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Enviro > Hot > Flashcards

Hot Flashcards

1
Q

Where are central warm receptors located?

A

Primarily in the hypothalamus but some in great vessels.

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2
Q

What is the upper degree of the TMZ?

A

31˚C

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3
Q

What causes ‘disturbance’’ to body at temperatures >31˚C?

A

Heat gain from environment and metabolic processes exceeds heat loss resulting in increased core temperature.

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4
Q

How much energy is used to transform water into water vapour (sweat stuff)?

A

2400kJ/litre

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5
Q

What is the most efficient mode of heat loss?

A

Evaporation

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6
Q

Clinical definition of hyperthermia?

A

Temperature of the body gets above 41 degrees (proteins will start to denature above this, thus can be fatal)

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7
Q

What are the two ways in which the body responds to high temperatures?

A

Increase heat loss

Decrease heat gain

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8
Q

What is the only way the body has to immediately decrease heat gain?

A

Behavioural Choices: reducing activity, Inertia, apathy, decrease skeletal muscle use.
Eat less

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9
Q

What is aestivation?

A

Some mammals reduce their activity to zero in the summer months & remain dormant in their burrows, thereby reducing the costs of staying cool. = reduces metabolic needs and BMR to survive heat with minimal food and work.

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10
Q

Which animals aestivate?

A

Bees, snails, crocodiles, frogs, snakes, lemurs, lungfish, cane toads

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11
Q

What physiological changes allow an animal to aestivate?

A
  • metabolic rate is reduced, water can be retained

- problem then is the buildup of nitrogenous waste

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12
Q

2 main mechanisms to increase heat loss

A

Evaporative cooling: (sweating and panting)

Peripheral vasodialtion

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13
Q

How are body shape and heat loss related?

A

Large surface area for low weight increases abilty of body to lose body heat via evaporative cooling.

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14
Q

What form of body heat loss does being leans specifically facillitate?

A

Conduction of heat from deep tissues to periphery (less distance to travel).

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15
Q

What are the two population of people Phil mentioned in relation to being really tall and living in a hot place?What is their average height?

A

Nilotic people of Sudan and the Masai of Kenya.

Average male 2.14m tall.

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16
Q

Average amount of sweat glands per cm2?

A

Total body averages 120 sweat glands per cm2 but this is not evenly distributed.

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17
Q

What % of sweat comes from glands on chest and back on humans?

A

50%

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18
Q

What is maximum sweat rate in man? What is this equivalent to in kj/hr and xBMR?

A

3L/hr but this is not sustainable.

7000kJ.hr
20x BMR

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19
Q

What is the average sweat rate for a man working in hot dry conditions per day?

A

12 litre/day.

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20
Q

Do men or women have higher average sweat rates?

A

Men

21
Q

Physiology of sweating:

A
  • SNS stimulation causes the eccrine sweat glands to secrete aqueous solution to the skins surface
  • There are also apocrine glands that are adrenergically innervated and secrete during excitement and anticipation
22
Q

Physiological difference between sweating at high an low rates (composition of sweat etc).

A
  • Sweating slowly will produce diluted sweat as there is more time for absorbtion of ions from sweat in the glands. Very hypotonic
  • Sweating profusely the secretion is much closer to isotonic as there isnt as much time for ions to move back into the glands.
23
Q

What is the main disadvantage of sweating and how can this be offset?

A

Loss of water and electrolytes.

Consume water with electrolytes lol

24
Q

What environmental factor grossly affects effectiveness of sweat? Why?

A

Humidity - The air is already somewhat saturated with water, thus it cant take more on and evaporative heat loss cant occur like usual.

25
Q

What feature of the body facilitates sweat use?

A

Hairlessness of body

26
Q

How long does it take for someone to fully acclimate to desert environments?

A

1-2 Weeks

27
Q

What does acclimation to a desert environment entail?

A

Increased sweat rate
Lower sweating threshold
Decrease in salt concentration in sweat

28
Q

What is hyperhydrosis? Cause?

