Reach Out and Touch Someone

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Shut your eyes. What can you feel? Touch, pressure, heat, or cold? All these sensations are your brain's interpretation of signals it receives from your skin. Here's a simple exploration you can do to measure your sense of touch.

In this activity you'll explore National Science Education Content Standard C: Life Science - Structure and function

Middle School:

Specialized cells perform specialized functions in multicellular organisms. Groups of specialized cells cooperate to form a tissue, such as a muscle. Different tissues are, in turn, grouped together to form larger functional units, called organs. Each type of cell, tissue, and organ has a distant structure and set of functions that serve the organism as a whole.

Behavior is one kind of response an organism can make to an internal or environmental stimulus. A behavioral response requires coordination and communication at many levels, including cells, organ systems, and whole organisms. Behavioral response is a set of actions determined in part by heredity and in part from experience.

High School:

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. The nerve cells communicate with each other by secreting specific excitatory and inhibitory molecules. In sense organs, specialized cells detect light, sound, and specific chemicals and enable animals to monitor what is going on in the world about them.

What You'll Need:

• Two "picks" used for hair rollers or the ends of two paper clips that you've partially opened
• A millimeter ruler
• Eye protection

Keeping Safe:

Whenever there is a chance of any object coming near the eyes wear eye protection. Don't forget to wash or sterilize it between uses.

Procedure:

Find a partner. Ask your partner to shut his or her eyes. Then very gently place two points on the skin on the back of your partner's hands, 5 mm apart. Ask: "Can you feel two points or one?" (Most students will be able to tell that there are two points.)

Next, try to find the minimum distance that a student can distinguish two points instead of one. Do this by trying to place your points 4 mm apart, then 3 mm, 2 mm, and 1 mm from each other. Record your subject's response on the table below.

Next try the same experiment on the top and bottom of the forearm. Is there a difference?

Finally, ask your partner to put on eye protection (just in case!) and try it on the cheek.

Two Points or One?

Questions:

1. In which area of the skin are touch receptors closest?

2. What is the survival value of touch receptors?

3. Is there any part of the body where touch receptors would be a disadvantage?

Answers:

1. The top of the forearm and the cheek are most sensitive to a light touch.

2. Response to danger and a soothing effect in the young (releasing brain endorphins) are two possibilities.

3. The soles of the feet would be one area.