Cardiovascular and respiratory control: acclimatisation and fever

Question 1

Acclimatisation

Answer 1

Individual response to environmental change

Question 2

Adaptation

Answer 2

Traits heritable through generations

Question 3

Peripheral cold injury

Answer 3

Trench food

Frost bite

Question 4

Trench foot

Answer 4

When soldiers who fought in soggy trenches during WWI.

Caused by the cooling of peripheral nerve and muscle, which then caused sensory and motor malfunction

Question 5

Frostbite

Answer 5

Results from freezing of tissue. Can lose finger tips and toes etc

Question 6

You’re not dead until you’re warm - why and how

Answer 6

Immersion in cold water with high thermal conductivity can lead to hypothermia but subcutaneous fat will provide something insulation.
Woman trapped under ice I’m freezing water for 80 minutes
After 40 minutes: cardiopulmonary arrest
After 80 minutes was recused: treated with cardiopulmonary I pass amd axtracoeal blood warming
After 4 hours: heart started to beat again and made a nearly full recovery

Why? At freezing temperatures, cellular oxygen demand was reduced so much that cells could survive without effective circulation

Question 7

Surgically induced hypothermia

Answer 7

May provide benefits that outweigh risks

• neurosurgery on inaccessible aneurysm: body can be cooled by extracorpeal circulation so that blood flow is stopped for ~15minutes
• cardiac surgery e.g valve replacement cold cardioplegia is used to stop heart for ~60 minutes

Question 8

what groups of people show adaptations to prolonged cold exposure

Answer 8

aborigines and inuits

Question 9

How did aborigines adapt to prolonged cold exposure

Answer 9

• nomads that lived outside and wore no clothing
• very cold temperatures at night
• normally, people shiver to maintain core temp
  BUT shivering keeps you awake
• aborigines have reduce shivering and their core temperature will drop, but they sleep well

Question 10

pros and cons of vasoconstriction for thermoregulation

Answer 10

helps maintain core temp

but causes problems such as loss of manual dexterity and frostbit

Question 11

how is manual dexterity improved and risk of frost bite reduced?

Answer 11

paradoxical vasodilation
- blood flow and skin temp show a hunting reaction
well developed in inuits

Question 12

who has developed hunting reaction

Answer 12

inuits

Question 13

what shows hunting reaction

Answer 13

subject finger immersed in ice water for prolonged time.
will vasocontrict to maintain core temp then paradoxically dilate to provide protective effects.
Finger temperature shows oscillations as changes from contraction to dilation

Question 14

what causes adaptation to prolonged cold exposure

Answer 14

though to be combination of genetic adaptation and acclimatisation

Question 15

pros and cons of involuntary muscle activity

Answer 15

can increase heat production x 5 briefly, but raises convective heat loss

Question 16

when does vasoconstriction of skin vessels mostly occur

Answer 16

in the TZ

main response to cold exposure

Question 17

increase heat production mechanisms

Answer 17

• voluntary muscle activity
• involuntary muscle activity
• brown fat metabolism

Question 18

decreased heat loss mechanisms

Answer 18

• behavioural (heating, clothes)
• vasoconstriction of skin vessels
• horripilation

Question 19

acclimatisation to prolonged heat exposure

Answer 19

within 7 days:

• sweat and evaporation capacity increased
• salt loss during sweating is reduced to 20% of initial value

Question 20

physiological changes to continued heat exposure

Answer 20

• rectal temp increases initially, then after 9 days reduces close to normal
• HR increase initially, then after 9 days reduces close to normal
• sweating increases rapidly across 9 days

Question 21

increased heat loss mechanisms

Answer 21

• behavioural
• vasodilation of skin vessels
• sweating

Question 22

reduced heat producton

Answer 22

• inactivity, inertia

- anorexia - high water content foods are preferred

Question 23

Fever

Answer 23

mild to modest elevation in body temp
37.5-40 degrees C
common sign of infection

Question 24

what happens to set point during fever

Answer 24

• body tried to maintain original set point and so patient feels cold
• Body then achieves set point and so doesn’t feel cold

Question 25

symptoms of hyperthermia

Answer 25

heat syncope
heat exhaustion
heat stroke

Question 26

heat syncope

Answer 26

fainting due to vasodilation and fall in BP

Question 27

heat exhaustion

Answer 27

water & salt deficiency due to prolonged sweating

Question 28

heat stroke

Answer 28

loss of thermoregulatory control as brain temp rises and function fails - usually fatal

Question 29

Malignant hypothermia

Answer 29

triggered by drugs
2,4DNP originally an explosive then reintroduces to stimulate metabolism and promote weightloss

DNP is now banned

Question 30

thermoregulation in elderly

Answer 30

• physiologically less efficient
• mobility greatly reduced and so is shivering and vasoconstriction in response to cold
• heat-producing lean body mass diminishes
• financial difficulties keeping heating off in winter
• in the heat elderly show reduced sweating and vasodilation

Question 31

thermoregulation in neonates

Answer 31

• linear VS area VS volume change
• heat loss is proportional to surface area
• heat production is proportional to volume

neonates have a greater surface area to volume ratio than adults =
produce relatively little heat but lose relatively more

• neonates are prone to drop in core temp in response to cold stimuli
• they can vasoconstrict and vosodilate skin blood vessels and they can sweat