W9.1 - Human Thermoregulatory Adaptation (Cold) Flashcards
(34 cards)
What thermal stresses do Aboriginals in central Australia experience?
Heat stress during day
Moderate cold stress during night
Describe temperatures in central Australia.
Summer: 22 - 37 deg
Winter: 4 - 21 deg
What are clo units?
Amount of insulation that allows person at rest to maintain thermal equilibrium in environment at 21 degC in normally ventilated room (0.1 m/s air)
Describe reduction in heat conductance of Aboriginals at night in winter.
30% reduction in heat conductance from core to shell compared to white control subjects
Describe metabolic heat production of Aboriginals ?
Lowered during night at winter
What is impact of cold stress on Aboriginals?
Oppose cold stress by increasing insulation of body shell through vasoconstriction and by tolerating moderate hypothermia without metabolic compensation
Describe Aboriginal cultural adaptations in cold weather.
Wear minimal clothing
During night, no protection from cold air
Sleep on leeward side of windbreak between small fires
Do not attend to fire during night
What is the cold exposure to Aboriginals during sleeping in winter?
Temperature is below thermoneutral temperature
No shivering, slept comfortably
Describe sleeping temperature exposed to Lapp Shepherds from Norway.
Inside tent starts at comfortable level, by morning is same as outside (-25 to -30 deg C)
How do Lapp Shepherds respond to cold stress?
Lower metabolic rate increase
Higher peripheral temperatures
Compared to white controls
1 deg greater drop in rectal temp
Describe the housing that native Eskimos use.
Walls = whale rib rafters + double layer of seal skin with moss
Heat is at lower level than main floor, uses heat exchange
Indoor temps range between 10-21 deg C for coastal Eskimos, 0 deg C for Baffin island Eskimos
Describe Eskimo clothing.
Made of caribou
High quality insulation, light weight
Polar bear skin if caribou not available
How insulative is Eskimo clothing?
3.5-6.5cm caribou fur = 7-12 clo units
266 - 456 cal/m2/hr insulative efficiency
Describe metabolic rate of Eskimos.
13 - 45% higher than that of white controls
Describe daily diet of Eskimos.
Protein 280g
Fat 135g
Carbs 54g
What is the main source of Eskimos high metabolism?
High protein diet, but not the sole factor
Inland Eskimos have greater MR than coastal Eskimos (less cold stressed but same diet)
Describe the impact of cold on bare hands of Eskimos.
10 deg C: Mild cold sensation only & Not signs of exhibiting pain
0 deg C: sustained exposure, white controls could not finish test
Why do Eskimos have higher peripheral temperature?
Greater amounts of RBC, higher plasma volumes, more globulin proteins in plasma
What maintains high peripheral temperature in Eskimos?
Enhanced vascularisation
Since incr in RBC requires greater vascular bed
What temperature do oral temperatrures of Ama women divers fall to in dives?
33-35 deg C
Describe the basal metabolic rate of Ama women compared to nondiving controls.
BMR of Ama women was greater in winter compared to nondiving controls
Varied as inverse function of water temperature at diving
35% above normal when water temp fell to 10 deg C
At what temperature did Ama women start shivering when exposed to sequentially colder baths?
28.2 deg C compared to 29.9 deg C for controls
50% shivered at this point
Describe impact of wearing wet suits on Ama women.
BMR did not show any seasonal changes
Cotton suit divers had seasonal changes in BMR
Describe experiment setup for human thermoregulatory adaptation in cold enviroments.
Subjects sleeping overnight 8h in air temp of 3-5 deg C with insulation 0.29-0.34 clo
