15. Heat balance Flashcards
What are the three heat loss catagories? Explain them.
Conduction:
the transfer of thermal energy between neighboring molecules (in direct
contact): i.e. chair becomes
warmer when you sit on top of it.
Convection:
heat transfer occurring because of bulk motion (observable movement) of
fluids or gasses; warm air rises and cool air falls.
Radiation:
Thermal radiation is the process by which the surface of an object
radiates its thermal energy in the form of electromagnetic waves
(infrared).
Surface area of the body is related to … of heat
Volume of the body is related to the …. of heat
- Release
- Production
Heat produced by muscles =
Heat produced by blood =
Temperature difference skin + surroundings =
Choose:
Evaporation, Conduction, convection
Heat produced by muscles (solid): Conduction & blood (liquid): Convection
Temperature difference skin + surroundings = evaporation
What is the brody formula? What is it for? What part is metabolic weight?
H(kJ/day) = 400 * W^0.75
For calculating the amount of kJ needed for maintenance
W^0.75 = metabolic weight = weight corrected for non-metabolism tissues
Thumb rule for kJ produced with 1 liter O2 and 1 liter CO2?
1 liter O2 = 20 kJ, 1 liter CO2 = 25 kJ
Indirect vs direct calorimetry: what is measured?
direct = heat
Indirect = O2/CO2 ratio
How to know whether someone is burning Ch, protein or fat with indirect calorimetry?
Indirect calorimetry: can measure whether someone is using carbo or fat burning
(Ch = 1.0 RQ, Fat = 0.7, protein = 0.8) RQ (or: RER) = CO2/O2
ME from O2 and CO2 production = formula? (do not think you have to actually use it bc you know that 1 L O2 = 20 kj, 1 L CO2 = 25 kj
16O2(L) + 5CO2 (L) - 6 * N urine (however, N urine is often neglected)
What is a major advantage of indirect over direct calorimetry?
Direct = no movement
Indirect = movement, more information about daily variation in normal behaviour: free-living
Indirect calorimetry using DLW: concept?
Difference deterioration 2H and 18O is the amount of CO2 produced.
2H = lost only as H2O
18O is lost as H2O + CO2
What is summit metabolism?
In the cold, level of (maintenance) metabolism can be increased for longer time period
= Summit metabolism. Ca 5x maintenance (food intake compensate)
How can summit metabolism be reached?
- Uncoupling proteins (UCP’s)
Brown adipose tissue (UCP1)
Muscle + other tissues
Non-shivering thermogenesis: what do UCP’s do? What may UCP also be important for?
To maintain body temperature: non-shivering thermogenesis. UCP is a channel that can transport H+ gradient back over the membrane (so, without using ATPase). Energy = lost as heat.
They may also be important in body weight regulation. Without UCP, at 28*C mice become obese.
What is an alternative way for non-shivering thermogenesis, besides UCP’s?
in WAT, phosphocreatine-driven futile substrate cycling underlies heat release (non-shivering thermogenesis)
What happens to mice that do not have phosphocreatine-driven futile substrate cycling?
“Mice that do not have this creatine cycling are not able to maintain their body temperature”
