Temperature Regulation Prof. K. Sivapalan
Temperature regulation 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
Body Temperature measurement. Body temperature is measured with clinical thermometer. Mercury, electronic and other thermometers 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
Temperature regulation Heat Exchange. Heat Loss: Conduction. Convection. Radiation. Evaporation: Insensible perspiration 12 – 15 g/M2/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
Temperature regulation 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
Temperature regulation Centre- thermoregulatory centre in hypothalamus. Sensors- hypothalamic cells, skin thermo receptors, others. Efferents- sympathetics. Effectors: within physiological range- Cutaneous vessols. Sweat glands. 43° C 24° C 24.07.05 Temperature regulation
Temperature regulation 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
Temperature regulation Failure. 24.07.05 Temperature regulation
Temperature regulation 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
Temperature regulation Fever. Pyrogens reset the 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