Temperature Regulation Flashcards
Conduction
Transfer of heat between 2 objects in physical contact.
Convection
Transfer of heat by fluid movement against an object.
Radiation
The transfer of heat by electromagnetic waves.
How much of water can be lost by sweating?
580cal/g.
What is the only method of heat transfer when TA>TB?
Sweating.
Thermoconformers
Organisms whose body temperature changes according to the external temperature, rather than carrying out thermoregulation so TB=TA.
Thermoregulators
Organisms that regulate their body temperature against thermal gradient, increase and decrease heat loss/production as required.
Warm-blooded animals
Their body temperature must be 18C above TA.
Cold-blooded animals
Body temperature is same as environment.
Poikilotherms
Organisms that cannot regulate body temperatures.
Homeotherms
Keep their body temperature constant.
Ectotherms
An animals that warms itself mainly by absorbing heat from its surroundings.
Endotherms
Animals that generate heat from metabolism.
Examples of poikilothermic ectotherms
Freshwater fish and some freshwater invertebrates.
Examples of homeothermic ectotherms
Marine invertebrates, polar marine fish and invertebrates.
Examples of homeothermic endotherms
Most land birds and mammals.
Where can ectotherms not live?
In extreme cold because metabolic rate would need to be too high.
What do ectotherms tolerate?
Wide internal variation but narrow environmental limits.
What do endotherms tolerate?
Narrow internal variation but wide environmental limits.
Catabolism
The breakdown of products releasing heat and energy.
Anabolism
Construction of molecules.
How can metabolism be measured?
Directly and indirect.
Direct calorimetry
Measurement of heat production as an indication of metabolic rate.
Indirect calorimetry
Metabolic rate, doubly-labelled water technique and respirometry.
Metabolic rate calculation
(Energy content of food- energy content of waste)/time.
Doubly-Labelled Water Technique
2H2 18O2 with 18O2 lost through metabolic CO2 and water loss while 2H is only lost in water with this ratio indicating metabolic rate.
Respirometry
Directly measure O2 consumption via a closed or open system.
Small animals metabolic rate
Fast MR/mass.
Large animals metabolic rate
Slow MR/mass.
What happens as mass increases?
Mass specific MR decreases rapidly.
Relative increase of surface area to mass
6(I^2/3)
Large animal heat
Heat up and cool down slow
Slow animal heat
Heat up and cool down quick.
Homogenous objects surface area relation to mass
log[S]=a+0.67log[m]. (S= Surface area, m=mass).
Isometry vs. Allometry
Isometry is proportional scaling while allometry is divergent.
Why is the coefficient not 0.67 in larger animals?
Thickening of bones and muscles decreasing surface area so coefficient is 0.63.
What is whole animal MR?
A power function of body mass.
Formulas for whole animal MR
MR= A x M^B or log MR= log[a] + b log[m] (where A= y-intercept of log-log plot, b is slope and m is mass).
Mass specific MR formulas
MR/m= A x M^(b-1) or log MR/m= log[a] + (b-1) log[m].
What is b in whole animal MR
0.75, showing MR does not scale with surface area.
Basal metabolic rate
The body’s resting rate of energy output.
Field metabolic rate
Rate of energy metabolism during normal activity.
Active Metabolic Rate
The total number of calories you burn in a day with exercise.
Maximum metabolic rate
Refers to the highest rate of ATP use for an organism.
Metabolic scope
Difference between basal metabolic rate and maximum metabolic rate.
Effect of temperature increase on metabolic rate
Increases reaction and metabolic rates.
Q10
Metabolic rate at a given temperature divided by rate at 10C lower.
What if Q10=1?
Then reaction is not temperature sensitive.
What if Q10=2 or 3?
Increased body temp increases reaction rate.
What group does environmental temp have most effect on?
Ectotherm.
Endotherm thermal neutral zone
A region of basal metabolic rate where temperature is maintained.
Acclimitisation
Process of gradual adaptation to a change in environment.
Acclimation
An organism’s change in response to a change in the lab.
Latitudinal gradient acclimitisation
Have a wide temperature gradient so acclimatisation maintains proper function.
Animal that has latitudinal gradient acclimitisation
Purple sea urchin inhabits nearshore marine environments from Alaska to Mexico.
