Topic 8 - Thermoregulation

Question 1

what is homestasis?

Answer 1

the regulation of internal environment in face of changes in the external environment

Question 2

what happens in a negative feedback system?

Answer 2

negative feedback systems occur when a change in a variable under homeostatic control occurs, and triggers a response that opposes the change. A sensor detects the environmental conditions and sends it to an integrator, the integrator asses the signal from the sensor and determines if it has caused a change away from the set point, if it does then it activates an effector, the effector causes a physiological change that opposes the deviation from the set point.

Question 3

what happens in a positive feedback system?

Answer 3

a change in a variable under homeostatic conditions that triggers a response to amplify change.

Question 4

what is thermoregulation?

Answer 4

the regulation of internal body temperature.

Question 5

what is Tb?

Answer 5

internal body temperature

Question 6

what is Ta?

Answer 6

ambient (external) body temp

Question 7

what is conductance?

Answer 7

rate of heat exchange between organism and the environment.

Question 8

what is the relationship between level of conductance and body mass?

Answer 8

As body mass increases, conductance decreases. Higher conductance means they lose heat faster, the organism needs a faster metabolism to regenerate it.

Question 9

what is a homeotherm?

Answer 9

homeotherms maintain constant body temp, independent of ambient temperature. eg.Humans

Question 10

what is a heterotherm?

Answer 10

heterotherms have a body temp that fluctuates, eg. freshwater fish changing body temp with seasonal temp changes.

Question 11

what is an endotherm?

Answer 11

endotherms use metabolism to generate body temp. All endotherms are homeotherms.

Question 12

what is an ectotherm?

Answer 12

ectotherms acquire body heat from the environment, they do generate heat from metabolism they just dont keep it. Most ectotherms are heterotherms.

Question 13

what has a higher metabolic rate, an ectotherm or an endotherm of the same mass?

Answer 13

endotherms will have higher metabolic rates as they have to use metabolism to generate body heat.

Question 14

what is the relationship between enzyme activity and temperature?

Answer 14

as temperature increases, enzymatic activity increases until it reaches an optimal peak. after the peak the enzyme denatures, and can no longer continue working.

Question 15

what is the relationship between metabolic rate and temperature?

Answer 15

as temperature increases, both RMR and AMR increase, because more energy is used at higher temps, AMR goes up because activity take more energy at higher temperatures,

Question 16

what will the graph of body temp (y) and ambient temp (x) look like for endotherms and ectotherms?

Answer 16

when measuring body temp to ambient temp, you will see a straight line for endotherms, as they maintain a constant body temperature, and for ectotherms you will see a straight diagonal line at 37 degrees from the horizontal.

Question 17

what is the thermoneutral zone?

Answer 17

the thermoneutral zone is the temperature in which everything in the organism is acting normal.

Question 18

what is hyperthermy?

Answer 18

hyperthermy is the temperature above the TNZ where the animal begins to overheat, can be decreased by panting, vasodilation, sweating, increasing SA, decreasing sun exposure.

Question 19

what is hypothermy?

Answer 19

hypothermy is the temperature below the TNZ where the animal begins to get too cold, can be decreased by shivering, vasoconstriction, piloerection, decreasing SA, hiding/burrowing (decreasing exposure).

Question 20

how does conductance change with environment?

Answer 20

arctic animals spend much lower energy to maintain body temps are lower air temps, change is more dramatic in the tropics as temp decreases, so conductance is much higher, so much more heat is lost.

Question 21

do heterothermic ectotherms have a thermoneutral zone?

Answer 21

no. since they dont maintain a constant body temp, they dont have a thermoneutral zone, they match ambient temp. They do have an optimal temp zone they prefer to function at.

Question 22

can enzymes still denature in heterothermic ectotherms?

Answer 22

yes, they still have a temp at which enzymes dentutre, it is just at a higher range than that of endotherms.

Question 23

what are the behavioural regulation of conductance method?

Answer 23

1. exposure
2. grouping
   3.dormancy
   4.migration

Question 24

what is exposure?

Answer 24

movement into or out of wind or sun to decrease or increase exposure.

Question 25

what is grouping?

Answer 25

huddling together to share radiation, decreasing surface area to decrease heat loss.

Question 26

what is dormancy- daily torpor?

Answer 26

a short 6-8 hour reduction in activity, which has a 10 degree drop in body temp to lower metabolic rate, reduces spending energy to stay warm, seen in small animals.

Question 27

what is dormancy- hibernation?

Answer 27

used to regulate body temp close to ambient temperature, resutling in a massive reduction in metabolic rate, lasts about 2 weeks before arousal, arousal takes a massive heat generation and lasts about 1-2 days before the cycle repeats.

Question 28

can large animals hibernate?

Answer 28

no. the organism must be brought back up to regular body temp very quickly so large animals like bears cannot hibernate due to small surface are:volume ratios.

Question 29

what is migration?

Answer 29

complete avoidance of poor environmental conditions.

Question 30

what is acclimation?

Answer 30

making physiological adjustments to optimize heat exchange with environment to obtain ideal body temp.

Question 31

what does acclimation affect more endotherms or ectotherms?

Answer 31

acclimation mostly affects ectotherms as they respond to their environment for body temp.

Question 32

what happens to membrane viscosity as temperature increases?

Answer 32

as temperature increases, membranes become more fluid getting more saturated with fatty acids, to decrease viscosity.

Question 33

what is vasoconstriction and when does it occur?

Answer 33

vasoconstriction is the contraction of blood vessels to decrease conductance with the environment.
endotherms with it when they’re cold to retain heat
ectotherms use it when they’re hot to retain heat

Question 34

what is vasodilation and when does it occur?

Answer 34

vasodilation is the expansion of blood vessels to increase conductance with the environment.
endotherms use it when hot to release heat
ectotherms use it when cold to increase heat gained from the environment.

Question 35

what is piloerection?

Answer 35

piloerection is the ‘fluffing” of feathers or fur by decreasing rate of heat transfer by increasing thickness of external insulation layer.

Question 36

what is internal insulation?

Answer 36

fat/blubber that slows rate of heat transfer.

Question 37

what is external insulation?

Answer 37

fur/feathers that slow rate of heat transfer.

Question 38

how does fur and colouration affect conductance?

Answer 38

dark fur absorbs light and generates heat outside insulation layers so heat is easily lost to environment. white fur allows heat from sun to reach skin and generate heat inside insulation layers. Black skin with white fur is best for keeping heat. hollow hairs allow radiation to travel down shaft.

Question 39

what does sweating and panting do?

Answer 39

heat loss due to evaporation.

Question 40

what are cryoprotectants?

Answer 40

glucose and glycerol produced to lower freezing point that allows ice to form between in extracellular spaces but not internally. as temperature decreases the liver produces mass amounts of glucose so the concentration of solute is so high that the animals don’t freeze. only happens in ectotherms.

Question 41

what are ice-nucleating agents?

Answer 41

antifreeze proteins that prevent ice formation, animals produce them when temperature decreases, so proteins bind to ice crystals and don’t allow them to grow or pierce the animal.

Question 42

what is shivering thermogenesis?

Answer 42

stimulates action of antagonistic muscles to generate heat without causing movement.

Question 43

what is non-shivering thermogenesis?

Answer 43

instead of using PMF or ATP production, used to generate heat, special fat tissue that is loaded with special mitochondria, used by organisms to raise Tb.

Question 44

when glucose levels are low, the pancreas releases glucagon, which causes glucose to be released from cells into the bloodstream. Glucagon is acting as the…
a. stimulus
b.sensor
c.integrator
d.effector

Answer 44

c. integrator