Assessing skin sensitivity – temperature receptors
Class practical
This procedure has been developed with the help of the Physiological Society.
This procedure allows you to explore the subtlety of information about our surroundings collected by receptors in our skin.
Lesson organisation
It would be good to arrange for everyone to experience the first part of the investigation – the effect of simultaneously putting both hands in a bowl of room temperature water after holding one in cold and one in warm water for 2 minutes.
In the second part, one student should test another student’s responses to the hot and cold thermometers. If there is time, you can reverse the roles.
Apparatus and Chemicals
For each group of students:
Access to a water bath at 45 °C
Access to a bowl of iced water
Access to a bowl of water at room temperature
Thermometer (in water bath at 45 °C), 1
Thermometer (in bowl of iced water), 1
Health & Safety and Technical notes
Read our standard health & safety guidance
Use a thermometer containing alcohol for preference. If using mercury thermometers, the small amount of mercury contained in a thermometer does not constitute a serious health risk, though all breakages and spills should be cleared up immediately (see CLEAPSS Laboratory Handbook section 7.7 for much more detail). The stems and bulbs of broken thermometers and collected mercury droplets should be placed in a closed plastic container, suitably labelled ‘Mercury waste - For disposal by a licensed contractor’. This can be kept until other chemicals are to be disposed of.
Ethical issues
Students are test subjects for this practical and so should sign the attached form to state that they understand the procedure, agree to be involved, and have the right to stop their participation and remove their results at any time.
Procedure
SAFETY: Students should touch one another carefully and without causing damage. It should not damage students without circulatory problems to put one hand in iced water for 2 minutes and one in water at 45 °C.
Preparation
a Decide on the roles of the students in each working group
b Ensure that the student whose temperature sensitivity is to be assessed has understood the procedure and signed the student briefing and consent sheet.
Investigation
c Place one hand in the water bath at 45 °C and the other in the bowl of iced water for 2 minutes.
d Put both hands together into the bowl of water at room temperature.
e Describe how the water feels to each hand.
f Allow the feeling in both hands to get back to normal.
g Take a thermometer from the water bath at 45 °C and wipe it dry. Touch it on the back of a hand in different places.
h Record whether some warmth is felt as well as the touch, or whether only the touch is sensed. When only touch is sensed, record the temperature reading from the thermometer.
i Repeat with a thermometer from the iced water. Dry the thermometer and touch it on the back of a hand in different places. Record whether the cold is felt as well as the touch, or whether only the touch is sensed. When only touch is sensed, record the reading from the thermometer.
Teaching notes
In the first investigation, we become accustomed to the temperature of the ice cold water or the 45 °C water. When we put our hands together into the room temperature water, it feels warm to one hand and cool to the other.
The highest reading on the cold thermometer and the lowest reading on the warm thermometer mark the ends of the ‘thermoneutral’ range of the skin sensitivity. In this range we detect only touch, and are not aware of temperature. This is likely to be around 20 °C for most of us. Think about the consequences of this in terms of our preferred temperature for our surroundings – where we won’t feel hot or cold. This might affect how we like to set our thermostats at home.
Health & Safety checked, March 2009
Downloads
Download the student briefing and consent sheet 
Assessing skin sensitivity - temperature receptors (52KB).
Related experiments
Other practicals on the site explore different aspects of the sensitivity of the skin.