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Investigate the nature of heat loss in the human body.

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Heat Loss Aim The aim of the investigation is to investigate the nature of heat loss in the human body. This will be achieved by looking at the theory of Homeostasis, followed by conducting an experiment in relation to heat loss. * To determine the relationship between heat loss and body size. * To see if there is any correlation between heat loss, body size and insulation. The Nature Of Heat Loss Many processes both physical and biological are affected by body temperature. Enzymes work rapidly at optimum temperature (37 C) if the temperature alters they may become denatured. Cell membranes become more fragile as temperature rises. Diffusion rates increase by higher temperatures and decrease by lower temperatures. Liquids such as blood become more viscous as the temperature of the body falls. Most animals control their body temperature. Some are Ectotherms (outside heat), meaning they control their body temperature by their behaviour - a lizard gets heat from basking in the sun but when it is too hot it will seek shade to cool down. Homeostasis is the regulation of body temperature. Endotherm is the term used to describe this characteristic of mammals and birds. Humans maintain a relatively high and constant body temperature that enables active lives, even when their surrounding environment temperature is low. The body produces more or less heat depending on the rates of metabolic reactions. Homeostasis of body temperature can be maintained only if the rate of heat loss from the body equals the rate of heat production by metabolism. Heat Production Tissue respiration is the main source of heat in the body. Over 50% of the energy released in respiration is heat energy. The rate at which it is produced is proportional to the metabolic rate, which increases during exercise. Body Temperature Homeostasis Even though there are wide fluctuations in environmental temperatures, the homeostatic mechanism can still maintain a normal range for internal body temperature. ...read more.


Some adipose tissue is made up of brown fat. Brown fat cells contain many mitochondria and have a high metabolic rate. Babies and thin people have a relatively large amount of brown fat, whereas obese people tend to have little but extensive reserves of white fat. Sweat Evaporation of sweat from the skins surface is a means of increasing heat loss. When it is necessary to conserve heat, sweating stops. Autonomic nerves control the glands. These impulses come from the thermoregulation in the brain. If the body is sweating profusely heat cramps may occur. This is a result form the water and salt removal from the body. Salt loss causes painful contractions of the muscles- cramps, and in severe cases heat exhaustion can occur. To combat the body being to cold the body tries to conserve heat. This can include - * The body secretes the hormone adrenaline, which raises metabolic rate and increases heat production. * Shivering as muscular activity generates heat. * Adding layers of clothes to reduce heat loss, by convection trapping layers of hairs. * Eating more as eating stimulates heat production by respiration. * Food can also convert to subcutaneous fat for insulation. * Turning up the heating. To receive heat via convection. * Curl up in the foetal position to reduce the surface area. If the body's temperature falls below 24 C the heat mechanisms fail to work hypothermia can set in. Hypothermia is a lowering of core body temperature. Hypothermia affects cells in the brain and heart, leading to coma or death. Metabolism slows down and the muscles cannot work properly. Hypothermia is common in the elderly because they have reduced metabolic protection and perception against cold environments. To combat the body being too hot, the body tries to increase heat loss - * A hot person becomes lethargic and tends to lie down with their limbs spread out, this decreases heat production and increases heat loss. ...read more.


flask 31C 26.5C 15% 26C 18% 2000cm flask 11C 7.5C 32% 9C 19% Results In both experiments the heat was lost through convection, this was due to the hot water being in contact with the cooler air. The cooler air rises and then heats up drawing in more cool air to the hot water, the cool air keeps circulating until the water is cool. From the table above it is clear that the large flask conserves heat better than the smaller flask with or without insulation. It also shows that using insulation conserves the heat. When the bubble wrap was used, the larger flasks heat was conserved by 32%, the smaller flasks heat was conserved by 15 %. Bubble wrap is a good insulator as it has pockets of air, which heat doesn't flow through easily. Using the layers of nylon the heat was conserved by 19% in the large flask whereas the small flasks heat was conserved by 18%. Although both insulated, the flasks with bubble wrap appears to be the better insulator. These results can show that a bigger person wrapped up conserves heat better than a smaller person. It could also show that the smaller the creature the less important the type of insulation used. Evaluation Both experiments have been successful, however a few improvements could have been made. * Repeating the tests again, to gain stronger evidence of results. * Using temperature probes linked to a computer to record temperature, this would have achieved more accurate results. * Making sure the temperature was recorded accurately every minute. It could have been possible that the experimenter was taking longer to read the temperature at certain times during the experiment. * Stirring the water constantly to keep the temperature constant. * The temperature of the room could have varied, thus cooling the water quicker. By using these results and the knowledge of homeostasis it can be seen that body size and insulation play an important role in maintaining a stable body temperature. ...read more.

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