Temperature Regulation Prof K Sivapalan Body Temperature Body
Temperature Regulation Prof. K. Sivapalan
Body Temperature. • Body temperature of reptiles and lower animals is equal to environmental temperature – cold blooded animals. • Birds and above are warm blooded animals. The temperature is maintained within a narrow range, well above the environmental temperature. • Blood plays a vital role in transporting heat to minimize rising temperatures in heat gaining area of the body and lowering temperature in areas of heat loss. • As the heat exchange with environment occurs at the surface, the skin temperature can vary but the internal temperature is maintained constant. 24. 07. 05 Temperature regulation 2
Body Temperature measurement. • Body temperature is measured with clinical thermometer. Mercury, electronic and othermometers available. • Surface temperature: - axillary temperature is relatively constant and close to core temperature. • Core temperature is reliable and more constant. [oral, rectal and oesophagial]. • It shows very little change in gain or loss of heat. • The temperature increases towards the centre of the body • Range- morning oral temperature- 36. 3 -37. 1 • Diurnal variation of 0. 5 to 0. 7 24. 07. 05 Temperature regulation 3
Heat Exchange. Heat Loss: • Conduction. • Convection. • Radiation. • Evaporation: – Insensible perspiration 12 – 15 g/M 2/hr in environment less than 30 °C [skin- 50 %, RS 50%] – Sweat [perspiration] • Clothing, fan, application of cold water and warm water affect heat loss. • Heat gain: Metabolic and consumed heat. 24. 07. 05 Temperature regulation 4
Thermal balance. • Gain = loss. • Gain depends on metabolic needs and environment. • Loss depends on: – – fat insulation, clothing. Environmental temperature. Environmental humidity. Counter current mechanism of arteries and veins- central and surface veins in limbs. – Circulation to skin. 24. 07. 05 Temperature regulation 5
Regulation. • Centre- thermoregulatory centre in hypothalamus. • Sensors- hypothalamic cells, skin thermo receptors, others. • Efferents- sympathetics. 43° C 24°range. C • Effectors: within physiological – Cutaneous vessols. – Sweat glands. 24. 07. 05 Temperature regulation 6
Further Regulation • Extreme cold: Tone in skeletal muscles, Shivering, clothing, moving to hot place. • Extreme Heat: Fanning and moving to cool place. [risk of hypovoluemia] • Tissue damage beyond 18 and 45 °C • Failure of thermoregulation- 42 °C 24. 07. 05 Temperature regulation 7
Failure. 24. 07. 05 Temperature regulation 8
Effects of Alcohol. • Alcohol is a vaso dilator. • It dilates the cutaneous vessels. • It can lead to hypothemia in cold weather. 24. 07. 05 Temperature regulation 9
Fever. • Pyrogens reset themoregulatory centre. • The body reacts to the new set point. • This results in feeling cold and shivering, Skin blood flow reduces when fever starts. • Flushing and sweating occur when fever subsides. • Use of lukewarm water in hyperpyrexia facilitates evaporative heat loss by keeping the vessels dilated. 24. 07. 05 Temperature regulation 10
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