Presentation on theme: "Carolina Biological $89.50. Background Information Body temperature is the balance between heat production and heat loss. The temperature of the skin."— Presentation transcript:
Background Information Body temperature is the balance between heat production and heat loss. The temperature of the skin plays a role in determining the rate at which body heat is gained or lost. Peripheral blood flow is blood flow to the superficial tissues. Heat elimination depends on the amount of peripheral blood flow at any given time.
Heat exchange across the body is not uniform depending on the amount of blood vessels in any given area. Peripheral circulation is controlled by the autonomic nervous system and influenced by the hypothalamus. Peripheral circulation can conserve body heat in cold environments (blood vessels constrict) or eliminate excess heat in warm environments (blood vessels dilate)
Liquid Crystals Special molecules Temperature variations alter the shapes of the liquid crystal molecules The change in shape alters the wavelengths of light the crystals reflect
By using liquid crystals and observing color changes we will be able to accurately measure temperatures temperature gradients temperature changes
Carolina crystals have a two degree wide operating range Allows for one degree above and one degree below event temperature on the thermographic sheets Thermographic sheets in this kit respond to skin temperatures of approximately 28 o C 30 o C 32 o C 33 o C 34 o C
How the thermographic sheets work An initial brownish color appears while the crystals are warming up Yellow is a transitional color The color transition is red-green-blue Green signifies when the event temperature has been reached Example If you are using a 32 o C thermographic sheet, any green areas will be approximately 32 o C; brownish-red areas will be cooler than 32 o C and blue areas will be warmer than 32 o C
Important Note Do not directly touch the thermographic sheets (this may alter your temperature readings)
Roles in the lab Experimenter Applies the thermographic sheet to the test subjects hand Test Subject
Procedure Part A: Regional Variations Experimenter selects thermographic sheet and applies it to the back of the test subjects hand. If the sheet turns a uniform dark blue, the Experimenter should choose a sheet with a higher event temperature. The goal is to select a sheet that undergoes a gradual, distinct color change when placed on the test subject’s hand. Observe the color pattern that emerges on the sheet. Repeat using different body locations, such as: the cheek, the forehead, the neck, the knee, and the inside of the forearm
What caused the blue lines of streaks to appear on the liquid crystal sheet when it was placed on the back of the hand? Based on your observations, which areas of the body were the warmest?
Part B: Effects of Gravity Test subject to raise arm to chest level and extend outward to side (maintain this position) Experiment places thermographic sheet on back of test subjects hand As sheet stabilizes look for blue vein patterns With sheet still in place test subject should extend hand straight up in the air for 1 minute Watch for changes in color pattern in areas overlying the veins. Return to initial position and watch the colors stabilize Test subject should then lower arm to side for 1 minute Watch for changes in color pattern in areas overlying the veins.
What accounts for the color change when the hand is raised above the head? What accounts for the color change when the hand is lowered to the side?
Part C: Effects of Temperature Experimenters should place a thermographic sheet on test subjects hand Look for blue vein patterns Test subject should place fingers in a beaker of warm water for 1 minute (Do NOT get thermographic sheets wet) Observe color changes Test subject should place fingers in a beaker of cold water for 1 minute (Do NOT get thermographic sheets wet) Observe color changes Repeat this sequence 3 times
How did the color pattern change after the test subject’s fingers were placed in warm water? What caused this color change? How did the color pattern change after the test subject’s fingers were placed in warm water? What caused this color change?
Possible Variations Have students make temperature color sketches Have students make temperature data table Graph temperature data table to compare regions Have students design their own experiments to test temperature and/or gravity Test temperature and/or gravity in different regions of the body