Lect 24 Flashcards
normal core body temperature
37 C
heat exhaustion occurs at a core body temp of
39 C
describe the process of development of head exhaustion
- heat leads to excessive sweating + cutaneous arteriolar dilation -> hypovolemia
- hypovolemia -> decreased CO and decreased MAP -> circulatory shock
heat stroke develops at a core temperature of
41 C or above
process in which energetic particiles or energy or waves travel through a medium or space
radiation
the transfer of thermal energy through matter
conduction
the process of losing heat through the movement of air or water molecules across the skin
convection
water loss from respiratory passages and the surface of skin
evaporation
heat transfer from core comes from what two processes
- heat passively conduction to skin +
- heat convected by blood from core (majority)
what is the primary determinant of heat flow from core to skin?
the ability to alter skin blood flow
rate of heat loss from radiation: equation
= radiative heat transfer coefficient x (mean skin temp - radiant temp of another object) x body surface area
convective heat transfer coefficient is influenced by
air velocity
heat transfer coefficient is what in water compared to air
100 x greater in water
what process of heat loss becomes important when exposed to cold water
convection
equation for rate of heat loss by convection
= convective haet transfer coefficient x (mean skin temp - ambient temp) x body surface area
equation for rate of heat loss by evaporation
= evaporative heat transfer coefficient x (water vapor pressure of skin - water vapor pressure of environment) x body surface area
increased air velocity has what effect on vapor gradient
increases vapor gradient
What is the “central” coordinating center for temperature regulation
hypothalamus
- integrates information from skin and core receptors
What are skin receptors
- free nerve endings in the skin: both warm and cold receptors
- relay information to hypothalamus
local heating will produce local vasodilation and sweating caused by
- the local effect of temperature directly on the blood vessels and by local cord reflexes
local cooling will produce
local vasoconstriction
skin thermoreceptors change the of the response to signals from core thermoreceptors
sensitivity
intense aerobic exercise can theoretically increase core temp by
1 C every few minutes
What happens to CO when exercising in a hot vs cold environment
CO is reduced in a hot environment because blood is transfered away from core
What happens to HR when exercising in a hot vs cold environment
HR increases in a hot environment to compensate for reduced CO
what influence does training vs untrained individual have on skin blood flow and sweat rate
- greater skin blood flow
- sweat rate is greater in trained individual
heat acclimatization takes how long
a few days
what are the results of heat acclimatization?
- lowers HR
- threshold for cutaneous vasodilation is lower
- plasma volume increased
- increased sweat production
the effects of training and acclimatization on heat dissipation are
complementary!
fluid ingestion influences sweat rate and skin blood flow such that what happens to core body temperature
core body temperature is less in a person who drank fluid vs someone who did not
