Temperature Regulation

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 temperatures as 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 temperatures as low as 55ºF or as high as 130ºF in dry air

• Skin Temperature– Rises and falls with the temperature of the

surroundings

Basal Metabolic Rate

Metabolism Associated with Muscular Activity

Hormonal Effects on Metabolism

Insulation

Blood Flow

Radiation Conduction Evaporation

Heat Production Heat Loss

REGULATION OF BODY TEMPERATURE

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 From the 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

ºF = 35.74 + 0.6215T - 35.75V(100.16) + 0.4275V(100.16)