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Temperature Regulation. Definitions. Core Temperature Measured as oral, aural, or rectal temperature Temperature of deep tissues of the body Remains relatively constant ( 1 ºF or 0.6 ºC) unless a person develops a febrile condition
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Definitions • Core Temperature • Measured as oral, aural, or rectal temperature • Temperature of deep tissues of the body • Remains relatively constant (1ºF or 0.6ºC) unless a person develops a febrile condition • Nude person can maintain core temperature even when exposed to temperaturesas low as 55ºF or as high as 130ºF in dry air • Skin Temperature • Rises and falls with the temperature of the surroundings
Definitions • Core Temperature • Measured as oral, aural, or rectal temperature • Temperature of deep tissues of the body • Remains relatively constant (1ºF or 0.6ºC) unless a person develops a febrile condition • Nude person can maintain core temperature even when exposed to temperaturesas low as 55ºF or as high as 130ºF in dry air • Skin Temperature • Rises and falls with the temperature of the surroundings
Heat Production • Laws of Thermodynamics • Heat is a by-product of metabolism • Basal metabolic rate of all cells of the body • Effect of muscular activity on metabolic rate • Effect of endocrinology on metabolic rate (i.e., thyroxin, growth hormone, testosterone) • Effect of autonomic nervous system on metabolic rate
Heat Loss • How fast is heat transferred from deep tissues to the skin • How rapidly is heat transferred from the skin to the surrounding environment
How Fast Is Heat Transferred From Deep Tissues to Skin • Insulation Systems • Skin and subcutaneous tissue (i.e., fat) • Blood Flow • Cutaneous circulation
How Fast Is Heat Loss Fromthe Skin to the Surrounding Environment • Radiation • Conduction • Evaporation
Definitions • Radiation • Loss of heat by infrared heat rays (5-20m or 10-20X wavelength of visible light) • Conduction • Loss of heat from the body to a solid object • Evaporation • Loss of heat from the body through water vapor to the surrounding atmosphere • Convection • Effects of changes in the external environment (e.g., wind and water)
“Wind Chill Factor” • Effect of wind on skin temperature – temperature of calm air that would produce equivalent cooling of exposed skin • Cooling effect of air convection equals the square root of the wind velocity • For example, air temperature feels twice as cold at a wind velocity of 4 mph than if the wind velocity is 1 mph