Energy Balance Part B and Thermal Physiology Flashcards
general challenges of harsh temperatures (cold or hot)
1) freezing damage to cell membranes 2) chilling/heating damage to membranes 3) reaction rates will flucuate 4) extreme heat can result in water loss.
temperature is a measure of _____, which is:
temperature is a measure of heat, which is the kinetic energy of molecules.
the higher the temp, the ___ the reaction rates.
the faster the reaction rates, UP TO A POINT. high temps tend to be more trouble than low.
the ___ equation quantifies the effect of temperature on biochemical reaction rates. outine this reaction. What is the value for most biological reactions?
Arrhenius Van’t Hoff equation.
Q10= rate at temp/rate at temp-10degrees
Q10= (R2/R1)(10/T2-T1)
Usually, most biological reactions have a value of 2 or 3, meaning when the temperature is raised by 10 degrees, the reaction will double or triple
How does the arrhenius Vant Hoff equation apply to metabolic rate?
Q10= (Mr2-Mr1)(10/T2-t1)
How does the Q10 of a reaction or metabolic rate change at different temps?
Changes at high temps = effect on rate is large
changes at low temps= effect on rate is small.
Temperature of something is dependent on the amount of ___ contained per unit mass
amount of HEAT. (kinetic energy measure)
T/F: heat moves down thermal gradients
true. it radiates. it spreads to places with less kinetic energy
3 methods of heat gain
1) infrared radiation
2) conduction
3) metabolism
how can you gain heat from infrared radiation?
- obtained by solar or reflected energy. can also get it from atmospheric or radiant from surfaces( ex/ hot rock)
How can an animal gain heat from conduction?
direct contact with surface that is heated. ex/ snake on a warm rock
what is thermal conductivity?
how easily heat is con- ducted by the molecules of the substances. thermal conductivity of an object depends how well it can be used to “heat something up”
4 methods of heat loss
1) radiation
2) conduction
3) convection
4) evaporation
what is convection
Convection refers to the transfer of heat energy by cur rents of air or water (the medium).
warmer air is less dense than cool air, and thus the warm air will move up. and heat surfaces/ objects that are higher up.
forceful movements in the external medium, known as ___ _____, can carry heat away from a body
CONVECTION CURRENTS
forced vs free convection
In FREE convection, any fluid motion is caused by natural means such as the buoyancy effect, i.e. the rise of warmer fluid and fall the cooler fluid.
Whereas in forced convection, the fluid is forced to flow over a surface or in a tube by external means such as a pump or fan.
2 methods that hoary bats conserve heat
1) mother hoary bats roost on south-east side of trees. Allows them to heat up in the MORNING (sun rises in the east) when they do not have much energy and aren’t moving (therefore metabolism isn’t heating them much bc theyre nocturnal)
2) Hoary bats select trees in cluttered forest with open “pie wedge” on the southeast side. Preventing wind exposure
hoary bats thus save 1.24 kj/day of energy, which is about equivalent to saving 4 moths.
total body heat is the sum of: (3 factors), and is a balance between ___ ___ and ___
Total body heat = heat produced + heat gained from environment - heat lost.
It’s a balance between thermal conduction (how well the animal loses/gains heat by touching objects) vs insulation ( how well it can retain heat)
Why is evaporative heat loss so important when the ambient temperature is higher than the body temperature?
when Ta>tb, the heat will flow into the organism because of its thermal gradient. the animal is thus overheating. it is important that evaporative mechanisms are in place because heat cannot be lost through conduction/convection anymore.
because everything favors an increase in entropy, water from the organism (liquid state) will be vaporized into a gaseous state, increasing entropy and cooling the animal as it leaves the skin surface.
Homeotherms vs ploikotherms
poikilotherms (poikilos, “changeable”)— animals whose body temperatures vary with the environment. essentially an ectotherm
homeotherms—animals with narrowly varying body temperatures. essentially an endotherm
the more modern terms ectotherm and endotherm are descriptors of body temperature regulation based on :
the source of body heat.
heterothermic endotherm
animals that vary between self-regulating their body temperature, and allowing the surrounding environment to affect it. ex/ animals that can undergo torpor
ploikotherms are ectotherms which:
live in a thermally VARIABLE environment, such as aquatic environments. water has a high heat conductivity
what are regional heterotherms
endothermic animals that allow “parts” to go cold under extreme temperatures to preseve core heat (ex/ caribou, wolves)
what are temporal heterotherms
endothermic animals that let the whole body go cold. ex/ hummingbirds, mice, little brown bats
____ are changes in animal’s physiology due to new, naturally occurring environmental conditions
ACCLIMATIZATION. ex/ seasonal temp change
what is the dehnel effect?
type of acclimatization seen in small-bodied northern mammals. Results in an actual REDUCTION in body size and WHOLE ANIMAL BMR during the winter time.
What is acclimation? Adaptation?
acclimation are changes induced in the lab. ex/ manipuatlion of Ta and Tb in the lab.
adaptations are adjustment over evolutionary time
some ectotherms can compensate biochemically for changes in body temperatures to maintain a slight sort of internal temp. what is this called?
called metabolic compensation: acclimatization to temperature changes allows an animal to maintain a useful level activity. an animal’s metabolic reactions in cold temperatures are increased to a level that is closer to that of warm- acclimated animals even though their body temperatures are that of the environment’s.
4 ways ectotherms can metabolically compensate for fluctuations in body temperature (and ambient temperatures)
1) enzyme concentrations
2) homeoviscous membrane adaptation (cholesterol levels)
3) pH regulation (to maintain binding affinty of certain compounds)
4) isoform regulation.
explain metabolic compensation in alligators
This particular study ex-amined the activity levels of key enzymes in muscle tissue. Note that for Lactate DeHydrogenase, measured in the laboratory at 15, 22.5, and 30°C, the winter-acclimated animals have considerably higher enzyme activities at all measurement temperatures. This biochemical adjustment allows the cold-acclimated al- ligator to move better in the cold.
RMR? TNZ? TMR?
RMR= resting metabolic rate
TNZ= thermoneutral zone
TMR= torpid metabolic rate
Explain the BMR, RMR, TMR (TORPID MR) and TNZ in an endotherm. draw a graph. How can MR be measured in endotherms
metabolic rates can be measured via HEAT PRODUCTION. Torpid MR is generally lower than RMR and BMR because they are operating at a considerably lower temperature. RMR and BMR DECREASE and ambient temp INCREASES because the body does not ned to work as hard to maintain body temperature.
Heat loss can be calculated in terms of Q=C(Tb-Ta). What is C?
C= conductance, which is in the INVERSE of insulation. It measures the ability of a material to TRANSFER heat through conduction. therefore a person with lots of insulation is a bad conductor.
Recall that heatloss can be measured as Q= C(tb-ta)
HOw can you maintain a constant temp against a changing gradient? (ex/ Tb is constant while Ta changes).
C must DECREASE as Ta DECREASES. A person must then increase insulation if Ta increases because C is inversely proportional to I.
Heat production does not increase as Ta decreases and gradient increases, contant body temperature more due to the fact that there is increased insulation.
Explain how blood flow changes act as a method of thermoregulation
In a cold environment, blood can be diverted through shunts (anastomoses) deep under the skin to reduce heat loss.
If body heat needs to be released to the environment, or if external heat needs to be absorbed from a warm environment, vessels just under the skin surface can be opened.
