Thermoregulation Flashcards
Heat production =
&
Heat transfer =
A. Thermogenesis
B. Thermoconductance
Behavioural mechanisms
- Heat production - exercise
- Heat transfer - basking, retreating, posture
Physiological mechanisms
-Heat production
Increase metabolic rate
Shivering thermogenesis
Non shivering thermogenesis (mammal specific)
-Heat transfer
- Control of peripheral blood flow
- activation of piloerector muscles (increase thickness of pillage)
- Sweating and panting (evaporative cooling)
Potential environmental factors which might affect thermal regulation of an animal in an environment like the below
Types of Animal Thermoregulation
Poikilotherm:
Homeotherms
- Ectotherms:
- Endotherms:
Poikilotherms - Body temp varies with the environemtnal temp (fish/lizards)
Homeotherm - Body temp stays constant (Mammals/Bird)
Ectotherm - Rely on external environmental heating as the metabolic heat production is low.
Endotherm - High metabolic heat production and less reliant on environmental heat to raise body temp
Familiarise
Example of thermoreg fish
Antartic fish
Stable -1.8oC year round
“Homeothermic ectotherm, very stable bod temp but still ectothermic, can’t generate its own heat (Not that Antartica has alot of heat at all!) Thats what warms the body and stops it freezing) Because environment is stable, they have a -1.8oC year round”
(Stable body temp but relying on external heat)
Leatherback turtles can maintain bod temp ____ ______ than sea surrounding them.
Leatherback turtles can maintain bod temp 18oC higher than sea surrounding them
Homeothermic/Poikilothermic endotherms =
A Mesotherm
Galapagos marine iguanas are a
poikilothermic/homeothermic ectotherm
expalin how?
- Cold sea temp but warm terrestrial environment
- reduce heat loss during dive by peripheral vasoconstriction and bradycardia
-Increase heat gain after dive by peripheral vasodilation and tachycardia
Familiarise
- On land = tachycardia + peripheral vasocardia = to warm body
- Diving = bradycardia + peripheral vaso constriction = retains heat around core/vital organs
Whales and Dolphins
-homeothermic endotherms
educe heat loss in water by high metabolic rate and low thermal conductance (thick blubber layer)
- control thermal conductance by controlling peripheral blood flow (shunt vessels)
- reduce heat loss from fins by countercurrent blood flow in fins using rete systems
Naked mole rat
-mammal (cold blooded)
truly poikilothermic (no ability to regulate body temp)
body temp vs amient temp
Main thermoregulatory organ…
Hypothalamus (key regulatory organ)
-specific neurons respond to either increases or decreases in temperature by altering action potential discharge rate. The combined action of both groups results in a temperature set point.
-
When are thermoregulatory responses stimulated?
When the body temp is outside the thermoneutral zone.
TNZ for a naked human male is 25-30
(thermo neutral zone)
What is Shivering thermogenesis?
A thermoregulatory response which activates heat in the muscles.
What is Non-shivering thermogenesis?
Specialised tissue (brown fat) contains huge quantities of mitochondria.
Increased metabolic work in this tissue is stimulated by sympathetic innervation. The normal biochemistry of metabolism is altered so that heat can be produced without the production of ATP.
Pyrogens - Fever inducing substances after the hypothalamic temperature set point.
What is behavioural thermoregulation?
-Herding
emperor penguins - chicks and adults huddle together
honey bee swarm density depends on temp
(clump together and shiver wing muscles to maintain heat, when warm they disperse more to allow air flow through the swarm)
-Posture
Polar bears and wind chill
(like a dog when warm or cold / splay or curl up tuck nose in)
ground squirrels use their tails as an umbrella
antelope turn to face to or away from the sun
Physiological thermoregulation
Radiators - Increased heat loss from body radiators e.g. rabbits and elephant ears (good at losing heat, elephants cover ears with saliva, evaporation and cooling occurs when wind hits saliva)
Evaporative heat loss - Sweating or panting is regulated by body temp (humans & dogs)
What is regional and temporal Heterothermy?
Regional:
- Temperature not constant throughout body
- Countercurrent heat exchangers in legs and flippers
(whales, reindeers, Antarctic skuas)
Temporal:
Temperature not constant through time
(hibernation, daily torpor, winterschlaf aka bears)
Large mammals such as bears do not undergo true…
hibernation but simply sleep over winter (winterschlaf).
Their body temp always stays above 30oc but they still achieve metabolic savings of up to 75%. Respiration drops to one breath every 45 seconds and heart rate to ~12 bpm
