lab 9 Flashcards
Define thermoregulation
physiological or behavioral responses by which organisms regulate body temperature
organisms are categorized into what two categories and how are they divided
endotherms or ectotherms
- divided based on how they primarily regualte body temperature
Explain what endothermic species are
such as mammals, warm their tissues from metabolic heat production
Explain what ectothermic species are
such as reptiles and amphibians
* depend on the external environment for warming
deviations away from normothermia can lead to what
lead to physiological consequences
- decrease in core temp of 10 degrees C or elevations in core above 5 degrees C can be fatal
Where is the thermal gradient
from deep body temperature (core temperature) to the shell (skin) temperature
What is core temperature and what locations can you find them
temperature often measured by clinicians and researchers
- ie. oral, axillary, tympanic, rectal, temporal
- or esophageal and GI temp
How is esophageal temp measured
measured by inserting a thermometer through nose into esophagus
How is esophageal temp measured
measured using an ingestible pill sensor
What is normal core temperature
around 37 degrees C
- variations due to circadian veriation in male and female and menstrual phase in female
Stage one hypothermia occurs when?
at or below a core temp of 35 degrees C
At 32 degrees C what symptoms occur
hallucinations, delirium, excessive sleepiness
what are signs of hypothermia
shivering, loss of limb movement, blueness in the skin, confusion
At temp b/t 24 and 26 degrees C what can occur
respiratory or cardiac arrest may occur –> comatose or death
What is the physiological response to an increase in core temperature
increased sweatrate, HR, and breathing rate
- if continues to increase, nausea, dizziness, weakness, and fainting may occur
Heat exhaustion and and heat stroke may be observed in temps that exceed what
40 degrees C and higher and death certain at 45 degrees C
What is convection
body heat is lost to surrounding air, which becomes warmer, rises and is replaced with cooler air
What is radiation
body heat is lost to nearby objects without physically touching them
What is evaporation
body heat causes perspiration which is lost from the body surface when changed from liquid to vapor
What is conduction
body heat is lost to nearby objects though direct physical touch
If the environment is cooler than the body, heat will be lost from the body via what processes
radiation, conduction, and convection
as environmental temperature increases, heat loss via what decreases and the importance of what type of heat loss increases
radiation, conduction, and convection decrease but evaporative heat loss increases
As environmental temperature exceeds body temperature the thermal gradient for conduction, convection, and radiation does waht
is reversed and the body gains heat through these mechanisms
What is the only mechanism for heat loss
evaporation
the capacity for evaporative heat loss is affected by what
by the environment and primarily via humidity and ambient temperature
as humidity and ambient temperature increase the max capacity for evaporative heat loss increases or decreases
decreases
when humidity is near 100% and ambient temp is > 30 degrees C what happens to evaporative heat loss
evaporative heat loss is minimal
What is the Wet Bulb Globe Temperature (WBGT) index
whether a given environment is safe or dangerous
What is the equation for the Wet Bulb Globe Temperature index
WBGT = 0.7(Tw) + 0.2(Tg) + 0.1(Td)
What is Tw
temperature of the wet bulb which is influenced by the level of humidity
What is Tg
temperature of the black globe which measures radiant heat
What is Td
actual ambient air temperature indivated by the dry bulb
What happens to heat produced that is not lost
stored in body tissues and this will rise body temperature
what is the equation for body heat gain during exercise
heat produced - heat loss
What is specific heat of the body
amount of heat required to raise body temperature by 1 degrees C
What is the specific heat in humans
0.83 kcal/kg * body mass
What is the equation for heat requried to raise body temperature 1 decrees C (kcal)
(0.83 kcal/kg)(body mass (kg))
exercise and heat stress does what to sweat
- exercise increases sweat rate
- heat stress exacerbates sweat loss
with high sweating what happens to the body
cuases dehydration and reductions in plasma volume (NOT THE SAME)
changes in plasma volume are influenced by what
alteration in total body water AND distribution of water b/t intravasular, instersitital, and intercellular compartments
Body water loss during exercise can occur through what four primary mechanisms
- sweat loss
- metabolic mass loss (MML)
- respiratory water loss (RWL)
- urinary water loss (UWL)
sweat loss is equal to what
body mass change following exercise
if a subject loses 1 kg of body mass during 1 hr of exercise their sweat loss is estimated as what in mL
1000 ml (1g/mL)
For calculating sweat loss what do you need to keep constant
subject wearing dry clothing
is the assumption that sweat loss is the only mechanism of water loss correct
NO it is incorrect
What is metabolic mass loss (MML)
restulting from O2/CO2 exchange
What is the equation of metabolic mass loss
VO2STPD (L/min) * [((44 g/mol) * RER) - 32 g/mol) / 22.4 L]
What is the respiratory water loss (RWL) and what is the formula
resulting from ventilation
respiratory water loss = (0.019 * VO2STPD (L/min)) * (44-PH2O)
What is urinary water loss (UWL) formula
Urinary water loss (g/min) = (urine volume (mL) / exercise duration (min) ) * density of water 1g/1mL
What is the equation for sweat loss
Total body mass - MML - RWL - UWL
At a constant absolute intensity (a given cycling power output or running speed) what happens to exhaustion
time to exhaustion is shortened
What two things may reduce neuromuscular drive
- high core and potentially brain temperatures
- reduce metabolic heat production and potentially prevent excessively high temperatures
what is the primary mechanism impairing endurance training in the heat
cardiovascular instability
Heat does what to the cardiorespiratory system
increases HR, reduces SV, reduction in plasma and blood volume, and requires a dramatic increase in skin blood flow
what other mechanisms impair performance
- accelerated glycogenolysis –break down of glycogen into glucose
- increased free radical production
what is acclimatization
adaptations resulting from changes in the natural environment
what is acclimation
adaptations resulting from exposures produced in a controlled lab setting
Heat acclimatization/acclimation includes what symptoms
increase in plasma volume, earlier onset of sweating, higher sweat rate, reduced salt loss in sweat, reduced skin blood flow, and increased synthesis in heat shock proteins
the reduced loss of sodium is sweat that results from acclimatization and acclimation which does what?
minimizes the elecroyte loss that occurs during exercise
- HSPs synthesized in response to stress and protect cells from heat damage
what is the result with an increase in plasma volume that occurs with acclimatiztaion or acclimation
increases sweating capacity, increase SV, maintain blood volume, allows body to store more heat without an increase in core temperature
What happens to evaporative heat loss vs convective and radiative heat loss during exercise as the temperature increases
evaporative heat loss increases exponentially and convenctive and radiative heat loss decreases exponentially
What does the dry-bulb measure in the wet bulb/dry bulb thermometer
dry bulb measures temperature
the comparison between the wet and dry bulb termperatures gives you what
gives you the relative humitidy in the air
if a wet bulb and dry bulb displayed the same temperatures what you conclude about humitidy
there is 100% humidity
What happens to free radical production with heat-related exercise fatigue and why
increased free radical production = damage to muscle contractile protein
During a wet bulb globe tempreature it is used to estimate what
estimate the effect of temperature, humidity and solar radiation on humans
With a high brain temperature what is effected and why
neuromuscular drive = reduction in motor unit recruitment
What happens to muscle glycogen with heat-related exercise fatigue
accelerated muscle glycogen metabolism and hypoglycemia
dehydration of what % can impair performance
dehydration of 1-2% body weight
what are the 6 primary adaptations that occur as a result of heat acclimatization
- increased plasma volume
- earlier onset of sweating
- higher sweat rate
- reduced sodium chloride loss in sweat
- reduced skin blood flow
- increased heat shock proteins in tissues
