Making Sense: The Biology of the Senses
Spring 2008
Week 1 — Taste the Rainbow!
Objectives:
• Understand that taste perception comes from the brain not the tongue. The nerves in the
tongue send signals to the brain.
• Understand animals have structures that serve different functions for growth, survival
and reproduction. The tongue can taste dangerous substances more readily than
harmless ones.
• Understand the connection between biology and perception of taste in the brain.
Background Info (for mentors):
The tongue is covered in fungiform papillae, which are the large bumps you see on
your tongue. If you have a lot of bumps, you are a supertaster. If not, you are simply a
taster or nontaster. On the sides of each bump, there are the taste buds. Nerves attach to
taste buds to send the signal to the brain.
There are 3 different types of tasters: super tasters, tasters, and nontasters. A
supertaster is someone who can experience taste with a far greater intensity. Scientists
think this is caused by the greater number of fungiform papillae (bumps) on the tongue.
1
Making Sense: The Biology of the Senses
Spring 2008
Tasters experience taste with an average intensity. Nontasters can still taste, but they less
intense taste response than the other two categories.
Traditionally, children were taught that certain geographic regions of your tongue
that only react to a specific taste: bitter, sweet, salty, sour, and umami. Actually, you can
taste all five in all regions of your mouth, including the epiglottis and soft palate.
Nevertheless, there are different thresholds for taste sensation, which follow the map below.
As such, sensations for bitterness are strongest in the back of the tongue.
There are actually five tastes that the tongue can sense. The
lesser known of the five is umami, which best described as
meaty or savory.
We can sense more than the five primary tastes, such as
astringency, pungency, and metallic tastes. This sensation
comes from the combination of taste receptors and smell
receptors to create the perception of flavor.
Overview:
Students will explore taste. The first half the lesson will deal with the biology and
physical structures in the tongue, such as taste buds, taste pores, and sensitivity to different
flavors. For this part, divide class into two groups and split them between part 1 and 2.
Then switch after 20 minutes. After class has complete parts 1 and 2, part 3 can be
completed for fun if you think there will still be time for part B. The second half will explore
the link between actual taste and perception of taste as influenced by the color of the flavor.
Introduction: (2 min)
What are the five senses? Today we are going to learn about taste. What do you know
about this sense? Why is it important? We are going to talk about how taste works and
what we can do to influence the flavor.
2
Making Sense: The Biology of the Senses
Spring 2008
Activity 1: The Tongue
Materials:
Light microscope, tongue slides, TV, tongue diagram, paper, digital camera, laptop
Part I: Light Microscope (20 min)
Procedure:
1. Place tongue cross-sectional slide under light microscope
2. Look at field of view projection on TV
3. Sketch tongue slide
Q: What angle are we looking at the tongue?
A: Explain that you can study the tongue topographically or cross-sectionally.
The benefit of studying topographically is that you can see the surface structures. The
benefits of cross-sectional displays are you can see the interworkings of the tongue, such
as the taste receptors and nerves. It is better for understanding the pathway.
Q: Do you know how the tongue works?
A: Explain the saliva dissolves the food and slides down into the taste pores. The taste
receptors are along the side. They are connected to the nerves, which send the signal to
the brain. Tie in idea that structures have different functions for growth and survival.
Explain that the tongue can more easily detect dangerous substances than the five
tastes. (e.g. 0.008 mM for quinine vs. 10mM for salt)
Q: How many different tastes are there?
A: Good time to bring up Umami.
Q: Where can you sense these tastes?
A: Everywhere although certain regions are more sensitive than others.
Q: If the food goes on your tongue, how does it get to your brain?
A: Start talking about perception since that is part of the next activity.
3
Making Sense: The Biology of the Senses
Spring 2008
Part 2: No such thing as a tongue map! (20 minutes)
Materials: bitter, sour, sweet, salty, and umami flavors, cotton swabs
Procedure:
1. See what kids know about taste. See if they have the misconception that taste is
mapped out on our tongues. If they have not learned about the tongue map, good.
Do not mention it to them. Just teach them that certain areas of the tongue are more
sensitive to different tastes, but everywhere on the tongue can taste these 5 basic
flavors. It is important to allow the kids to predict what will happen then you can
reconstruct their misconceptions if need be.
2. Have them draw out how they think
3. Allow children to test predictions by dabbing each flavor on their tongue one at a
time. Remember to stress changing one variable at a time.
4. Sketch whether different parts of the tongue were more sensitive to one taste rather
than another.
Part 3: Look at your own tongue! (5 minutes)
1. Take digital picture of mentee’s tongue
2. Upload to laptop
3. Examine tongue
Q: What do recognize on your tongue from the diagram?
A: About the only thing they will recognize are the fungiform papillae.
Q: Do you see any differences?
A: Make sure they know they know that the actual structures differ from diagrams.
They may notice that the actual tongue is not as clear-cut as the diagram. The bumps
will look fuzzy with nondescript borders.
4
Making Sense: The Biology of the Senses
Spring 2008
Activity 2: Taste of Color (20 minutes)
Materials: paper plate, fork or toothpick, napkins, access to 3 different flavors of gelatin,
glass of water, paper for recording observations
Procedure:
1. Obtain a cube of one of the three flavors of gelatin. Note whether it is A, B, or C.
Observe the cube and record its color.
2. Predict what the cube will taste like based on its color. Record your prediction
3. Taste the gelatin cube and determine its flavor. Record the flavor you perceive.
4. Rinse your mouth with a little water and swallow before you taste the next sample.
5. Repeat steps 1-4 for the other two flavors.
6. Convene as a class and pool data. Collect how many kids thought which flavor was
which.
7. Find out the true flavor of each gelatin sample. Is each one the flavor you thought it
was?
Q:
1. What flavor did you expect each gelatin cube to be?
2. Why did you anticipate the flavor?
3. Did the flavor you tasted agree with your expectation, or did you taste a
different flavor?
4. Based on your observations, what can you conclude about the influence of our
experiences on how we taste different foods?
5. Refer to previous tongue pictures, was there a link between more bumps and
more keen taste? Talk about supertasters (people who are super at tasting
because they have more bumps), tasters (normal people with average taste
and an average number of fungiform papillae), nontasters (people who don’t
mind vegetables because they can stand the bitter plant alkaloids)
5