Lab 9 Flashcards
What is thermoregulation
Physiological or behavioral responses by which organisms regulate body temp
How do endothermic species warm their tissues
From metabolic heat production
How do ectothermic species warm their tissues
Using their external environment
Changes of what magnitude of core temp can be fatal
Reductions of 10°C or elevations of 5°C
What are 7 common measures of core temp
Rectal, oral, axillary, tympanic, temporal, esophageal, and gastrointestinal temps
How can gastrointestinal temp be measured
Using an ingestible pill sensor
How can esophageal temp be measured
By inserting a thermistor through the nose into the esophagus
What factors might cause small variations in core temp
Circadian variation (both males and females) and mestrual phase (females)
When does stage one hypothermia occur
At or below a core temp of 35°C (95°F)
When is core temp low enough to be a medical emergency and why
Core temp at or below 32°C can cause hallucinations, delirium, and excessive sleepiness
Which low temps can cause respiratory or cardiac arrest
24-26°C can cause this as well as comatose and death
What are physiological responses to increases in core temp
Increases in sweat rate, heart rate, and breathing rate
After initial physiological response to increased temp, what can happen if temps continue to rise
Nausea, dizziness, weakness, and fainting
When can heat exhaustion and heat stroke occur
At temps above 40° (104°F) with death often occuring at 45°C
Describe radiation as a means of heat transfer
Body heat lost to nearby objects without physically touching them
Describe convection as a means of heat transfer
Body heat lost to surrounding air, which becomes warmer, rises, and is replaced with cooler air
Describe evaporation as a means of heat transfer
Body heat causes perspiration, which is lost from the body surface when changed from liquid to vapor
Describe conduction as a means of heat transfer
Body heat is lost to nearby objects through direct physical touch
What is the only mechanism for heat loss at temps higher than body temp
Evaporation
What happens to maximal capacity for evaporative heat loss as humidity and ambient temp increase
It decreases
When does little-to-no evaporative heat loss occur
When humidity is near 100% and ambient temp is 30°C and over
What measurements are part of the Wet Bulb Globe Temperature (WBGT) test
Air temp (Td), temp of a wet bulb (Tw), and temp of a black globe (Tg)
What is the equation for the Wet Bulb Globe Temperature (WBGT) index
WBGT = 0.7 Tw + 0.2 Tg + 0.1 Td
What influences the temp of the wet bulb (Tw) in a WBGT test
Humidity
What does the black globe (Tg) measure in a WBGT test
Radiant heat
What does the dry bulb (Td) measure in a WBGT test
Actual ambient air temp
How is body temp raised
Using heat produced by the body that is not lost
What is the equation for body heat gain during exercise
Body heat gain = heat produced - heat loss
What is the specific heat in humans
0.83 kcal/kg body mass
What is the equation for heat needed to raise body temp 1°C (1kcal)
Heat required = 0.83 (kcal/kg) * body mass (kg)
What is dehydration
The loss of body water
What influences changes in plasma volume
Alterations in total body water and the distribution of water between intravascular, interstitial, and intercellular compartments
What are 4 primary mechanisms for body water loss during exercise
Sweat loss, metabolic mass loss (MML), respiratory water loss (RWL), and urinary water loss (RWL)
What is responsible fro the majority of body water loss during exercise
Sweat loss (estimated as body mass change following exercise if assumed to be the only mechanism)
If someone loses 1kg during exercise, what is their sweat loss
1000 mL
What is the density of water
1 g/mL
What is the molar mass of CO2
44 g/mol
What is the molar mass of O2
32 g/mol
What is the molar volume at STPD
22.4 L
What is the equation for sweat loss assuming it is not the only mechanism of body water loss
Sweat loss = total body mass loss - MML - RWL - UWL
How does heat affect time to exhaustion at a constant intensity
It reduces it by increasing fatigue
What are 5 theories for impaired performance in the heat
1) High core and brain temps may lower neuromuscular drive to reduce heat production and prevent high temps
2) Central fatigue at core temp ~40°C
3) Cardiovascular instability due to elevated HR, reduces SV, and thus reduced plasma and blood volume alongside a dramatic increase in skin blood flow
4) Glycogenolysis/hypoglycemia (controversial)
5) Increased free radical production
What are 4 factors influencing heat stress
Exercise duration, intensity, environmental conditions, , heat acclimatization, etc.
What is acclimatization
Adaptations resulting from changes in the natural environment
What is acclimation
Adaptations resulting from exposures produced in a controlled lab setting
How soon can heat acclimatization/acclimation be seen if exercising in regular bouts
7-14 days
What are 6 physiological modifications in heat acclimatization/acclimation
Increased plasma volume, earleir onset of sweating, higher sweat rate, reduced salt loss in sweat, reduced skin blood flow, and an increased synthesis of HSPs all lead to reduced HR and lower core temp
What does the increase in plasma volume as the result of heat acclimatization/acclimation do
Increase sweating capacity, increase SV, maintain blood volume, and allow body to store more heat without increasing core temp
What does the earlier onset of sweating as the result of heat acclimatization/acclimation do
Allow the body to dissipate heat more quickly and reduce heat storage
What does the reduced loss of sodium as the result of heat acclimatization/acclimation do
Minimize electrolyte loss
What does the increase in synthesis of HSPs do as the result of heat acclimatization/acclimation do
Increase the bodies stress protection to heat damage
How long with the subject in lab 9 (thermoregulation) be exercising for and at what intensity
40 mins at ~1-2.5 W/kg (near lactate threshold)
What 5 locations will skin temp be taken in the thermoregulation lab
Chest, posterior forearm, finger, thigh, and lateral calf
What 9 measurements will be taken at rest and during the last minute of each 5-minute window
RPE, thermal sensation, core temp, skin temp, HR, BP, VO2(STPD), VCO2(STPD), and VE(ATPS)
Why would exercise stop prior to 40 minutes during the thermoregulation lab
If the subject reaches volitional fatigue or if their core temp reaches 39.5°C
What 2 things does evaporation rate depend on
Temp and relative humidity and amount of skin surface exposed
What is the equivalent heat loss for 1 mL of sweat evaporated
0.58 kcal
What is Wet Bulb Globe Temperature (WBGT)
A composite temp that estimates effects of temp, humidity, and solar radiation on humans
What kind of dehydration can impair performance
Dehydration of 1-2% body weight
When are adaptations from heat acclimatization/acclimation lost
Within a few days of inactivity
