Lab Exam 2- Lab 9 Flashcards
thermoregulation
physiological or behavioral responses by which organisms regulate body temperature
organisms are classified as either
endotherms or ectotherms based on how they primarily regulate body tempertaure
endothermic species
mammals
warm their tissues from metabolic heat production
ectothermic species
reptiles and amphibians
depend on external environment for warming
what range in temperature causes fatal consequences
reductions of core body temp 10C
elevations of core body temp 5C
there is a thermal gradient from
deep body temp (core) to shell (skin) temperature
core temperature
temperature that is often measured by clinicians and researchers via rectal, oral, axillary, tympanic, or temporal temps or esophageal/GI temps
esophageal temperature
measured by inserting thermistor through the nose into the esophagus
GI temperature
measured using ingestible pill sensor
normal core body temperature
around 37C or 98.6F with variations in men and women
what causes variations in core body temp in men and women
circadian variation in men and women
menstrual phase in females
stage one hypothermia
at or below a core temp of 35C
signs of hypothermia
sever shivering, loss of limb movement, blueness of skin, confusion
what core body temp elicits a medical emergency
at or below 32C
causes hallucinations, delirium, and excessive sleepiness
what happens at core body temps 24-26
respiratory or cardiac arrest may occur
may become comatose
death
physiological responses to increases in core temp
increases in sweatrate, HR, and breathing rate
nausea, dizziness, weakness, and fainting may occur
what happens at core body temps that exceed 40C
heat exhaustion and heat stroke and death 45C
convection
body heat is lost to surrounding air, which becomes warmer, rises and is replaced with cooler air
radiation
body heat is lost to nearby objects without physically touching them
conduction
body heat is lost to nearby objects through direct physical touch
evaporation
body heat causes perspiration, which is lost from the body surface when changed from liquid to vapor
mechanisms of heat transfer
convection
conduction
radiation
evaporation
respiration
mechanisms of heat transfer during exercise are dependent on
external environment
if the environment is cooler than the body
heat will be lost from the body via radiation, conduction, and convection
as environmental temperature increases
heat loss via mechanisms decreases and the importance of evaporative heat loss increases
as environmental temperature exceeds body temperature
the thermal gradient for conduction, convection, and radiation is reversed and the body gains head through these mechanisms and EVAPORATION is the ONLY mechanism for heat loss
capacity for evaporative heat loss is affected by
the environment, primarily humidity and ambient temperature
as humidity and ambient temperature increase
the maximal capacity for evaporative heat loss decreases
when humidity is near 100% and ambient temperature is 30C +, what happens to evaporative heat loss
evaporative heat loss is minimal
wet bulb globe temperature (WBGT) index
tells us whether a given environment is safe or dangerous
includes measurements of air temp (Td), the temp of the wet bulb (Tw), and the temp of the black globe (Tg)
wet bulb globe temperature (WBGT) equation
WBGT= 0.7(Tw)+0.2(Tg)+0.1(Td)
Tw
the temperature of the wet bulb
influenced by level of humidity
Tg
temperature of black globe
measures radiant heat
Td
actual ambient air temperature
indicated by dry bulb
what happens to most energy transformation during metabolism
lost as heat
heat produced that is not lost is
stored in body tissues and will raise body temperature
body heat gain during exercise equation
heat produced - heat loss
specific heat of the body
amount of heat required to raise body temperature by 1C
specific heat in humans
0.83 kcal/kg body mass
heat required to raise body temp 1C equation
=0.83 (x) body mass
exercise does what to sweat rate
increases
effects of exercise and heat stress
exacerbates sweat loss
the increase in sweat rate and sweat loss during exercise results in
dehydration and reductions in plasma volume
dehydration
the loss of body water
changes in plasma volume are influenced by
alterations in total body water AND the distribution of water between intravascular, interstitial, and intercellular compartments
body water loss during exercise can occur through these four mechnisms
sweat loss
metabolic mass loss (MML)
respiratory water loss (RW)
urinary water loss (UWL)
sweat loss
responsible for most water loss
sometimes estimated from body mass alone (if a subject loses 1 kg of body mass for 1 hour of exercise they lost 1000 mL of sweat)
metabolic mass loss (MML)
results from O2/CO2 exchange
MML equation
VO2STPD x [((44*RER)-32)/22.4]
respiratory water loss (RWL)
results from ventilation
RWL equation
RWL= (0.019VO2STPD)(44-PH2O)
urinary water loss (UWL) equation
(urine volume/exercise duration)*density of water (1g/1mL)
sweat loss equation
sweat loss = total body mass loss - MML - RWL -UWL
heat stress effects on endurance performance
impairs endurance performance
@ a constant absolute intensity, time to exhaustion is shortened
race pace lowered in time trials
potential mechanisms that reduce performance in heat
high core and brain temps may reduce neuromuscular drive
attainment of core body temp ~40C results in central fatigue and impairments in performance
CV instability is the primary mechanism impairing endurance performance in the heat
heat stress elevates HR, decreases SV, leads to restrictions in plasma and blood volume
accelerated glycogenolysis and free radical production
main reduction in endurance performance under heat stress is due to
exercise duration
intensity
environmental conditions
heat acclimatization status
acclimatization
adaptations resulting from changes in the natural environment
acclimation
adaptations resulting from exposures produced in a controlled lab setting
how much time does it take for regular bouts of exercise in hot environment promote acclimation/acclimitization
7-14 days
physiological effects of heat acclimatization/acclimation
increase in plasma volume, earlier onset sweating, higher sweat rate, reduced salt loss in swear, reduced skin blood flow, and increased synthesis of HSP
which lead to reduced HR and lower core body temperature during exercise
effects of increase in plasma volume with acclimatization/acclimation
increases sweating capacity, SV, maintains blood volume, and allows body to store more heat without an increase in core temp
benefits of an earlier onset of sweating that comes with acclimation/acclimitization
allows the body to dissipate heat more quickly and reduce heat storage
benefits of reduced sodium loss in sweat during acclimation/acclimatization
minimizes the electrolyte loss that occurs during exercise
when are HSP synthesized
in response to stress and protect cells from heat damage
benefits of increased synthesis of HSP
increases stress protection to cells
procedure of lab
subject cycles for 40 minutes at workload near lactate threshold (~1-2.5 W/kg)
stopped when volitional fatigue or core body temp 39.5C
