Lab 9: Thermoregulation

Question 1

define thermoregulation

Answer 1

the physiological and behavioral responses by which organisms regulate body temperature

Question 2

how do endothermic species thermoregulate?

Answer 2

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

Question 3

how do ectothermic species thermoregulate?

Answer 3

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

Question 4

changes from normothermia that can be fatal

Answer 4

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

Question 5

difference between core temperature and shell temperature

Answer 5

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

Question 6

common measures of core temperature in a clinical setting

Answer 6

rectal, oral, axillary, tympanic or temporal temperatures

Question 7

common measures of core temperature in a research setting

Answer 7

(clinical setting sites) and also esophageal and gastrointestinal temperature

Question 8

how is esophageal temperature measured?

Answer 8

by inserting a thermistor through the nose into the esophagus

Question 9

how is gastrointestinal temperature measured?

Answer 9

using an ingestible pill sensor

Question 10

normal core temperature

Answer 10

37 degrees C (98.6 degrees F)

Question 11

factors that cause small variations in normal core temperature

Answer 11

circadian rhythm, menstrual phase in females

Question 12

when does stage 1 hypothermia occur?

Answer 12

at or below a core temp of 35 degrees C

Question 13

signs of hypothermia (stage 1)

Answer 13

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

Question 14

at what temperature is hypothermia deemed a medical emergency?

Answer 14

at or below 32 degrees C

Question 15

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

Answer 15

hallucinations, delirium, excessive sleepiness

Question 16

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

Answer 16

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

Question 17

physiological responses to increases in core temp

Answer 17

increases in sweat rate, heart rate, and breathing rate

Question 18

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

Answer 18

nausea, dizziness, weakness, and fainting

Question 19

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

Answer 19

temps exceeding 40 degrees C

Question 20

at what high core temp is death nearly certain?

Answer 20

45 degrees C

Question 21

what are mechanisms of heat transfer dependent on during exercise?

Answer 21

the external environment

Question 22

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

Answer 22

radiation, conduction, convection

Question 23

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

Answer 23

importance of evaporative heat loss increases

Question 24

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

Answer 24

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

Question 25

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

Answer 25

capacity of evaporative heat loss decreases

Question 26

at what humidity and temperature is evaporative heat loss minimal?

Answer 26

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

Question 27

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

Answer 27

if a given environment is safe/dangerous to exercise in

Question 28

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

Answer 28

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

Question 29

WBGT equation

Answer 29

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

Question 30

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

Answer 30

80% of energy transformation is lost as heat

Question 31

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

Answer 31

stored in body tissues and raises body temperature

Question 32

quantify the body heat gained during exercise

Answer 32

body heat gain during exercise = heat produced - heat loss

Question 33

what does specific heat of the body refer to?

Answer 33

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

Question 34

specific heat in humans

Answer 34

0.83 kcal/kg body mass

Question 35

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

Answer 35

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

Question 36

difference between dehydration and reduction in plasma volume

Answer 36

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

Question 37

4 primary mechanisms of body water loss during exercise

Answer 37

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

Question 38

primary mechanism for most water loss during exercise

Answer 38

sweat loss

Question 39

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

Answer 39

sweat loss is the only mechanism of water loss

Question 40

metabolic mass loss (MML) results from

Answer 40

O2/CO2 exchange

Question 41

respiratory water loss results from

Answer 41

ventilation

Question 42

how can MML, RWL, and UWL be calculated?

Answer 42

using formulas

Question 43

sweat loss =

Answer 43

total body mass loss - MML - RWL - UWL

Question 44

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

Answer 44

shortened

Question 45

factors influencing the reduction in performance under heat stress

Answer 45

duration, intensity, environmental conditions, heat acclimatization status

Question 46

potential mechanisms that reduce performance in heat

Answer 46

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

Question 47

difference between acclimatization and acclimation

Answer 47

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

Question 48

example of heat acclimatization

Answer 48

exercise in hot summer heat over several days

Question 49

example of acclimation

Answer 49

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

Question 50

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

Answer 50

7-14

Question 51

physiological adaptations of heat acclimatization/acclimation

Answer 51

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

Question 52

what do the physiological adaptations of heat acclimation lead to?

Answer 52

reduced heart rate and lower core temp during exercise

Question 53

how does an increase in plasma volume help with acclimation?

Answer 53

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

Question 54

how does earlier onset of sweating help during heat acclimation?

Answer 54

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

Question 55

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

Answer 55

minimizes the electrolyte loss

Question 56

purpose of heat shock proteins during heat acclimation?

Answer 56

protest cells from heat damage

Question 57

describe the procedure generally