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6-8 > Human Body
Grade level: 6-8 Subject: Human Body Duration: One class period
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The Brain: Perception

Students will understand the following:
1. The brain links our sense of taste with our sense of smell.
2. The tongue can determine only four basic tastes: salty, sour, bitter, and sweet.
3. All the more subtle tastes we experience are largely a function of olfactory senses, or smell.

Each group will need the following materials:
Variety of substances to taste, including raw onion and raw potato
Prepared list of the substances to be tasted (copy for each student)

1. Ask your students if they are certain that they could distinguish a slice of raw potato from a slice of raw onion in a blindfolded taste test. Then ask them if they could distinguish between the two tastes while blindfoldedandholding their noses.
2. Tell students they are going to perform a test to find out if their predictions were correct and then discuss the reasons for the results.
3. Have students form two groups. One group will hold their noses while blindfolded and taste various substances, including raw potato and raw onion. The other group will taste the same substances while merely blindfolded.
4. Have each student from one group, then the other, take the taste test. Instruct students to try to identify each substance but to say, “I don’t know,” if they have no idea what the substance is. As each student takes the test, check off on his or her list which substances are correctly identified, which are incorrectly identified, and which get an “I don’t know.” (You may prefer to appoint students to administer the tests.)
5. Appoint a small group of students to compile the results of the test. How many correct identifications of each substance were made by students holding their noses compared with the number of correct identifications made by students able to smell?
6. Discuss the results with the class, leading students to infer that smell and taste are linked.
7. Encourage students to do further research on the relationship between smell and taste, or explain to them that the tongue can distinguish only four basic tastes—salty, sour, bitter, and sweet. All the more subtle tastes we experience are largely a function of our sense of smell.
8. Have each student write a paragraph describing the experiment and his or her own personal experience while taking the test.
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Adaptations for Older Students:
Older students can research, in greater depth, the physiology of taste and smell.
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Discussion Questions

1. Compare the brain's coordination of depth perception and location of sound.
2. Describe how olfactory impairment (even holding one's nose) could affect taste perception.
3. Discuss how technology has improved our ability to perceive ourselves.
4. Discuss how experiences, emotions and cultural patterns affect people's perceptions, and how perceptions may affect a culture. How might this explain the existence of certain prejudices?
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You can evaluate your students on their paragraphs using the following three-point rubric:
Three points:paragraph clear, complete, well organized, and error-free
Two points:paragraph clear, incomplete, sufficiently well organized, with some errors
One point:paragraph unclear, incomplete, lacking in organization, with numerous errors
You can ask your students to contribute to the assessment rubric by determining an organizational plan for the report.
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Two Is Better Than One
What is the advantage to having two eyes and two ears? Have students pair up with partners and, with the use of eye patches and cotton earplugs, devise a test to demonstrate what sensory input is necessary for the brain to coordinate depth perception and sound direction. Such tests could involve visually estimating the distance of a pencil and guessing the direction of a sound, such as finger snapping.

Scents and Memories
Tell students that many people think that our sense of smell brings back memories from the past more than any other sense—even sight and hearing. Let students experiment to find out if their own senses of smell bring back memories of past experiences. Have on hand a variety of substances to smell. Ask students to pair up with partners and take turns being blindfolded. The blindfolded partner must describe each smell and any memories evoked by the smell. Students will be interested to learn that olfactory neurons (nerve cells that send smell messages to our brains) are linked to the limbic system, which is the part of the brain that influences emotion and memory.

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Suggested Readings

Your Brain: How You Got It and How It Works
Tabitha M. Powledge, Scribner's, 1994
A medical book that explains in accessible terminology how the brain processes sensory information, how it learns, and how memory works. One of the few serious books targeted specifically to young people.

"Nature, Nurture, Brains, and Behavior"
Kenneth J. Mack, World and I, July 1996
This article covers the very latest determinations about the combined impact of genetics and environment on brain development, including hypotheses about the prevention of Alzheimer's disease.

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The Whole Brain Atlas
Designed as a learning tool for medical school students, this fascinating atlas offers images of healthy and diseased human brains.

Brain and Behavior
Part of the Serendip Home Page. On this site there are many activities to test your perception abilities.

The Joy of Visual Perception: A Web Book
This web book uses graphics supplemented with text to stimulate interest in the sense of vision.

Exploratorium Exhibits
The online exhibit area of the Exploratorium, a museum of science, art, and human perception in San Francisco.

Science Center Lesson - The Five Senses - Sight
Three complete lesson plans on how to teach the sense of sight to elementary students.


Science Center Lesson - The Five Senses - Touch
Four complete lesson plans on how to teach the sense of touch to elementary students.


