Thermoregulation

1. Temperature Regulation

2. 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

4. 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

6. 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

7. 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

8. 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

9. How Fast Is Heat Transferred
From Deep Tissues to Skin
• Insulation Systems
– Skin and subcutaneous tissue (i.e., fat)
• Blood Flow
– Cutaneous circulation

12. How Fast Is Heat Loss From the
Skin to the Surrounding
Environment
• Radiation
• Conduction
• Evaporation

13. Definitions
• Radiation
– Loss of heat by infrared heat rays (5-20m 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)

15. “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

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