Human Thermoregulation - the ability of an organism to keep its
body temperature within certain boundaries, even when the
surrounding temperature is very different
Skin
Helps with homeostasis- lose excess body
heat- vasodilation and sweating
Insulating layer (hair stands on
end when cold) trapping heat
Arterioles
Vasodilation
Vasoconstriction
Muscles
Shivering
Heat exchanged between the body and the environment
Heat Radiation
Covection
The factor determining the heat
transport process in the human body
The blood circulation system can transfer heat from one
part of the body to another by controlling the vessels
Conduction
Clothes which contain a lot of air and whose
material has a low thermal conductivity, are
good heat isolators
Evaporation
Other factors
Clothing worn (CLO)
Work/Activity
Metabolic heat production
Cold environments - Noakes 2000
(exercise and the cold)
What types of outcomes of the cold are possible (LAND)
Fatality (hypothermia), frostbite, reduced performance of the
muscles – combined effects of cold, wind and wet
Shivering (increased metabolic rate but also
increased vasodilation and blood flow and cooling)
Clothing can decrease the rate of temperature drop.
What types of outcomes of the
cold are possible (WATER)
Fatality (hypothermia), muscle cooling
(discomfort, potentially leading to drowning)
Cold shock response (very cold water at 10 degree C. Respiratory and musculoskeletal
response, hyperventilation, reduced duration of breath holding, disorientation and panic.
Shivering (increased metabolic rate but also
increased vasodilation and blood flow and cooling)
Different rates of cooling of skeletal muscles (dependent on body shape). Exercise can reduce the
insulating capacity of muscles in the water. Potentially greatest muscle cooling in the arms and can
inhibit the ability to swim and keep the head above the water. Variations in advice for survival.
Clothing can affect the
rate of temperature drop.
Measurements
Body shape
Clothing
Distance and time
Body temperature, air
temperature, wind speed,
humidity, water temperature