Name: _________________________________________________________________
Lab: Skin Sensitivity
Date: _________________
Introduction:
The senses receive information about the environment and relay it to the central nervous system,
where the information is interpreted. The sense organs contain specializes neurons called receptors,
each of which is adapted to receive a particular kind of stimulus. Like all neurons, receptors follow the all
or none principle. That is, any stimulus that is weaker than the threshold will produce no impulse; any
stimulus that is as strong as or stronger than the threshold will produce an impulse. The threshold
minimum level of a stimulus that is required to activate a neuron.
The receptors for the sense of touch are scattered over the surface of the entire body. The
receptors, however, are more closely grouped together in some areas of the body than in others. In
addition, the receptors in one area may response to a weaker threshold than receptors in another area.
In this investigation you will study the distribution and sensitivity of the touch receptors in the
human body.
Hypothesis:
You will be taking samples from your fingertip, the palm of your hand, the back of your hand, the inside of
your forearm, and the back of your neck. Write a hypothesis stating the following:

**Which of these areas will be the most sensitive(therefore reach threshold the easiest)? Explain
why.

**Which of these areas will have the highest concentration of receptors? Explain why.
Record your hypothesis on your data sheet.
Materials:
 2 point calibers (yellow & blue)
 blindfold (or you can close your eyes)
 temperature probe
 metric ruler
 pencil
 blunt probe/pen
Methods:
Part A – Determining Threshold
1. Blindfold your partner or ask them to close their eyes.
2. Gently touch your partner on the fingertip with the metal probe. Your partner should tell you
whether he or she feels the touch of the probe. (you should only touch them lightly, do not POKE
them!)
3. Touch the probe to the fingertip 5 times. Record your data in Table 1. Place a check mark if the
stimulus was felt and leave the box blank, if the stimulus was not felt.
4. Repeat steps 2 and 3 for the palm, back of the hand, inside of the forearm, and back of the neck.
5. Switch roles with your partner and repeat all steps above.
Part B – Distinguishing Between 2 Stimuli
1. Obtain a 2 point caliper. Blindfold your partner (or ask them to close their eyes).
2. Gently touch your partner’s fingertip with the caliper when the two points are touching. Be very
careful when touching your partner’s skin; apply only a small amount of pressure. Have your partner
identify whether you are using 1 or 2 points. Record your data in Table 2.
3. Repeat step 2 with at measurements of 5mm, 10mm, 15mm, and 20mm. Use the sets of
measurements in ransom order so that you partner will not know the pattern in the testing. Use
the same amount of pressure every time. (ex: start with 15mm then do 5mm, then 10mm etc.)
4. Repeat steps 3 and 4 using the palm, back of the hand, inside of the forearm, and back of the neck.
5. Switch roles and repeat steps 2 through 6.
Part C – Locate a Stimulus
1. Blindfold your partner (or ask them to close their eyes).
2. With a marker, mark your partners fingertip so as to make a visible mark on the skin. Do not press
so hard as to break the skin. Make sure that if you are using a pencil, it has a rounded, blunt tip.
3. Have your partner try to touch the same point on his or her skin with a different color marker that
you touched with the first color.
4. Using the ruler, measure the distance between the 2 points and record your data in Table 3.
5. Repeat steps 2-4 two more times using points near, but not the same as, the first point. Record in
the data in Table 3.
6. Repeat steps 2 through 5 on the palm, back of the hand, inside of the forearm, and back of the
neck. *You are not required to use maker if you don’t want it on your skin. You may use a pencil or
pen or something that erases easily. It is your choice.
7. Switch roles and repeat steps 1 through 6.
Part D- Temperature Sensation
1. Place the aluminum temperature probe in cold water for a few minutes and allow it to get cold.
When the probe has cooled, remove it from the cold water and wipe it dry with a paper towel.
2. Your partner should have their eyes closed. Stamp the top of their hand with the grid. Lay your
partners hand with the palm facing down on the desk.
3. Begins in one quadrant of the dot grid and gently touch each dot with the temperature probe. The
probe should remain on each dot for about 2 seconds. Your partner should report whether or not
they feel a COLD stimulus. (not just pressure)
4. Repeat this activity, touching the other dots on the grid, reporting the sensation and recording the
response on the data sheet. Continue until all of the dots have been tested.
5. Repeat this procedure fro the palm and forearm locations and record the results. Remember that,
in order to analyze and interpret data correctly, it must be organized, complete, and recorded
accurately.
6. Repeat steps 1-5, this time using a warm temperature probe to map warmth receptors. Give the
sensor time to warm up and then follow the same protocol, mapping warmth receptors for the
back of the hand, palm, and forearm.
7. After completing this part of the lab, answer the questions.