Seasonal gradients
Stay in an area, so acclimatise to seasonal changes with an increased thermogenic capacity and cold hardiness.
Effect of winter on black capped chickadee
It triggers an increase in pectoralis muscle mass from 10-30%, with increased reliance on fats to fiel sustained shivering.
Effect of cold on frogs
When they acclimate from 25C to 5C oxygen consumption at all temperatures increases.
Phenotypic plasticity
The ability of an organism to change its phenotype in response to changes in the environment.
How is phenotypic plasticity captured?
In tolerance polygons.
(See Quizlet Image)
Goldfish area of tolerance polygon
1220.
Bullhead trout area of tolerance polygon
1162.
Habitats of high area tolerance polygons
Freshwater and widespread.
Habitats of low area tolerance polygons
Antarctic, marine and temperate.
Thermal gradient of enzyme function
Related to temperature experienced by animal in their natural habitat.
Thermo-adaptive LDH
0.22Km in all species at their optimal temperature.
Temperature impact on membrane
Increases temperature increases fluidity, while decreasing temperature decreases fluidity.
Lipid composition impact on membrane
Longer, saturated fatty acids are more rigid so can maintain function at higher temperatures while unsaturated fatty acids increase fluidity.
Cholesterol impact on membrane
It interacts weakly with nearby phospholipids, making membranes less fluid and more stronger.
Desaturases
Control double bond formation
Difference in goldfish membrane composition at 5C and at 25C
At 25C, phosphatidylcholine:ethanolamine ratio increases in favour of choline.
What phospholipid dominates in warmer environments?
Phosphatidylcholine.
What happens to 20C acclimated rainbow trout at 5C?
They acclimate with cholesterol and saturated fatty acids decreasing.
What happens to 5C acclimated rainbow trout at 25C?
They acclimate with cholesterol and saturated fatty acids increasing.
Heat shock protein induction
Temperature change.
What organisms produce more Hsp’s?
Organisms in warmer environments.
What do Hsp’s do?
Assist in folding denatured proteins to maintain their function at cost of ATP.
Intertidal species environment
Constantly changing so undergo more heat stress so have to produce more Hsp’s.
How is Hsp production triggered?
Unfolded protein is bound by a Hsp which was bound to a Hsf which is now able to enter the nucleus and increase transcription of Hsp genes so more are produced.
Hypothermia
When body temperature is below the thermal neutral zone.
Hyperthermia
When body temperature is above the thermal neutral zone.
Zone of metabolic regulation
Ambient temperatures below the lower critical temperature in which the animal may regulate its body temperature through changes in metabolic activity.
Zone of active heat dissipation
Temperatures above the thermal neutral zone in which the organism actively loses heat.
How effective is sweating?
Can improve heat loss by 20 times.
Difference in sweating in gender
Men sweat twice as much at same temperature.
Tropical acclimatisation of sweat
Increased sweating capacity and decreased salt content of sweat.
How much heat lost for 1g of water evaporated at 20C?
580cal.
How much does a person in a desert sweat?
1L/hr.
How can mammals cool down other than sweating?
Panting or licking fur.
How can birds cool down?
Oscillate floor of mouth and upper throat.
How do wood storks cool down?
Urinate on their legs.
How can camels prevent overheating?
It can vary body temperature by 6C.
Frostbite
Damage to the skin and tissues caused by extreme cold.
Three ectotherm strategies for surviving the cold
Selective extracellular freezing, antifreezes and supercooling.
Selective extracellular freezing
Encourages ice formation extracellularly by adding nucleating agents such as highly hydrophilic proteins.
Chironomid larvae at subzero temperatures
At -5C, 70% of body water is ice while at -15C 90% is ice.
Antifreezes
Lower freezing point to avoid ice formation and has protective action against freezing damage, with osmotic and protein antifreezes.
Osmotic antifreeze
Loss of water via osmotic action, typically involves glycerol, sorbitol and glycogen.
Protein antifreeze
Manufactured in liver and circulate around the body, bind to embryonic ice crystals and prevent further growth.
Example of a protein antifreeze
AFGP, 200x better than NaCl.