A

Excessive sweating unrelated to heat or exercise.

Unknown cause but rumoured to be SNS activity. Can be triggered by some foods and medications.

29
Q

What was sweating sickness?

A

Random epidemic that occured in europe over the late 15th century

they had bad sweating symptoms which would lead to death within 3-18 hours.

cause is unknown, may be linked to bacterial infection as a result of poor sanitation.

30
Q

How do animals lose heat via evaporative cooling? How does this work?

A

Panting

Increase evaporation from upper respiratory tract.

31
Q

Advantages of panting over sweating?

A
  • Panting provides own air currents to facilitate evaporation
  • Does not result in loss of sodium in the way sweating does
32
Q

Disadvantages of panting over sweating?

A

Increased ventilation → Increases work of breathing and alkalosis.

33
Q

Underlying physiology of countercurrent heat exchanger?

A

The heat from warm arterial blood is passed onto the cooler venous blood (via conduction).

34
Q

Examples of countercurrent heat exchanger?

A
  • Testes
  • African Antelopes have them at the base of the brain and nasal passages to keep the brain cool
  • Seals, dolphins, whales all have heat exchangers on their fins (don’t have blubber on their fins, thus need it there)
  • Tuna (generate a lot of heat due to speed, thus have heat exchangers to cool them down)
35
Q

At what ºC does a camel start to thermoregulate to prevent hyperthermia?

A

41˚C

36
Q

At what ºC does a African gazelle start to thermoregulate to prevent hyperthermia?

A

46˚C

37
Q

How do camels cope with hyperthermia

A
  • Allow their body temp to increase during the day, have temperature gradients in nasal passages to protect the brain from overheating
  • store a lot of the heat they gain in the day in the fat in their humps then offload that during the night.
  • Camel urine really stinks as they have much longer loops of henle, thus they can concentrate their urine much better than we can.
38
Q

For a camel weighing 500kg, a rise in 4˚C corresponds to an increase in heat storage by …? This is the equivalent of saving how much sweat?

A

7000kJ

3L sweat

39
Q

Kangaroo rats and thermoregulation…

A
  • They do not drink water, instead get their water from O2 oxidation from food.
  • They store a lot of food in their burrows, the grains absorb some moisture from the atmosphere and then they eat them
40
Q

What are the three types of heat stress?

A

Heat stroke
Heat exhaustion
Heat collapse

41
Q

What is heat stroke?

A
  • Body overheating as a result of prolonged exposure to high temperature (exceeding 40 degrees core temperature)
  • Loss of thermoregulatory control → sweating starts to fail, thus decreases (very bad sign)
42
Q

Physiology and consequences of heat stroke:

A
  • Loss of sweating ability
  • Causes
    • Rising of core temperature
    • Denaturing of proteins
    • Destabilising of phospholipids and lipoproteins
    • CVS collapse
    • Can lead to a coma then death
43
Q

What is heat exhaustion?

A

Heavy sweating and elevated pulse as a result of overheating

44
Q

Physiology and consequences of heat exhaustion:

A

Effects the ECF volume which thereby affects ICF volume
Causes nausea and vomiting:
- Causes fatigue and weakness
- Poor mental function

45
Q

What is heat collapse?

A
  • loss of consciousness due to heat and humidity exposure

- fatigue and dizziness as a result of increased heat

46
Q

Physiology and consequences of heat collapse:

A
  • excessive sweating and shunting of blood to the skin leading to decreased BF to the brain
  • also if someone is standing their already impaired due to gravity → pooling of blood in the lower limbs
47
Q

What is malignant hyperthermia?

A

Severe reaction to anaesthetics.

Causes severe muscle contractions, high fever, elevated HR

48
Q

Physiology and consequences of malignant hyperthermia?

A
  • Ryanodine receptor in skeletal muscles is abnormal, interferes with calcium regulation
  • Treated using dantrolene
    • Medication stops release of calcium

Enviro (9 decks)

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