hemispheres have a relationship to the “pleasantness” of odors. relationship to the “pleasantness” of odors. Studies claim that positive emotions are Studies claim that positive emotions are predominately processed by the left predominately processed by the left hemisphere, and negative emotions in the right hemisphere, and negative emotions in the right hemisphere.hemisphere.
Scents can affect our mood- Casinos pump Scents can affect our mood- Casinos pump “pleasant” scents into the gambling floor to “pleasant” scents into the gambling floor to promote spending!!!!!promote spending!!!!!
Emotion & AttractionEmotion & Attraction
Contrary to popular belief, women are NOT attracted to the natural body odor of male sweat! Pheromones are scents that our bodies produce naturally and do increase the attraction of males to females and females to males, However, sweat is not considered a “pleasant” odor.