Supercooling
High pressure and/or lack of nucleating agents allow pure water to remain liquid to -20C.
Animals with supercooling
Frogs, spiders, insects and polar fish.
Issue with supercooling
Risk of rapid ice formation.
Mammal body temperature range
37-39C.
Bird body temperature range
39-41C.
Primitive mammal body temperature range
32-36C.
2 methods of keeping warm
Reduce heat loss and increase heat production.
Reducing heat loss methods
Can be postural (roll up) or behaviour (huddle) along with development of fat, fur and feathers to insulate.
Drawback of endotherms
Maintaining homeothermic state is metabolically expensive.
Shivering thermogenesis
Muscle action sees ATP hydrolysed to provide energy for contraction and chemical energy released as heat.
Non-shivering thermogenesis
Oxidisation of fats for heat.
What controls thermogenesis?
Noradrenaline from the hypothalamus.
Brown adipose tissue
Mammal specific with a scattered distribution, rich in mitochondria and thermogenin uncoupling protein.
When is brown adipose tissue at its highest?
In babies and in cold acclimatised adults.
2 types of thermoreceptor
Peripheral and central.
Peripheral thermoreceptor
Multimodal, in the skin, responds to temperature and touch.
Central thermoreceptor
Multimodal, in the CNS, responds to temperature and chemicals.
Location of thermoreceptors in insects
Antannae and feet.
Location of thermoreceptors in fish
Skin and PAH.
Location of thermoreceptors in reptiles
Facial pit.
Location of thermoreceptors in birds
Beak, tongue and nerve cord
Vampire bat thermoreception
Specialised IR receptors on its nose and a nucleus in the brain.
Pit viper thermoreception
Free nerve endings in facial pit, detect radiant heat, can respond to a 0.002C change and are directionally sensitive.
Mammalian thermoreceptors
React to relative changes.
Hypothalamus
10x sensitivity of peripheral thermoreceptors, act as a thermostat with the main sensor of temperature change.
Hypothalamus at normal temperature
Heat sensors inhibit cold effectors and cold sensors inhibit heat effectors so no effect.
Shunt vessels
Shunts blood away from skin in the cold to prevent heat loss or direct it to skin in heat to increase heat loss.
Heat production stats
56% from organs, 16% from brain.
Local regulation in extremities
Temperature allowed to change more than core temperature- local poikilothermy, also has shunt vessels and countercurrent exchange.
Countercurrent exchange
Allows for blood going to the extremities to transfer heat to the blood returning to prevent heat loss.
Porpoise flipper and rook limb countercurrent
Artery surrounded by veins allowing for more efficient heat transfer.
How do sauromalus reduce brain temperature?
Panting.
Dormancy characteristics
Lowered metabolic rate, changes in thermoregulation and lower food requirement.
Dormant states
Sleep, torpor, hibernation, winter sleep and aestivation.
Seal sleeping patterns
Sleep on ice for a few minutes at a time, rousing to check for predators.
Big cat sleeping patterns
Up to 20 hours a day.
Slow wave sleep
Associated with drop in hypothalamic sensitivity, reduction in core body temperature and change in cardiovascular and respiratory activity.
REM Sleep
Hypothalamic temperature control suspended.
Posterior nucleus
Thermal regulation (heat conservation) and sympathetic nervous system stimulation.
Anterior nucleus
Thermal regulation (heat dissipation) and parasympathetic nervous system stimulation.
Suprachiasmatic nucleus
Controls circadian rhythm.
What is cold skin temperature linked to?
Poor sleep.
Torpor
Lowered metabolic rate and body temperature, lasts for hours.
Rufus hummingbird torpor
Body temperature drops from 40C to 13C.
Awakening from torpor
Burst of metabolic activity to re-warm, but still cheaper than constant maintenance.
Hibernation
Allows animal survival when food is low or missing, entered through slow-wave sleep with periodic arousing for waste excretion, hypothalamic control lowered as much as 20C, TB can be as little as 1+TA.
What happens to CO2 in hibernation and hypothermia?
It drops.
Winter sleep
Characterised by small drop in TB and behavioural change such as curling up into a microhabitat.
Aestivation
The shutting down of metabolic processes during the summer in response to hot or dry conditions.
