Temperature Regulation

Tmb =

.33 Tsk + .67 Tcore

Tmb means

mean body temperature

Tsk means

skin temperature

Tcore means

core body temperature

temperatures that reflect core temperature

rectal T, tympanic T, right atrial T, esophageal T

sources of heat (can both get rid of and add heat)

metabolism, radiation, conduction, convection

Metabolism

splitting off phosphate, 70- 1000 kcal/hr

radiation

electromagnetic wave emission of a warm body to a cooler one; 60% of heat loss at rest

conduction

transfer between a solid object by direct contact

convection

transfer by virtue of the movement of air or liquid

evaporation

approx 25% of heat lost at rest; irreversible water loss; most important means of heat loss during exercise

sensible water loss

1.5L/day

which gland is responsible for sweating

eccrine gland

each g of H2O removes

0.58kcal as it is evaporated

increased humidity =

decrease in evaporation

thermal balance equation

heat storage = heat produced - heat dissipated

heat produced - heat dissipated

(M-W) +/- (Ra+Cd+Cv) - E

with exercise, there is low

radiative loss

sweating during exercise leads to

more evaporation

Tcore is related to

exercise intensity, not ambient T

rise in Tcore is not due to a

failure of heat loss mechanisms

the body has an elevated ____ ____ during exercise

set point, and it will vigorously defend it. Tcore temp will go up until it reaches homeostasis

at low environmental temperature, ___ proportion of heat loss by Ra, Cv, and ___ by E

greater; less; the body is hotter than the environment.

at higher environmental temperatures greater proportion of heat is lost by

evaporation; less by Ra, Cv

at environmental temperatures in excess of Tmb

evaporation is the only avenue for heat loss

heat transfer from core to skin is dependent on two factors

fixed, conductive component and variable convective component

fixed, conductive component

dependent on subcutaneous fat thickness; marked effect during cold water immersion

variable convective component

dependent on the level of skin blood flow; blood serves as a heat transfer medium to carry heat from the warm core to the cool skin

high level of skin blood flow causes

CV (cardiovascular) steal; vascular beds in the skin compete with the working muscle for part of the total Q

CV steal causes

increase in blood lactate and muscle glycogen utilization in the heat

fluid intake is essential to

maintain sweat rate; maintain blood volume (preserve heat transfer medium)

heat cramps

first sign of heat illness

heat exhaustion symptoms

headache, tingling sensations on arms and back, fatigue, rapid, weak pulse, pale moist cool skin, profuse sweating, chills or shivering

heat stroke symptoms (Tcore > 107 F)

headache, bizarre behavior or convulsions, loss of consciousness or coma, rapid full pulse, hot red skin, and sweating may or may not be present