Lecture Ten - Body temperature

Question 1

How do higher temperatures generally effect metabolic rate?

Answer 1

Generally higher temperatures increase metabolic rate.

Question 2

What is Q10?

Answer 2

Measure of increase in rate of any process with a 10 degree C temperature increase.
If the rate doubles, Q10 = 2.
If the rate triples, Q10 = 3, etc.
May be rate of chemical reaction, diffusion, metabolism, etc.
Major consequences for animals.

Question 3

What is the optimal temperature range?

Answer 3

Thermoneural zone.
Most energetically efficient temperature.
Differs by animal groups.
Determines environmental tolerance.
If you get outside the optimum, metabolic rate must increase to counter this.

Question 4

How can animals exchange heat with the environment?

Answer 4

Conduction - Direct transfer of thermal energy at rate dependant on conductivity.
Convection - Transfer of thermal energy by movement of air or liquid.
Radiation - Indirect heat transfer between objects E.g. sun warmth.
Evaporation - Removal of heat by liquid losing molecules of gas, occurs mainly though skin and respiratory surfaces.

Question 5

What are exotherms and endotherms?

Answer 5

Ectotherm = Outside source of heat. Have a low metabolic rate, the environmental temperature determines their body temperature.
Reduced expenditure on thermoregulation.
Limited duration of activity.
Reliance on external heat sources.

Endotherm = Generate their own heat inside. Have a high metabolic rate which largely determines their body temperature.
Endotherms tend to have a higher body temperature, as metabolic activity produces heat as a byproduct.
Endotherms on average have ‘leakier’ membranes.
Need to maintain concentration gradients of ions across the cell membranes.
Need to maintain proton gradients across mitochondrial membranes.
Greater environmental range.
Greater energy cost of living.

Question 6

What are poikilothermic and homeothermic organisms?

Answer 6

Poikilothermic = variable body temperature (both endotherms and ectotherms can be this). 
Homeothermic = body temperature is constant (both endotherms and ectotherms can be this).

Question 7

What does terminal heterothermy and regional heterothermy mean?

Answer 7

Terminal heterothermy = differing temperature over time.

Regional heterothermy = differing temperature throughout the body. E.g. higher temperature around organs.

Question 8

How can body temperature be regulated?

Answer 8

Morphology.

Physiological  and behavioural changes can be made though general adjustment in: 
Rate of heat exchange. 
Evaporative heat loss. 
Behaviour. 
Metabolic heat production.

Question 9

What are countercurrent and concurrent heat exchanges?

Answer 9

Countercurrent heat exchange involves blood vessels containing warmer blood flowing away from the heart and organs being cooled by cooler blood flowing from the extremities back to the heart.
This limits the amount of heat lost when blood flows in the extremities.
Concurrent heat exchange is when blood flows in the same direction in neighbouring blood vessels.

Question 10

How does heat loss by evaporation work?

Answer 10

Only works when the air is not saturated (when its not humid).
Evaporation of sweat or other liquid.

Question 11

How does body temperature vary between vertebrates?

Answer 11

Range of body temperatures through different taxa.

Generally, the bigger the animal, the higher the core body temperature.

Question 12

How does shivering and non-shivering thermogenesis work?

Answer 12

Shivering:
Occurs in muscles.
Contraction.
ATP to ADP = releases heat.

Non-shivering thermogenesis:
Brown adipose tissue: thermogenin (protein) uncouples movement of protons across membrane from ATP protein.
Produces heat but not ATP.