The Brain--Our Universe Within

About Brain Injury: A glossery of terms

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Click on any of the vocabulary words below to hear them pronounced and used in a sentence.

speaker    perception
Definition:Understanding or insight.
Context:How in the world do we make sense of the world? We do it with something called perception.

speaker    rods and cones
Definition:The portion of the retina ("back wall") which gathers incoming light and converts it to electric impulses for use by the brain.
Context:Incoming light is converted to electricity by these strange devices called rods and cones.

speaker    cerebral cortex
Definition:The extensive outer layer of gray tissue that covers the cerebrum and is largely responsible for higher nervous functions.
Context:The cerebral cortex, the brain's quarter-inch thinking cap, consists of tightly packed columns of nerve cells.

speaker    neurons
Definition:Any of the cells of nerve tissue consisting of a main portion containing the nucleus and cytoplasmic extensions, the cell body, the dendrites, and axons.
Context:All of these visual bits and pieces are processed and coded by assigned neurons.

speaker    adapt
Definition:To adjust to a specified use or situation.
Context:But the human brain, even when damaged, has a remarkable ability to adapt. When one sense fails, we can rely on another.

speaker    olfactory
Definition:Of or pertaining to the sense of smell.
Context:Odor molecules sniffed through the nose or pumped up the tongue and cheeks through the nasal cavity are picked up by cilia or tiny hairlike projections of the olfactory neurons.

speaker    limbic
Definition:A system, dispersed throughout the forebrain, composed of the thalamus, hypothalamus, amygdala, hippocampus, and parts of the cortex. It influences emotion and memory.
Context:Though they are spread throughout the cortex, olfactory neurons have particular circuits wired to the limbic system.

speaker    endocrine
Definition:The system of organs that secrete hormones into the blood to regulate basic functions of cells and tissues. The endocrine organs are the anterior and posterior pituitary glands, thyroid and parathyroid glands, pancreas, adrenal glands, ovaries (in women) and testicles (in men).
Context:Though they are spread throughout the cortex, olfactory neurons have particular circuits wired to the limbic system--that's where our emotions sit--and to the endocrine system--where hormones are produced.

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This lesson plan may be used to address the academic standards listed below. These standards are drawn from Content Knowledge: A Compendium of Standards and Benchmarks for K-12 Education: 2nd Edition and have been provided courtesy of theMid-continent Research for Education and Learningin Aurora, Colorado.
Grade level:9-12
Subject area:life science
Knows the general structure and functions of cells in organisms.
Knows that most cell functions involve chemical reactions; food molecules taken into cells are broken down to provide the chemical constituents needed to synthesize other molecules; both breakdown and synthesis are made possible by a large set of protein catalysts called enzymes.

Grade level:9-12
Subject area:life science
Knows the general structure and functions of cells in organisms.
Knows that multicellular animals have nervous systems to generate behavior; nervous systems are formed from specialized cells that conduct signals rapidly through the long cell extensions that make up nerves, and the nerve cells communicate with each other by secreting specific excitatory and inhibitory molecules.

Grade level:9-12
Subject area:life science
Knows about the diversity and unity that characterize life.
Knows that organisms are classified into a hierarchy of groups and subgroups based on their similarities and reflecting their evolutionary relationships; the similarity of organisms inferred from similarity in their molecular structure closely matches the classification based on anatomical similarities.

Grade level:9-12
Subject area:life science
Knows about the diversity and unity that characterize life.
Knows that the variation of organisms within a species increases the likelihood that at least some members of the species will survive under changed environmental conditions, and a great diversity of species increases the chance that at least some living things will survive in the face of large changes in the environment.

Grade level:9-12
Subject area:physical science
Understands energy types, sources, and conversions, and their relationship to heat and temperature.
Knows that the energy of waves (electromagnetic and material) can be changed to other forms of energy (e.g., chemical and electrical), just as other forms of energy (chemical and nuclear) can be transformed into wave energy.

Grade level:9-12
Subject area:technology
Understands the nature of scientific knowledge.
Knows that because all scientific ideas depend on experimental and observational confirmation, all scientific knowledge is, in principle, subject to change as new evidence becomes available; in areas where data, information, or understanding is incomplete, it is normal for scientific ideas to be incomplete, but this is also where the opportunity for making advances may be the greatest.

Grade level:9-12
Subject area:technology
Understands the nature of scientific inquiry.
Knows that results of scientific inquiry--new knowledge and methods--emerge from different types of investigations and public communication among scientists; the nature of communicating and defending the results of scientific inquiry is guided by criteria of being logical and empirical and by connections between natural phenomena, investigations, and the historical body of scientific knowledge.

Grade level:9-12
Subject area:technology
Understands the interactions of science, technology, and society.
Knows that science often advances with the introduction of new technologies and solving technological problems often results in new scientific knowledge; new technologies often extend the current levels of scientific understanding and introduce new arenas of research.

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Louise Roy Fowler, science teacher, Oakcrest School, Washington, D.C.
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