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Exercise Physiology > Lab 9: Thermoregulation > Flashcards

Lab 9: Thermoregulation Flashcards

1
Q

define thermoregulation

A

the physiological and behavioral responses by which organisms regulate body temperature

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2
Q

how do endothermic species thermoregulate?

A

endothermic species (mammals) warm their tissues from metabolic heat production

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3
Q

how do ectothermic species thermoregulate?

A

ectothermic species (reptiles & amphibians) depend on the external environment for warming

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4
Q

changes from normothermia that can be fatal

A

reductions in core temp of 10 degrees celsius or elevations in core temp of 5 degrees celsius

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5
Q

difference between core temperature and shell temperature

A

there is a thermal gradient from deep body temperature to skin temperature

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6
Q

common measures of core temperature in a clinical setting

A

rectal, oral, axillary, tympanic or temporal temperatures

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7
Q

common measures of core temperature in a research setting

A

(clinical setting sites) and also esophageal and gastrointestinal temperature

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8
Q

how is esophageal temperature measured?

A

by inserting a thermistor through the nose into the esophagus

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9
Q

how is gastrointestinal temperature measured?

A

using an ingestible pill sensor

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10
Q

normal core temperature

A

37 degrees C (98.6 degrees F)

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11
Q

factors that cause small variations in normal core temperature

A

circadian rhythm, menstrual phase in females

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12
Q

when does stage 1 hypothermia occur?

A

at or below a core temp of 35 degrees C

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13
Q

signs of hypothermia (stage 1)

A

shivering, loss of limb movement, blueness in the skin, confusion

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14
Q

at what temperature is hypothermia deemed a medical emergency?

A

at or below 32 degrees C

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15
Q

at or below 32 degrees celsius, what additional signs may present?

A

hallucinations, delirium, excessive sleepiness

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16
Q

what can happen at temps as low as 24-26 degrees C?

A

respiratory or cardiac arrest —> subject may become comatose and death usually follows

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17
Q

physiological responses to increases in core temp

A

increases in sweat rate, heart rate, and breathing rate

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18
Q

if core temp continues to increase without correction, what signs can present?

A

nausea, dizziness, weakness, and fainting

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19
Q

at what core temps do heat exhaustion and heat stroke occur?

A

temps exceeding 40 degrees C

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20
Q

at what high core temp is death nearly certain?

A

45 degrees C

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21
Q

what are mechanisms of heat transfer dependent on during exercise?

A

the external environment

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22
Q

mechanisms of heat loss from the body when the environment is cooler than the body

A

radiation, conduction, convection

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23
Q

change in mechanisms of heat loss from the body as environmental temperature increases

A

importance of evaporative heat loss increases

24
Q

once environmental temperature exceeds body temperature, what happens to the thermal gradient for conduction, convection, and radiation? how does the body lose heat?

A

the thermal gradient for these three is reversed and the body gains heat through these mechanisms; the ONLY mechanism for heat loss from the body is evaporation

25
Q

as humidity and ambient temperature increase, what happens to the capacity of evaporative heat loss?

A

capacity of evaporative heat loss decreases

26
Q

at what humidity and temperature is evaporative heat loss minimal?

A

humidity near 100% and ambient temp is 30 degrees C or above

27
Q

what does the Wet Bulb Globe Temperature (WBGT) index address?

A

if a given environment is safe/dangerous to exercise in

28
Q

what measurements does the WBGT index take into account? what are they each influenced by?

A

Tw (wet bulb temp): influenced by level of humidity
Tg (black globe temp): measures radiant heat
Td (dry bulb temp): actual ambient air temp

29
Q

WBGT equation

A

WBGT = 0.7(Tw) + 0.2(Tg) + 0.1(Td)

30
Q

what does an efficiency of 20% mean for a cyclist?

A

80% of energy transformation is lost as heat

31
Q

what happens to heat produced during metabolism that is not lost?

A

stored in body tissues and raises body temperature

32
Q

quantify the body heat gained during exercise

A

body heat gain during exercise = heat produced - heat loss

33
Q

what does specific heat of the body refer to?

A

the amount of heat required to raise body temp by 1 degree C

34
Q

specific heat in humans

A

0.83 kcal/kg body mass

35
Q

equation to find heat required to raise body temperature by 1 degree C

A

amount of heat (kcal) = 0.83 kcal/kg * body mass (kg)

36
Q

difference between dehydration and reduction in plasma volume

A

dehydration refers to the loss of body water, whereas changes in plasma volume are influenced by alterations in total body water AND the distribution of water between the intravascular, interstitial, and intercellular compartments

37
Q

4 primary mechanisms of body water loss during exercise

A

1) sweat loss
2) metabolic mass loss (MML)
3) respiratory water loss (RWL)
4) urinary water loss (UWL)

38
Q

primary mechanism for most water loss during exercise

A

sweat loss

39
Q

for body mass change following exercise to equal sweat loss, what assumption is made?

A

sweat loss is the only mechanism of water loss

40
Q

metabolic mass loss (MML) results from

A

O2/CO2 exchange

41
Q

respiratory water loss results from

A

ventilation

42
Q

how can MML, RWL, and UWL be calculated?

A

using formulas

43
Q

sweat loss =

A

total body mass loss - MML - RWL - UWL

44
Q

at a constant absolute intensity, time to exhaustion is ____ under heat stress

A

shortened

45
Q

factors influencing the reduction in performance under heat stress

A

duration, intensity, environmental conditions, heat acclimatization status

46
Q

potential mechanisms that reduce performance in heat

A

1) brain reduces neuromuscular drive at high core temps to reduce metabolic heat production and prevent excessively high temps
2) core temps above 40 degrees C cause central fatigue
3) cardiovascular instability (increased HR, decreased stroke volume, descreased blood volume, increase skin blood flow)
4) accelerated glycogenolysis and increased free radical production

47
Q

difference between acclimatization and acclimation

A

acclimatization refers to adaptions resulting from changes in the natural environment whereas acclimation refers to adaptations resulting from exposures produced in a controlled lab setting

48
Q

example of heat acclimatization

A

exercise in hot summer heat over several days

49
Q

example of acclimation

A

exercise performed in the lab under environmental conditions identical to the previous example

50
Q

regular bouts of exercise is a hot environment promote heat acclimatization/acclimation in ___ days

A

7-14

51
Q

physiological adaptations of heat acclimatization/acclimation

A

increased plasma volume, earlier onset of sweating, higher sweat rate, reduced salt loss in sweat, reduced skin blood flow, increased synthesis of heat shock proteins

52
Q

what do the physiological adaptations of heat acclimation lead to?

A

reduced heart rate and lower core temp during exercise

53
Q

how does an increase in plasma volume help with acclimation?

A

increases sweating capacity, increase stroke volume, maintains blood volume, and allows the body to store more heat without an increase in core temp

54
Q

how does earlier onset of sweating help during heat acclimation?

A

allows the body to dissipate heat more quickly and reduce heat storage

55
Q

how does reducing the amount of sodium lost help during heat acclimation?

A

minimizes the electrolyte loss

56
Q

purpose of heat shock proteins during heat acclimation?

A

protest cells from heat damage

57
Q

describe the procedure generally

A

Exercise Physiology (25 decks)

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