Temperature 3 Flashcards
endothermy basics
- delicate balance of metabolic rate Mo2
- allows internal regulation of Tb
- has zone of thermoneutrality
metabolic heat and regulating Tb
- Tb regulated within 1C, and usually >Ta
- (Tb 32-43C in most vert)
- Heat is produced as waste of metabolism
- Mo2 therefore must be 10 fold higher than ectotherms
- must have insulation to prevent heat loss to keep Tb>Ta
HEATmetabolism=
-conduction+H-convection(together are usually minimized via insulation, tho variable between aquatic vs terrestrial)+radiation+evaporation (regulated for thermoregulation)
limitations of thermoregulation
near 0C and >40C regulation becomes difficult and hypo/hyperthermia occurs
metabolic responses to extreme Ta
-thermogenesis at low temp and active cooling at high temp, both costing higher metabolic rate
thermoneutral zone
- range of Ta where animal maintains Tb without changing basal metabolic rate
- Tb maintained via seasonal insulation like blubber, fur, or feathers, and behaviour like huddling and shelter
anatomical solutions to reduce heat loss: insulation
- minimizes surface area to volume (ie seals, whales, penguins)
- external insulation stabilizes air boundary layer
- Internal insulation: adipose/fat tissue increases conduction distance
- min. SA:Vol, and increased conduction distance via external/internal insulation minimizes heat conduction and radiation
anatomical external insulation
- stabilizes air boundary layer, even in water, by increasing conduction distance
- ie. hair, fur, feathers
- seasonal variations in thickness
physiological solutions to retain heat
- cool extremeties via vasoconstrictions and contercurrent exchange systems
- increased skin blood flow and evaporation
- ‘cool heads’
cool extremities/regional heterothermy
- reduce peripheral temperature to keep up core temperature of vital organs via:
a) vasoconstriction in skin, increasing conduction distance
b) countercurrent exchange so arterial blood conducts heat to cooled venous blood, returning some heat to the core
active cooling: increased skin blood flow
- ANS-mediated vasodilation response
- increased peripheral temperature
- reduced insulation
- more radiation/conduction
- pigmentation to increase light reflection
active cooling: increased evaporation
- sweating: hypothalamic control through symp nerves
- NaCl loss too
- acts as an acclimation to heat
- arterioles dilate and AV shunt constricts, forcing blood to move through skin for heat to convect out
- rapid shallow breating (panting) helps cool blood of moist respiratory membranes; no NaCl loss, requires skeletal muscle work
Cool heads
- found in savannah mammals: route carotid artery blood flow past nasal passages before blood reaches brain via nasal breathing (ie. reindeer or camels)
- moving air through nasal passage cools blood as it goes to the grain, or move air through mouth to keep blood warm in low Ta
Mechanisms for thermogenesis: increasing metabolic rate
- increased cell membrane ionic leakiness
- increased skeletal muscle activity
- shivering thermogenesis
- non-shivering thermogenesis
mech for thermogenesis/increasing metabolic rate: cell membrane ionic leakiness
- Na/K-ATPase has to work harder to maintain membrane potential
- being able to increase leakiness is one of the main differences between endotherms and ectortherms, as it allows thermogenesis
