TITLE OF LESSON PLAN:
The Incredible Human Body: The Five Senses

LENGTH OF LESSON:
Two to three class periods

GRADE LEVEL:
9-12

SUBJECT AREA:
Human Body

CREDIT:
Jordan D. Brown, freelance writer in New York City, author of educational books, magazine articles, and Web content.

OBJECTIVES:
Students will

1. understand how each of the five senses works and define the related terminology

2. compare and contrast the means by which the senses gather information about the world

3. investigate a research question, analyze the results, and present the findings

MATERIALS:
Each group will need the following:

Reference materials about the five senses (books and Web sites suggested below)

Poster board or large sheets of paper

Construction paper

Colored markers

NOTE: In addition, each group will probably need additional materials to supplement its presentations. For example, for a presentation about smell, the group may gather samples of different “mystery smells” for the class to decipher.

PROCEDURE:

1. As a class, review the five senses (sight, hearing, smell, taste, and touch). Have a brief preliminary discussion about how each sense works.

2. Divide students into five groups, with four to five students in each group. Assign each group one of the five senses. Explain that each group will research how the assigned sense works and will create a labeled picture that illustrates this process. In addition, each group will select a question about the sense, then research the answer.

3. Here are some examples of possible research questions for each sense. Each group should select at least oneof the questions they wish to explore.
  
SIGHT

-  Why do some people need glasses? How do glasses improve vision?
-  What causes nearsightedness? How is it different from farsightedness?
-  How does corrective laser eye surgery work? How does it improve vision? What risks are involved?
-  Why are some people colorblind?
-  How do optical illusions work? How do they “fool” your brain?
-  How do red-and-blue “3D glasses” work?
HEARING

-  How do sounds reach the brain?
-  Why do some sounds have a low pitch, while others have a high pitch?
-  Why are animals such as dogs able to hear sounds that humans cannot?
-  When someone is “hard of hearing,” what are some possible causes?
SMELL

-  Why do certain smells instantly evoke specific memories or feelings?
-  How are the senses of smell and taste related? 
-  If you hold your nose while eating, how are tastes affected? Why?
TASTE

-  How do taste buds work? How does the tongue recognize different tastes, such as the bitterness of a lemon or the sweetness of sugar?
-  Which taste cannot be detected by the tip of your tongue: bitter, sour, salty, or sweet? Why?
TOUCH

-  How does your hand tell the difference between hot and cold surfaces?
-  How do blind people use braille to read?

4. Each group gives a class presentation using its diagram, any other visual aids, and any additional supporting materials. Each presentation should begin by explaining how the particular sense works. Then, using a demonstration of some sort, the group will answer one of the research questions. Students are encouraged to create sensory experiences for the whole class that demonstrate the biological principles associated with the sense.

ADAPTATIONS:

Sense-ational Scenarios
To help younger students comprehend how the different senses work, have them role-play the various parts of the sensory organs as a class demonstration. For example, to illustrate how the eye responds to a sudden shift in light, ask a group of students to role play these body parts:

-  Pupil
-  Lens
-  Retina
-  Rod and cone cells
-  Fovea (area of sharpest vision on retina)
-  Optic nerve
-  Brain
Once each student understands the basics of how his or her part works, present a few scenarios and see how the different parts would respond. For example, when the eye is in a dark room, the pupil is enlarged (to let more light in). If a bright light were suddenly turned on, which of the parts would change and in what ways? For one thing, the pupil would get much smaller. Also, the cones in the retina would respond to the images in the room. Similar scenarios can be created for each of the five senses.

DISCUSSION QUESTIONS:

1. Discuss the important role that the brain plays in sensing the world.

2. Brainstorm a list of inventions that humans have come up with to enhance sensory abilities (e.g., glasses, hearing aids).

3. Explain why the sense of smell has the ability to evoke distant memories.

4. Debate which of the senses is most essential. Which of the senses do you think it would be hardest to survive without?

5. Although the human nose can distinguish up to 10,000 different smells, many smells are hard to put into words. Hypothesize why such smells are hard to describe.

6. Often when a person loses one of the senses (e.g., sight or hearing), the other senses intensify and become more effective at perceiving the world. Discuss why this phenomenon occurs.

EVALUATION:

Before the group presentations, work with students to develop a series of criteria for evaluating the sense projects. Discuss what factors would make a top-notch presentation (such as factual accuracy, answering the research question, use of correct vocabulary, level of research, clarity of visuals, involving the whole class, creative demonstrations). Once the class determines the criteria, create a handout of these criteria with a 1-5 scale next to each item. As students work on their presentations, encourage them to review the criteria to make sure they are meeting every one. During the presentation, the teacher and the students in the other groups evaluate the presentation using this rubric.

