Biology Sensitivity Lab Report

To investigate the effect of skin sensitivity In response to cold temperature in different parts of the body by timing the maximum amount of time in which Ice-pack can be held to that area. Hypothesis: If the layer of skin Is relatively thin, the nerve response to cold will be the fastest, Increasing the skin's sensitivity. This therefore means that the fastest responses to cold will be in the face, and specifically the nose.

The skin consists of 3 main layers; the epidermis, dermis and hypodermic (also known as the subcutaneous). The epidermis consists of dead and nearly dead skin cells which protects us from injury, infections, fluid loss... Acting as a barrier. The Dermis is the skin layer which contains most of the nerve cells, hair follicles, sweat glands and many others. The Hypodermic layer is not really a skin layer, it attaches the skin to everything else; it contains the fat layer.

The layer of fat in the nose's hypodermic is very thin in relation to other parts of the body which will make the nerves detect the change in temperature on the surface the fastest, therefore bringing upon the response In less time. Variables: Independent variable: The part of the body (area of skin). Dependent variable: The maximum amount of time the ice-pack can be held to the skin (Using a stopwatch).

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Controlled variables: * The same height group (1 55-CACM) * The same weight group (45-keg) * The same age group (15-20) * The same sex (female) * The same temperature of the Ice-pack (placed In the freezer for 5 hours) * The same surrounding temperature (20-ICC) The same body temperature (3709 ; The same material used in the icepack( plastic and gel) ; The same size and thickness of the icepack (medium sized) Fair test: This experiment is considered to be a fair test because I think that most of the rabbles that can manipulate the results in any way other than the variable which I want to manipulate which is area of skin being tested, for example the height group and age group are controlled which ensures that the layer of fat in different people is similar due to these characteristics. Materials: * 3 ice-packs of the same temperature * Stopwatch * Thermometer * A long table Method: 1 . Place 3 identical icepacks in the freezer for 2 hours before starting the 3. Take their temperature making sure it is around ICC (If not change one of the people to one with all the requirements including temperature). 4. Make the person lay on the table on her back. 5.

Take out one of the icepacks from the freezer. 6. Place the icepack on the thigh and time the time needed for the person to reach his limits with the cold. 7. Repeat the above step for the other body parts (Upper arm, belly, forearm, forehead and nose). 8. Replace the ice pack in the freezer again and take out another one. 9. Repeat the experiment on the same person another time. 10. Replace the second ice pack and repeat the step above with the third icepack. 11. Replace the ice pack in the freezer. 12. Wait for an hour to regulate the temperature of the ice packs in the freezer. 13. Repeat steps 3-10 for the second female. 14. Record the result throughout the whole process. 15.

The results are not completely constant though since the belly normally has more fat than the upper arm, but since the belly was covered with a shirt beforehand this led to tampering in the reliability of the experiment which is noninsured a source of error. The thermo receptors face's skin is the most responsive to temperature changes; the forehead had an average response time of 17 seconds. I came up with an average for each person's tree trials first, and then I came up with a final set of data for the average of all 6 trials on the two people. I came up with the final average by adding up all the 6 results from the several trials and divide them by 6 giving us a final result that we can work with to draw conclusions about our results and their reliability. Data presentation: Conclusion:

My main conclusion from this experiment about skin sensitivity in different areas in response to cold temperature changes is that the skin on the nose is the most affected. This is because of two things, the main reason being the layer of fat on the nose is a lot thinner than the layer of fat on other parts of the body like the thigh and the second reason being that thermo receptors which are the nerve cells which respond to temperature changes in the surrounding are highly concentrated in the face area so the fastest responses would therefore surely be from the face, explaining the fastest two reactions; nose (an average of 9 seconds) and forehead (an average of 17 seconds). This supports my hypothesis since that was my initial thought regarding the experiments' results due to scientific research.

My results are highly valid since they make sense and are backed up with concrete scientific reasoning. The face brought upon the fastest responses followed by the belly and the arm. The belly has a thicker layer of fat than the arm; this is where my results got a bit mixed up since the people tested were wearing shirts which warmed them up fore starting which brought a faster response due to the bigger gap in change of temperature. The thigh had the slowest response time of an average of 163, which is logical since the thigh has the thickest layer of fat between the areas tested. Evaluation: In general I think my method was pretty valid since I controlled all the factors and explained the method in which I did.

In my method I also showed steps of finding the average for the data collected which makes my results more reliable since they become more accurate. I also made the person getting tested to lie on a flat surface o that the icepack would be even on her body and won't move or fall down. Sources of error: 1 . The skin temperature was not constant all over the body since the belly for example was covered with a shirt. 2. The Ice-pack got warmer, so the last tests were less reliable. 3. The pressure applied to the ice-pack was altered and not completely constant. 4. The difference between the reaction time of the forehead Improvements: 1 . The test should only be performed on parts of the body exposed completely, not the ones covered with clothes.

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