The Sense Of Smell

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 has 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.

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.

• 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.

The Olfactory Apparatus

http://www.mhhe.com/socscience/intro/ibank/set1.htm

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. There is one inside each nostril.– 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 breathe in. – The smell equivalent of rods and cones

• 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.

• The olfactory epithelium sends 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!

How Dose Your Olfactory Apparatus Work Together to Create

“Smell”?

Odor particles drift into your nose and cause your smell receptors to

send messages to your brain. Olfactory Bulbs

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

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.

A little on Taste…

Molecules of food stimulate the taste cells to send messages to your brain.

There are different kinds of taste buds, some are more sensitive than others.

Taste bud

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, chocolate’s 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) doi:10.1038/75952)

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.

Questions you might see on a quiz or test….

• What is the order that smell happens? Which organs receive the molecules 1st, 2nd and 3rd?

• How does smell affect taste?

• What happens when you get a stuffy nose?

Bibliography• www.morphonix.com/.../ game/specimens/smell.html• http://www.deodoroc.com/page7.html• http://www.familyallergy.com/featuredarticle/blowingnose_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