Thermoregulation Flashcards
Temperature
Measurement of intensity of random motion of atoms or molecules; measurement of heat
Heat
Molecular kinetic energy; dependant on the number and speed of atoms
Conduction
Transfer of heat through a substance that is motionless down the temperature gradient; maximized by increasing the gradient difference
Convection
Heat transfer through substances with movement down the temperature gradient
Radiation
Transfer of electromagnetic radiation across a long distance with no direct contact between objects; maximized by increasing surface temperature
Evaporation
Energy required to change a liquid to a gas; a form of conduction
Heat storage
The smaller the surface area to volume ratio the slower heat is absorbed and dissapated; influenced by surface area, temperature gradient, and specific heat conductance
Poikilotherms
Body temperature fluctuates and is typically close to ambient
Homeotherms
Capable of maintaining a narrow body temperature range above or below ambient
Ectotherms
Rely on environmental heat sources
Endotherms
Generate heat through metabolism
Heterotherms
Capable of some metabolic heat production, but have a wide body temperature range; typically for torper or to conserve energy
Regional heterothermy
Maintaining some parts of the body endothermically but not the rest ex: birds do not warm their feet
Temporal heterothermy
Body temperature varies widely over time
Behavioral thermoregulators
Generating body heat through specific behaviors typically changing body shape or position to minimize wind or maximize sun such as reptiles basking or penguins huddling
Freeze tolerance
Coping with extensive freezing by allowing ice crystals to form in the body; thaw inside out and typically thaw heart last to prevent bursting
Freeze intolerance
Possessing some mechanism to prevent ice formation
Preemptive ice crystal formation
A form of Freeze tolerance in which extracellular fluid contains an ice nucleotide agent allowing ice crystals to form extracellularly but not intracellularly; solutes excluded from ice create a highly concentrated ecf drawing water from the icf which increases the concentration of the icf preventing freezing
Cryoprotectants
A mechanism of freeze tolerance which protect cells from injury during drastic temperature changes
Colligative cryoprotectants
Accumulate in high concentrations to raise the osmotic concentrations of body fluids which lowers the freezing points of the ecf which limits the amount of the total body that turns to extracellular ice ex: glycerol
Noncolligative cryoprotectants
Present in low concentrations that are typically membrane protectants; preserve subcellular structure from long term damage
Supercooling
A mechanism of freeze intolerant organisms in which a liquid is cooled below its freezing point without solidifying; typically used in low water organisms
Antifreezes
Lower the freezing point of the ecf
Antifreeze proteins
Mechanism in freeze intolerant organisms typically in polar fish; glycoproteins lower the temperature at which ice crystals enlarge, preventing the addition of water to existing ice crystals; noncolligative; typically only produced in winter because they are expensive
TNZ thermoneutral zone
Comfortable resting state for homeothermic organisms
UCT upper critical temperature
point at which an organism must begin cooling themselves
LCT lower critical temperature
point at which an organism must begin warming themselves
summit metabolic rate
highest metabolic rate at which an organism can warm itself without entering hypothermia
vasomotor response
selective vasoconstriction or vasodilation of blood vessels to the periphery prior to reaching LCT or UCT; constriction in the cold and dilation in the heat; ex: jackrabbits ears
shivering thermogenesis
chemical energy of muscles used for heat generation produced by antagonistic muscle groups; no work is generated energy is used for heat, energetically expensive
torper
allowing the metabolic rate and body temperature to drop closer to ambient to conserve energy; body temp is highly monitored to prevent freezing
non-shivering thermogenesis
brown fat oxidized to produce heat; highly vascular and rich in mitochondria; capable of quickly generating high amounts of heat; found most often in young mammals but never in birds
countercurrent heat exchange
heat moves by conduction from the arterial blood to the venous blood allowing blood to flow to extremities while keeping heat in the core
pilomotor muscles
muscles present in mammals or birds that can raise or lower feathers or hair to alter the thickness of the insulating layer
limited heterothermy
animals with a low surface area to mass ratio are more capable of tolerating higher temperatures; allow body temperature to drop especially at night and when water is scarce because evaporative cooling is not an option
gular fluttering
a type of active evaporative cooling used by birds in which they open their mouth and flutter a pouch
active evaporative cooling
sweating, panting, gular fluttering, saliva spreading
heat windows
specific areas on the body that permit heat loss from the body surface by radiation, convection or conduction; ex: rabbit ears
carotid rete
using nasal passages to cool blood moving to the brain to prevent overheating of the brain; often in conjunction with limited heterothermy
Hypothalmus
major thermoregulatory control center in the brain; the thermostat
