Thermoregulation Flashcards
When is body temperature the lowest and highest?
3-6 AM -1C
3-6 PM + .3-.5C
What percent of heat is lost via conduction?
3%
What percent of heat is lost via convection?
12%
What percent of heat is lost via radiation?
60%
What percent of heat is lost via evaporation?
25%
What is the heat balance equation?
(M-W) - (R+C+E) = S
Where is the thermoreceptor for blood located?
Hypothalamus
Where do peripheral receptors send signals to?
Hypothalamus
What systemic affects does the cold have?
Shivering, increased ventilation, increased HR, increased CO, vasoconstriction, increased BP, increased NE/T3
What systemic affects does heat have?
Sweating, vasodilation, increased HR, increased CO
How is a febrile condition induced?
Infection or pyrogen enters the body and macrophages recognize and release cytokines
Which cytokines come from macrophages and induce fever?
IL-1 IL-6
How do interleukins work?
Affecting hypothalamus and prostaglandin E2 change temperature resetting it to higher temperature
Why does shivering occur in febrile states?
Because your core temperature is at 37 and the hypothalamus has been set to a higher temperature so you shiver to increase body temperature
How do cytokines cause fever?
They cross the BBB and affect the OVLT endothelial cells to release PGE2 which affects the hypothalamus to increase the bodies normal temperature
At what temperature can the nervous system begin to be affected?
40C
What are the benefits of exercise?
Increasing the temperature by 10C increases enzyme activity 10x
Why does body heat increase quickly during exercise?
Because the mechanisms to get rid of excess heat are not present until the temperature gets higher
At rest which mechanism causes the most heat loss?
Radiation
In exercise which mechanism causes the most heat loss?
Evaporation
Why is it easier to run in cooler weather?
Because more blood can be sent to the SM instead of skin for heat loss
Why does heart rate increase over long periods of exercise?
Because decreased blood volume and decreased stroke output
At what point below normal body temperature does the body lose the ability to regulate temperature?
34.5C
What physiological changes occur with heat acclimization?
Blood volume increases (plasma volume) Sweat increases Cardiac output increases (increased SV) Heart rate decreases Core temperature decreases More blood to SM not skin
