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What are two basic strategies used to generate heat for thermal regulation?
1. Futile cycling - Chemical potential energy is spent to generate heat.
2. Shivering thermogenesis - Heat production through uncoordinated stimulation of skeletal muscle contractile units
How do homeotherms regulate their body temperature?
- 1. Behavioral regulation
- 2. *Insulation
- 3. Coloration
- 4. *Regulation of heat loss by changing circulatory patterns
- 5. *Thermogenesis
What is a temperature coefficient (Q10)?
The relationship between a physiological rate and a 10C incremental change in temperature
What factors contribute to total thermal energy?
- 1. Metabolism
- 2. Conduction
- 3. Convection
- 4. Radiation
- 5. Evaporation
The transfer of thermal energy from one region of an object or fluid to another
The transfer of thermal energy between an object and an external fluid that is moving
The emission of electromagnetic energy from an object
When water molecules from the surface of an object absorb thermal energy from an object
Rate of heat exchange is higher with ______ surface area:volume ratio.
Rate of heat exchange is lower with ______ surface area:volume ratio.
Ratio increases as body size ____.
What is Bergmann's Rule?
Animals living in cold environments tend to be larger
What is Allen's Rule?
Animals in colder climates have smaller extremities
Ptiloerection and piloerection trap heat by
creating a stagnant air boundary around an animal, resisting heat transfer
How are enzymes modified in the short term with regard to changing temperature
1. Alter the "effective" concentration or activity of an enzyme
2. Modify substrate concentration
3. Change the energy supply for the reaction being catalyzed
4. Alter the intracellular environment to improve the enzyme's effects
How do enzymes acclimate/acclimatize with regard to changing temperature?
1. Alter the amount of protein (quantitative) - Increases as temperature decreases
2. Isoform switching (qualitative)
How have enzymes adapted to changing temperature
1. Alter the amount of constitutively expressed protein
2. Modify protein/enzyme structure for "optimal" function (alter km and/or kcat)
What is kcat?
Rate of substrate turnover
What is km?
Affinity for the substrate.
As km decreases, affinity increases
What are the three measurements of enzyme function that indicate how well suited an enzyme is to function at different temperatures?
1. Thermal stability
km is lowest for ____-adapted species
What are heat-shock proteins?
Molecular chaperones that catalyze protein folding and help refold denatured proteins
What is the heat shock response?
An increase in the levels of heat shock proteins in response to extreme temperatures
What is homeoviscous adaptation?
Membrane fluidity stays constant across large temperature changes.
As temperature decreases want ____ fluidity.
What influences thermal tolerance?
2. Length of exposure
3. Recent history
4. Evolutionary history (adaptation)
Why do animals succumb to cold?
1. Intracellular ice formation
2. Chemical reaction rates drop
3. CNS control, integration reduced
How do solutes influence the freezing point of water?
Higher solutes lower the freezing point
Marine invertebrates are ______. Do they freeze?
Isosmotic, freezing point equals that of seawater
Marine vertebrates are ______. Do they freeze?
Freshwater animals are ______. Do they freeze?
What are freeze avoidance strategies?
1. Lower freezing point by adding solutes
2. Elimination of ice nucleating sites
3. Produce antifreeze
What is supercooling?
The ability to remain unfrozen when body temperature drops below freezing point
Only occurs in deep water marine teleosts because won't encounter ice
What is the role of glycoproteins in preventing freezing?
Bind to ice crystals
Who tolerates freezing?
Thermoregulating below the TNZ is primarily achieved by:
2. Nonshivering thermogenesis
3. Allow portions of the body to cool (regional heterothermy)
Thermoregulating above the TNZ is primarily achieved by:
1. Active evaporative water loss
Thermoregulating within the TNZ is primarily achieved by:
2. Change in posture
3. Erection of insulation
4. Alter blood flow
A thermoregulatory strategy in which regions of an animal's body exhibit significantly different temperatures
Limit heat loss by letting appendages cool
Exacerbate heat loss by increasing blood flow to area
What are disadvantages of prolonged peripheral vasoconstriction?
1. Reduces gas exchange
2. Reduces waste removal
Where are countercurrent heat exchangers found?
The extremities of an animal
Ex: legs or flippers
What is the rete mirabile?
Complex of vessels that keeps the brain cool
Allows animals to tolerate adaptive hyperthermia in rest of the body
What is the function of nasal turbinate infolding?
Increases surface area, thus increasing contact with outside air, cooling blood
What are the advantages of regional endothermy in high performance fish?
- Increased aerobic metabolism = higher level of activity
- Increased nerve transmissions and visual acuity
- Warm stomach allows for fast digestion
- Freedom of movement through thermocline to chase prey
- Range expansion into polar waters