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Smell (March 10, 2000, Two)

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Program Summary

Take a deep breath. Smell anything? Maybe you're getting a few whiffs of early-spring air. Maybe you're dealing with the garlic-anchovy pizza on your co-worker's desk. Or maybe you're catching molecules of perfume from the woman next to you in the elevator. So how does the sense of smell work? What happens when it doesn't work right? And how are efforts to develop odor-related technology progressing?

On one level, the workings of your sniffer are pretty straightforward. Odor molecules have a specific shape. When they enter the nose, if those shapes match up with surface proteins on odor-sensing neurons (about 10 million of them, with over 1,000 configurations) the neuron fires. But at levels beyond that, it gets much more complicated, involving subtle mixes of chemicals, the ways that proteins bind together, how long they stick to receptors, genetics, and more.

"Not smelling" may seem like a joke, but 2–3 percent of the population is "anosmic"—having little or no sense of smell. About 15 percent of the population has some form of "odor blindness"—not being able to smell certain things that other people can smell. And since about 90 percent of what people perceive as "taste" is actually produced by smell (hold your nose and eat a piece of chocolate—it doesn't taste very chocolatey at all!) a lack of ability to smell can become a real quality-of-life issue.

Several companies are developing "artificial noses," sensors that can identify odor components on the fly. Most of these are designed for some type of quality-control monitoring or environmental sampling, such as making sure that fish shipments are fresh or that oil refineries aren't emitting compounds they shouldn't. A few inventors are working on using an artificial nose for medical diagnoses, using it to sense faint tell-tale scents given off by certain bacteria, for example. And there's even an effort afoot to create a sort of Smell-o-Vision for the Internet Age—an artificial odor generator called DigiScents.

Guests

Alan Hirsch, M.D., neurological director of the Smell and Taste Treatment and Research Foundation in Chicago

Stuart Firestein, associate professor of biology at Columbia University in New York

Nathan Lewis, professor of chemistry at the California Institute of Technology in
Pasadena, California

Related Links and Resources

Related Links and Resources

Howard Hughes Medical Institute: Seeing, Hearing and Smelling the World
Monell Chemical Senses Center
National Institute of Deafness and other Communication Disorders: Smell and Taste
National Institutes of Health MEDLINEplus: Taste and Smell Disorders
Neuroscience for Kids: The Senses
Newton's Apple Teacher's Guide to Taste And Smell
Wired.com, July 11, 1999: “You've Got Smell!”

For Discussion:

• How does the brain receive smell messages?
• How do we use our sense of smell?
• The senses of smell and taste work together. The last time you had a cold, how did it affect your ability to smell? Was your appetite affected, too?
• Smells often trigger memories. Has this happened to you?
• Do you think gender makes a difference in the ability to detect odors?
• Why do animals have a better sense of smell than humans?
• Would you like to be able to smell as well as a dog, or are there smells you’d rather not know about?

Activities

So nosy! The teacher resource page at Neuroscience for Kids’ Our Chemical Senses: Olfaction has an excellent overview and lesson plan for the smell and taste systems. One experiment explores olfactory fatigue; “Try Your Own Experiment” helps students devise their own smell experiments. The Nose Knows at the same site briefly explains the olfactory system to kids and why smells can trigger memories. A diagram and fun facts spice things up. Students can test their smell ability with experiments on the Expose Your Nose page and test their knowledge with the Nose and Olfaction Review. Visit Innerbody.com for an animation of air entering the nasal passages.

Smell-ow yellow. Newton's Apple Teacher's Guide to Taste And Smell is another wonderful lesson plan with interesting discussion questions, vocabulary, and experiments. Students will enjoy the jelly bean “taste guess.” Another fun experiment asks students to sniff various things and write stories about the resulting memories.

Everybody “nose” what’s going on. What's That Smell? The Nose Knows at KidsHealth.org provides details on the connection between smell and taste and how smell acts as an early warning system. Have students explore the smell-taste link by tasting foods with and without holding their noses. Even more activities can be found at the Franklin Institute’s November 1997 Minutes from ME: Smelling.

The bionic nose. NASA’s Spaceplace: Let's Get Nosy! Discusses the development of the “e-nose,” an electronic sniffer developed for use on spacecraft to detect dangerous gas leaks.

Smell like a dog. Because animals must hunt for their food and avoid becoming prey, most animals’ sense of smell is far better than a human’s. Sniff around the Dogs exhibit at the Natural History Museum of Los Angeles, then trot on over to Amazing Animal Senses at Neuroscience for Kids and The Nose Knows at the San Diego Zoo’s Teachers’ Lounge for tons of fascinating facts about animal senses. The Zoo page also has a terrific activity that turns students into search dogs (this page is geared toward grades k-3, but students of all ages will enjoy the scent search.)

Helping hounds. ThinkQuest’s C.L.A.W.s To The Rescue is a heartwarming tribute to animals that have been trained to aid humans, from search-and-rescue dogs to monkey assistants for the disabled. Invite the local police K-9 unit to do a demonstration for the class.

Use the search box below to perform a Google search within any of the specifc sites or general domains mentioned in this Activities section.

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