W9.1 - Human Thermoregulatory Adaptation (Cold)

Question 1

What thermal stresses do Aboriginals in central Australia experience?

Answer 1

Heat stress during day

Moderate cold stress during night

Question 2

Describe temperatures in central Australia.

Answer 2

Summer: 22 - 37 deg
Winter: 4 - 21 deg

Question 3

What are clo units?

Answer 3

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)

Question 4

Describe reduction in heat conductance of Aboriginals at night in winter.

Answer 4

30% reduction in heat conductance from core to shell compared to white control subjects

Question 5

Describe metabolic heat production of Aboriginals ?

Answer 5

Lowered during night at winter

Question 6

What is impact of cold stress on Aboriginals?

Answer 6

Oppose cold stress by increasing insulation of body shell through vasoconstriction and by tolerating moderate hypothermia without metabolic compensation

Question 7

Describe Aboriginal cultural adaptations in cold weather.

Answer 7

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

Question 8

What is the cold exposure to Aboriginals during sleeping in winter?

Answer 8

Temperature is below thermoneutral temperature

No shivering, slept comfortably

Question 9

Describe sleeping temperature exposed to Lapp Shepherds from Norway.

Answer 9

Inside tent starts at comfortable level, by morning is same as outside (-25 to -30 deg C)

Question 10

How do Lapp Shepherds respond to cold stress?

Answer 10

Lower metabolic rate increase
Higher peripheral temperatures
Compared to white controls
1 deg greater drop in rectal temp

Question 11

Describe the housing that native Eskimos use.

Answer 11

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

Question 12

Describe Eskimo clothing.

Answer 12

Made of caribou
High quality insulation, light weight

Polar bear skin if caribou not available

Question 13

How insulative is Eskimo clothing?

Answer 13

3.5-6.5cm caribou fur = 7-12 clo units

266 - 456 cal/m2/hr insulative efficiency

Question 14

Describe metabolic rate of Eskimos.

Answer 14

13 - 45% higher than that of white controls

Question 15

Describe daily diet of Eskimos.

Answer 15

Protein 280g
Fat 135g
Carbs 54g

Question 16

What is the main source of Eskimos high metabolism?

Answer 16

High protein diet, but not the sole factor

Inland Eskimos have greater MR than coastal Eskimos (less cold stressed but same diet)

Question 17

Describe the impact of cold on bare hands of Eskimos.

Answer 17

10 deg C: Mild cold sensation only & Not signs of exhibiting pain

0 deg C: sustained exposure, white controls could not finish test

Question 18

Why do Eskimos have higher peripheral temperature?

Answer 18

Greater amounts of RBC, higher plasma volumes, more globulin proteins in plasma

Question 19

What maintains high peripheral temperature in Eskimos?

Answer 19

Enhanced vascularisation

Since incr in RBC requires greater vascular bed

Question 20

What temperature do oral temperatrures of Ama women divers fall to in dives?

Answer 20

33-35 deg C

Question 21

Describe the basal metabolic rate of Ama women compared to nondiving controls.

Answer 21

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

Question 22

At what temperature did Ama women start shivering when exposed to sequentially colder baths?

Answer 22

28.2 deg C compared to 29.9 deg C for controls

50% shivered at this point

Question 23

Describe impact of wearing wet suits on Ama women.

Answer 23

BMR did not show any seasonal changes

Cotton suit divers had seasonal changes in BMR

Question 24

Describe experiment setup for human thermoregulatory adaptation in cold enviroments.

Answer 24

Subjects sleeping overnight 8h in air temp of 3-5 deg C with insulation 0.29-0.34 clo

Question 25

What is 1 clo?

Answer 25

38 cal/m2/hr

Amount of insulation that allows a person at rest to maintain thermal equilibrium in environment at 21 deg C in normally ventilated room (0.1 m/s air)

Question 26

How do aborigines oppose cold stress?

Answer 26

Increasing insulation of body shell through vasoconstriction and by tolerating moderate hypothermia without metabolic compensation

Question 27

What cultural adaptations do Australian Aborigines have to manage cold nights?

Answer 27

Wear minimal clothing
During night, do not protect from cold air
Sleep on leeward side of windbreak between small fires
Cold exposure in sleeping microenvironment is below thermoneutral temperature
No shivering

Question 28

How do Norwegian Lapp shepherds respond to cold stress?

Answer 28

Lower metabolic rate increase and higher peripheral temperatures than white controls

Question 29

How can Eskimos’ cope with cold stress?

Answer 29

Increased metabolic rates, high peripheral temperatures, remarkable tolerance to cold exposure of extremities

Acquired during growth

Question 30

Describe change in BMR of Ama women in different seasons.

Answer 30

Lower BMR in summer, higher BMR in winter for Ama divers

Question 31

How did BMR vary with water temperature?

Answer 31

BMR varied as inverse function of water temperature at diving
BMRs of 35% above normal when water temp fell to 10 deg C

Question 32

Describe Ama divers shivering response.

Answer 32

Shivering threshold is lower allowing them to tolerate reduced core temperature without shivering

Question 33

Describe changes in skinfold thickness between Ama women from 1960-1980.

Answer 33

Divers and non-divers in 1980-82 were signifcantly fatter than those in 1960-61

Question 34

Describe shivering threshold of 1982 Ama divers and non divers

Answer 34

Shivered at same water temperature