Thermoregulation

Question 1

Heat production =

&

Heat transfer =

Answer 1

A. Thermogenesis

B. Thermoconductance

Question 2

Behavioural mechanisms

Answer 2

• Heat production - exercise
• Heat transfer - basking, retreating, posture

Question 3

Physiological mechanisms

Answer 3

-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)

Question 4

Potential environmental factors which might affect thermal regulation of an animal in an environment like the below

Question 5

Types of Animal Thermoregulation

Poikilotherm:

Homeotherms

• Ectotherms:
• Endotherms:

Answer 5

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

Question 6

Familiarise

Question 7

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)

Question 8

Leatherback turtles can maintain bod temp ____ ______ than sea surrounding them.

Answer 8

Leatherback turtles can maintain bod temp 18oC higher than sea surrounding them

Question 9

Homeothermic/Poikilothermic endotherms =

Answer 9

A Mesotherm

Question 10

Galapagos marine iguanas are a

poikilothermic/homeothermic ectotherm

expalin how?

Answer 10

• 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

Question 12

Familiarise

1. On land = tachycardia + peripheral vasocardia = to warm body
2. Diving = bradycardia + peripheral vaso constriction = retains heat around core/vital organs

Question 13

Whales and Dolphins

-homeothermic endotherms

Answer 13

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

Question 14

Naked mole rat

-mammal (cold blooded)

truly poikilothermic (no ability to regulate body temp)

Answer 14

body temp vs amient temp

Question 15

Main thermoregulatory organ…

Answer 15

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.

-

Question 16

When are thermoregulatory responses stimulated?

Answer 16

When the body temp is outside the thermoneutral zone.

TNZ for a naked human male is 25-30

(thermo neutral zone)

Question 17

What is Shivering thermogenesis?

Answer 17

A thermoregulatory response which activates heat in the muscles.

Question 18

What is Non-shivering thermogenesis?

Answer 18

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.

Question 19

What is behavioural thermoregulation?

Answer 19

-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

Question 20

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)

Question 21

What is regional and temporal Heterothermy?

Answer 21

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)

Question 22

Large mammals such as bears do not undergo true…

Answer 22

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