Thermoregulation

thermoregulation

maintenance and control of body temp under a wide range of environmental conditions

relative humidity

amount of moisture in the air relative to the capacity of the air to hold moisture at any given ambient temperature

heat index

a scale used to determine the risk of heat stress from measures of ambient temperature and relative humidity

wind chill index

a scale derived from the wind speed and the ambient temperature, and it reflects the temperature equivalent if wind were not a factor

heat stress

the physical work and environmental components that combine to create heat load on an individual

heat strain

The physiological responses and resulting thermoregulatory processes to combat heat stress

thermogenesis

body's production of heat; ingestion of food, muscle contraction, metabolism

radiant heat transfer

heat transferred via emission of electromagnetic heat waves

from the sun (radiation)

conduction

direct transfer of heat from one molecule in contact with another

convective heat transfer

movement of molecules in contact with another surface (skin)

evaporation

conversion of a liquid to a vapor

sweating

thermal balance

heat loss and production are in equilibrium

rectal temp

what is the gold standard for taking core temperature?

skin

____ temp is more variable than core temp due to exposure to environmental conditions

104

if body temp gets above ____ degrees problems will occur

thermal gradient

the difference in temp between 2 objects

heat loss is from the warmer of the 2

high

____ humidity decreases evaporative heat loss

air

____ movement increases convective heat loss

degree

the ____ of direct sunlight can add to radiant heat load

clothing

____ protects from heat loss but impairs heat dissipation by impairing convective heat loss

hypothalamus

____ is the primary integration center for control of body temp

warm

if someone has ____ skin their protective measures will occur sooner to decrease heat

increases

core temp ____ as exercise intensity increases

production > dissipation

production; dissipation

core temp is at steady state at workloads that are not as intense due to heat _____ and _____ being in equilibrium

lower

at ___ temps our body is more reliant on radiant and conductive heat loss

higher

at ____ temperatures our body is more reliant on evaporative heat loss (sweat)

decreases

if evaporative or radiant and conductive heat loss are impaired total heat loss ____ and heat storage is larger possibly moving us out of the safe range for our core body temp

lower

fit individuals start sweating at a ____ body temp

evaporation of sweat

what is the primary defense against heat stress?

factors influencing sweat rate

environmental conditions

exercise intensity

fitness level

degree of acclimatization

hydration status (dehydration= decreased sweating)

CV

____ challenges in hyperthermic conditions

- competition for BF between skin and working muscle

- vasodilation at skin level = decreased venous return = decreased SV = decreased Q

- sweating = decreased plasma volume = decreased SV = decreased Q

- vasodilation= decreased TPR = difficulty maintaining BP to perfuse organs

increased

similar Q during exercise in hot environment achieved by ____ HR

HR

during heavy exercise in the heat, ___ is no longer able to compensate for decline in SV, so Q is lower than during exercise in neutral temps

- causes decrease in performance

lower

individuals will have a ____ VO2max in hot environments

- lower Q

hot

in ____ environments

- BF to viscera decreases

- BF to heart, brain, etc. decreases

- BF to skin increases

acclimatization

the adaptive changes that occur when an individual undergoes prolonged or repeated exposure to a stressful environment

these changes reduce the physiological strain produced by such an environment

mechanisms of acclimatization

increased BV = increased Q and decreased HR

earlier onset of sweating to dissipate heat

increase sweating rate that can be maintained longer (because of increased blood plasma volume)

body composition

fat is an insulator

overweight individuals more susceptible to heat illness

females more susceptible than males (more body fat)

hydration

we should encourage ____ to maintain thermoregulation

electrolyte

endurance events may warrant ____ beverages over plain water

glucose and sodium will aid absorption than just plain water

EAH

Exercise-associated hyponatremia

low sodium due to excessive hydration (water intoxication)

- MEDICAL EMERGENCY

females

____ sweat less and have delated onset of sweating compared to the opposite sex

they also have a higher baseline core temp during luteal phase of menstrual cycle

children

_____ produce more heat, have greater surface area of skin, and less sensitive sweat glands so they don't tolerate high heat environments as well

need a longer and more gradual acclimatization period

older adults

____ ____ have decreased Q

greater exercise induced reductions in plasma volume and impaired dissipation of heat (higher risk for heat illness)

heat illness

a spectrum of disorders that range in intensity and severity from mild CV and CNS disruptions to severe cell damage including the brain, kidney, and liver

heat cramps

an acute disorder consisting of brief, recurrent, and excruciating pain in the voluntary muscles of the legs/arms/abdomen

heat syncope

a temporary disorder characterized by circulatory failure due to pooling of blood in the peripheral veins and the subsequent decrease in ventricular filling, which leads to a decrease in Q

exertional heat exhaustion

the inability to maintain adequate Q and an inability to maintain adequate moderate to high body temp

- body temp increases past safe range

exertional heat injury

A moderate to severe progressive multisystem disorder, with hyperthermia accompanied by organ damage or severe dysfunction

exertional heatstroke

a life-threatening illness characterized by high body temperature and central nervous system dysfunction

- can have organ damage

s/s of mild hyperthemia

faintness

dizziness

wobbly legs

stumbling gait

s/s of moderate hyperthermia

blurred vision, tunnel vision, blackout

collapse without loss of consciousness

s/s of severe hyperthemia

collapse- brief (< 3 min), loss of consciousness

sustained hypotension

shock, CV collapse

prevention of exertional heat illness

adequate time for acclimatization

exercise during cooler times

avoid exercise if heat stress index indicates high risk

adequate hydration prior to exercise and replace fluid during exercise

wear light color and loose-fitting clothing

hypothermia

a core temp less than 35 degrees C

a lowering of the body temp to a point that it affects normal function

frostbite

the consequence of water crystallization within tissues that causes cellular dehydration and leads to tissue destruction

prevention of cold induced injuries

appropriate clothing

warm up/cool down indoors

keep moving

hydrate appropriately

females

____ may tolerate the cold better

children

____ lose heat faster but vasoconstrict skin to compensate

cooler skin increases risk for frostbite

older adults

____ ___ are at the greatest risk of hypothermia due to blunted physiological and behavioral responses to cold (too late before they realize they are cold)

produce less heat

s/s of moderate hyperthermia

heat syncope