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Whelmer #25: Inch of Skin


Illustration of a pencil probing the back of someone's hand.Description:
Students locate different types of nerve receptors in their skin.

Science process skills:

  1. observation
  2. classification
  3. communication
  4. prediction
  5. inference
  6. and interpreting data
Complex reasoning strategies:
  1. comparison
  2. classification
  3. induction
  4. problem solving
Standards:
K-4:
  • Employ simple equipment and tools to gather data and extend the senses (Standard A.1.3).
  • Each animal has different structures that serve different functions in growth, survival, and reproduction (Standard C.1.2).
  • Humans and other organisms have senses that help them detect internal and external cues (Standard C.1.3).
5-8:
  • Living systems at all levels of organization demonstrate the complementary nature of structure and function (Standard C.1.1).
  • Specialized cells perform specialized functions in multicellular organisms. Each type of cell, tissue, and organ has a distinct structure and set of functions that serve the organism as a whole (Standard C.1.4).
  • The human organisms has systems for protection (Standard C.1.5).
  • Regulation of an organism's internal environment involves sensing the internal environment and changing physiological activities to keep conditions within the range required to survive (Standard C.3.2).
9-12:
  • Multicellular animals have nervous systems that generate behavior. Nervous systems are formed from specialized cells that conduct signals rapidly through the long cell extensions that make up nerves. In sense organs, specialized cells detect light, sound, and specific chemicals and enable animals to monitor what is going on in the world around them (Standard C.6.1).
Above Standards from the National Science Education Standards.

Content topics:
  1. human nervous system
  2. nerve receptors
  3. graphing
You will need:
  1. washable marker or crayon
  2. sharp pencil or bamboo skewer
  3. graph paper
  4. ruler
Instructions:
Use the ruler and a washable marker to draw a one inch square on the back of each student's hand.

Use the sharp end of a pencil or bamboo skewer to gently poke the skin at any point within the one inch square boundary, being s ure not to break the skin. Direct students to take careful notice the sensation as they gently push the pointed end of the pencil on their skin.

Move the point of the pencil one or two millimeters in any direction and push again. Make note of the sensation. At some sites within the square inch students will detect a cold feeling. At other sites the pencil point will feel hot, pointed and painful, or there will be no sensation at all.

Students can plot the sites of various sensations on graph paper. Use different colored markers or letter designations indicated the sensation felt at various sites.

Presentation:
It is not the intent of this activity to inflict pain. Students are not to break the skin or cause any injury. Take the precaution to direct students to follow your instructions carefully.

Ask students to list the various sensations they feel at different sites. Ask them to explain how the point of the pencil could feel different. What changes from site to site? Does the pencil change?

Content:
There are different types of nerve receptors in the skin. Some receptors detect pressure. Others detect heat, cold and pain. If a student pushes the pencil point near a "cold" receptor, the point feels cool. At another site the point feels much sharper but not cold.

Most high school books include a cross section diagram of skin. Students will notice that in some areas of the skin, there is much space between the receptors. In other areas, such as skin over the lips, the receptors are bunched close together. That is why lips are very sensitive.

Assessment:
Type: small group.
Content/Process: nervous system, nerve receptors.
Age/Level: all.

Mark off four square-inch areas on your hand, arm, or other exposed area of skin. If it is convenient, the bottom of the foot could be used. Predict which area will have the most of each kind of receptor. Record your data along with a justification of your predictions. Perform the activity again on these four areas. Compare it to your predictions. Discuss orally or in written form where on your body these specific receptors occur most often and why it is beneficial to the human organism to have them distributed in this manner. Young children could graph their results and explain their findings to the class. Compare group results and let students discuss them in relation to how the distribution of these receptors benefits them.


Notes:





  
     
 

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