The Sense Of Smell

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The Sense Of Smell
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Smelly Facts

• Taste is 75 smell
• Moths can identify a single molecule among
  others by its smell
• Dogs can distinguish non-identical
• twins by smell, but not identical ones
• A smell can trigger very strong memories
• You cannot imagine a smell
• Dogs can smell cancerous tumors in people
• Women have a keener sense of smell than men do.
• By simply smelling a piece of clothing, most
  people can tell if a woman or a man had been
  wearing it.
• Each of us has an odor that is unique, just like
  our fingerprints.
• According to some sources, the stethoscope was
  invented not to hear the heartbeat better, but to
  give doctors some distance from a patient's
  bodily odors.

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More Smelly Facts

• Much of the thrill of kissing comes from smelling
  the unique odors of another's face.
• Smells stimulate learning.  Students given
  olfactory stimulation along with a word list
  retain much more information and remember it
  longer.
• Many smells are heavier than air and can be
  smelled only at ground level.
• We smell best if we take several short sniffs,
  rather than one long one.
• Dogs have 1 million smell cells per nostril and
  their smell cells are 100 times larger than
  humans are.
• Humans use insect warning/attraction chemicals,
  called pheromones, to keep away/attract pesky
  insects.
• People who cannot smell have a condition called
  Anosmia.

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• The smells of a rose, perfume, freshly baked
  bread and cookies...these smells are all made
  possible because of your nose and brain.
• The sense of smell is called olfaction.
• All the nose parts involved in smelling are the
  olfactory apparatus.

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The Olfactory Apparatus
http//www.mhhe.com/socscience/intro/ibank/set1.ht
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Some vocabulary terms you ought to know . . .
Olfactory epithelium

• The olfactory epithelium is a specialized tissue
  inside the nasal cavity that is involved in
  smell.
• In humans, it is about the size of a postage
  stamp
• The olfactory epithelium is a patch of tissue
  covered with receptor cells that detect odor
  molecules that you breath.
• The smell equivalent of rods and cones

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• Olfactory bulb A key part of the olfactory
  apparatus, located on the under surface of the
  frontal lobe of the brain, just above the nasal
  cavity.
• Olfactory nerve sends smell signals to the
  olfactory bulb, a bulbous enlargement of the end
  of the olfactory nerve.
• Nerves then carry signals to the brain where you
  register the scent.
• We have two bulbs, so we smell in stereo!

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Frontal Lobe

• The part of each hemisphere of the brain located
  in the forehead that serves to regulate and
  mediate the higher intellectual functions.
• The frontal lobes have intricate connections to
  other areas of the brain.
• In the frontal lobes, we meld emotions,
  cognition, error detection, volition, a sense of
  self, and more to create our social brain.

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How Dose Your Olfactory Apparatus Work Together
to Create Smell?
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Odor particles drift into your nose and cause
your smell receptors to send messages to your
brain.
Olfactory Bulbs
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The smell part of the brain is in the limbic
region, and is connected to the frontal lobe
where feeling and memory are processed.
Olfactory Bulb
Olfactory epithelium
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• When you breathe in through your nose, some of
  the air passes through to your olfactory
  epithelium.  
• This tissue has millions of "receptor" cells in
  it, and each one is mounted on a microscopic hair
  that sticks out and waves in the air currents. 
• About forty of these cells must detect odor
  molecules before a smell is registered and sent
  to your brain.

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A little on TasteMolecules of food stimulate
the taste cells to send messages to your brain.
The sweet and salty buds are the least
sensitive and the bitter ones are the most
sensitive.
Taste bud
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More on Taste and Smell

• Humans basically taste four things sweet, sour,
  salt and bitter.  
• It's the odors we can smell with our noses that
  make things really taste unique! 
• For example, chocolates odors, not its taste,
  are what make it delicious. With a head cold,
  drinking hot chocolate is an entirely different
  experience. 
• In recent years a fifth taste has been
  recognized. This is umami, the protein flavor of
  monosodium glutamate. (Nature Genetics  25, 130 -
  132 (2000) doi10.1038/75952)

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Snuffy Nose

• When you have a cold and your nose is stuffed up,
  you cannot smell very well. This is because the
  molecules that carry smell cannot reach the
  olfactory receptors.

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Animals and Smell

• What do you feel when you smell male mouse
  urine?? (Depends who you are)
• http//people.bu.edu/jcherry/webpage/pheromone.htm

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Animals and Smell

• Nose size can tell you something about importance
  of smell to the organism.

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Questions You May See on a Quiz or Test . . .

• What is the evolutionary advantage to smelling
  your environment? Can you think of an example
  that relates to how Endlers Guppies survived (or
  failed to survive?)
• In order, how do the components of the
  Olfactory Apparatus detect, say, a steak
  molecule?
• (Nose, Olfactory Epithelium, Olfactory Bulb,
  Frontal Lobe.)

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Bibliography

• www.morphonix.com/.../ game/specimens/smell.html
• http//www.deodoroc.com/page7.html
• http//www.familyallergy.com/featuredarticle/blowi
  ngnose_2.jpg
• http//faculty.washington.edu/chudler/nosek.html
• http//images.meredith.com/bhg/images/01/l_mexican
  .jpg
• http//www.nysipm.cornell.edu/publications/beasts/
  skunk.gif
• http//www.tudocs.com/bread.jpg
• http//www.terleckifamily.org/Rose.jpg