EXTENSION:

IF YOU COULD SENSE LIKE THE ANIMALS
Although humans do a superb job at sensing the world, there are other members of the animal kingdom that do it better. For example, because a dog has about 200 million smell cells in its nose (versus 5 million in the human nose), it can pick up much fainter scents. Salmon, too, have remarkable noses. By smelling the ocean, they can swim their way back to the exact stream in which they were born years before. Snakes smell out their meals with their tongues. Scientists have figured out that birds can navigate across large distances by detecting Earth's magnetic field. For each of the five senses, find at least two interesting comparisons within the animal world.

PHANTOM LIMBS AND MORE
People who have lost an arm or a leg often perceive the limb as though it is still there. Similarly, some people who have lost the ability to see or hear occasionally experience sights and sounds. How is this possible? Research these phenomena and present your findings to the class. A good place to start your research are these sites:
  
Phantom Limbs
  
Phantom Seeing and Hearing

SUGGESTED READINGS:

A Natural History of the Senses
Diane Ackerman. Vintage Books, 1991

The Magic School Bus Explores the Senses
Joanna Cole and Bruce Degen. Scholastic Press, 1999.

Animal Senses : How Animals See, Hear, Taste, Smell, and Feel
Pamela Hickman. Kids Can Press, 1998.

WEB LINKS:

Seeing, Hearing, and Smelling the World

http://www.hhmi.org/senses/

Come to Your Senses

http://tqjunior.thinkquest.org/3750/

Ten Activities for Teaching the Five Senses

http://www.education-world.com/a_lesson/lesson183.shtml

Great Sites for Teaching about the Five Senses

http://www.education-world.com/a_sites/sites020.shtml

The Nose Knows

http://www.exploratorium.edu/ti/human_body/nose.html

Museum of Opthamology

http://www.eyenet.org/public/museum/discover.html

VOCABULARY:

cochlea
Shaped like a snail's shell, this part of the ear receives vibrations.
Context:
Vibrations in the inner ear are channeled through the cochlea, stimulating nerve impulses to the brain.

eardrum
A stretchy membrane, located at the end of the ear canal, that vibrates when it detects sound waves.
Context:
Sound waves strike the eardrum, sending vibrations to the middle ear.

lens
The part of the eye, located just behind the pupil and iris, that directs light to the back of the eye (retina).
Context:
The lens of the eye focuses light onto the retina.

olfactory nerve
The nerve, located at the top of the inner nose, that sends odors to the brain.
Context:
Odor chemicals from the air stimulate fibers of the olfactory nerve, sending impulses to the brain.

pupil
The opening in the front of the eye that lets in light.
Context:
The size of the pupil controls the amount of light entering the eye.

retina
The thin lining of cells, located in the back of the eye, that translates light patterns into nerve signals, which are sent to the brain.
Context:
The retina contains millions of light-sensitive cells that convert light into nerve impulses to the brain.

sensory receptors
Sensors, located beneath the skin, that send nerve messages to the “touch” center of the brain.
Context:
Sensory receptors for heat and cold are found directly below the surface of your skin.

ACADEMIC STANDARDS:

Grade Level:
9-12
Subject Area:
Science and Technology

Standard:
Understands the nature of scientific inquiry.

Benchmarks:
Knows that investigations and public communication among scientists must meet certain criteria in order to result in new knowledge and methods (e.g., arguments must be logical and demonstrate connections between natural phenomena, investigations, and the historical body of scientific knowledge; the methods and procedures used to obtain evidence must be clearly reported to enhance opportunities for further investigation).

Grade Level:
9-12
Subject Area:
Life Sciences

Standard:
Understands the nature of scientific inquiry.

Benchmarks:
Knows that scientists conduct investigations for a variety of reasons (e.g., to discover new aspects of the natural world, to explain recently observed phenomena, to test the conclusions of prior investigations, to test the predictions of current theories).

Grade Level:
9-12
Subject Area:
Life Sciences

Standard:
Knows the general structure and functions of cells in organisms.

Benchmarks:
Knows the structures of different types of cell parts (e.g., cell wall; cell membrane; cytoplasm; cell organelles such as the nucleus, chloroplast, mitochondrion, Golgi apparatus, vacuole) and the functions they perform (e.g., transportation of materials, storage of genetic information, photosynthesis and respiration, synthesis of new molecules, waste disposal).

Grade Level:
9-12
Subject Area:
Science and Technology

Standard:
Understands the nature of scientific inquiry.

Benchmarks:
Uses technology (e.g., hand tools, measuring instruments, calculators, computers) and mathematics (e.g., measurement, formulas, charts, graphs) to perform accurate scientific investigations and communications.

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