14.2: Thermal Stressors (Worksheet)

Background

In the following laboratory activity, you will explore your body’s physical reaction to small-scale thermal stressors using two scientific procedures: the Minor Test, and Randall’s Modification to the Minor Test. Both tests explore sweat gland responses, but while the Minor Test is qualitative, Randall’s Modification is quantitative.

Upon completion of this activity, you will have:

• Explored the body’s ways of regulating temperature,
• Critically evaluated the difference between “adjustments” and “adaptations”
• Experienced and documented the body’s physical reaction to stressors.

Lab Kit Materials

• Timer
• Cold source (e.g. ice cubes, cold pack)
• Heat source (e.g. hair dryer, hand warmers)
• Blank paper cut into small squares of 3x3cm (4 per group)
• Cotton balls (24 per group)
• Rubbing alcohol
• Iodine
• Cornstarch

Instructions

This laboratory exercise consists of four experiments: (1) heat stress exposure, (2) cold stress exposure, (3) exercise/heart rate increase exposure, and (4) a control exercise with no stressor.

Each experiment should be undertaken by a different individual and assisted by their group members. Decide ahead of time which experiment (heat, cold, exercise, control) will be done by which group member. If there is a fifth group member, that individual should be the group’s recorder.

Additionally, ensure that you use a fresh cotton ball for each swab application to ensure no cross-contamination.

Part 1: Heat Stress - For Group Member #1

1. Using rubbing alcohol on a cotton ball, swab the left palm. Let it dry completely. Once the alcohol has dried, swab the same palm with iodine. Let the iodine dry completely.
2. Apply iodine to a fresh cotton ball and swab the right palm directly. Let it dry completely. Once the iodine has dried, apply cornstarch to the right palm using a fresh cotton ball.
3. Apply the heat source to both palms for 5 minutes. During this time, pay attention to any visual changes that occur on the right palm.
4. Once five minutes have elapsed, press a square of blank paper firmly into the left palm for approximately 30 seconds.
5. Record the number of dots you see on the paper pressed into the left palm in the respective box in the activity chart.
6. Record physical observations you see on the right palm in the respective box in the activity chart.
7. Record physical sensations or visual observations you made about your body during the experiment in the respective box in the activity chart.

Part 2: Cold Stress - For Group Member #2

1. Using rubbing alcohol on a cotton ball, swab the left palm, Let it dry completely. Once the alcohol has dried, swab the same palm with iodine. Let the iodine dry completely.
2. Apply iodine to a fresh cotton ball and swab the right palm directly. Let it dry completely. Once the iodine has dried, apply cornstarch to the right palm using a fresh cotton ball.
3. Apply the cold source to both palms for 5 minutes. During this time, pay attention to any visual changes that occur on the right palm.
4. Once five minutes have elapsed, press a square of blank paper firmly into the left palm for approximately 30 seconds.
5. Record the number of dots you see on the paper pressed into the left palm in the respective box in the activity chart.
6. Record physical observations you see on the right palm in the respective box in the activity chart.
7. Record physical sensations or visual observations you made about your body during the experiment in the respective box in the activity chart.

Part 3: Exercise Stress - For Group Member #3

1. Using rubbing alcohol on a cotton ball, swab the left palm, Let it dry completely. Once the alcohol has dried, swab the same palm with iodine. Let the iodine dry completely.
2. Apply iodine to a fresh cotton ball and swab the right palm directly. Let it dry completely. Once the iodine has dried, apply cornstarch to the right palm using a fresh cotton ball.
3. Perform jumping jacks for 5 minutes. During this time, pay attention to any visual changes that occur on the right palm.
4. Once five minutes have elapsed, press a square of blank paper firmly into the left palm for approximately 30 seconds.
5. Record the number of dots you see on the paper pressed into the left palm in the respective box in the activity chart.
6. Record physical observations you see on the right palm in the respective box in the activity chart.
7. Clean both palms with a cotton ball and rubbing alcohol.
8. Record physical sensations or visual observations you made about your body during the experiment in the respective box in the activity chart.

Part 4: Control With No Stress - For Group Member #4

1. Using rubbing alcohol on a cotton ball, swab the left palm, Let it dry completely. Once the alcohol has dried, swab the same palm with iodine. Let the iodine dry completely.
2. Apply iodine to a fresh cotton ball and swab the right palm directly. Let it dry completely. Once the iodine has dried, apply cornstarch to the right palm using a fresh cotton ball.
3. Rest for 5 minutes. During this time, pay attention to any visual changes that occur on the right palm.
4. Once five minutes have elapsed, press a square of blank paper firmly into the left palm for approximately 30 seconds.
5. Record the number of dots you see on the paper pressed into the left palm in the respective box in the activity chart.
6. Record physical observations you see on the right palm in the respective box in the activity chart.
7. Record physical sensations or visual observations you made about your body during the experiment in the respective box in the activity chart.

Observations

Reflection

After you have recorded your observations in the table above, discuss the following questions with your group:

1. What do the dots on the paper pressed to the left palm represent?
2. What does a color change on the right palm represent?
3. What does sweating accomplish for the body?
4. What does shivering accomplish for the body?
5. How is body temperature regulated in humans?
6. What are the differences between “adjustments” and “adaptations”? How are they relevant to understanding human evolution?
7. Why do we turn paler in response to cold, and redder in response to heat?