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BIO 241 > topic 8 - thermoregulation > Flashcards

topic 8 - thermoregulation Flashcards

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1
Q

what is homeostasis

A

regulation of an internal environment in the face of change in the external environment

does not imply a constant internal environment

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2
Q

what is negative feedback

A

change in variable triggers a response that opposes the change

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3
Q

what are the negative feedback mechanisms

A

stimulus - external or internal change in a regulated factor (ex: temp change)

sensor - detects the change in the condition

integrator - compares condition to the set point and activates effector

effector - a physiological change that returns the factor to the set point

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4
Q

what are the negative feedback mechanisms involved in temp regulation

A

sensor - temp detection nerves in skin

integrator - hypothalamus (figures out what to do with info it receives regarding temp)

effector - muscle tissue vasculature, sweat glands

oscillation in temp throughout the day

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5
Q

what is positive feedback

A

change in variable triggers a response that amplifies the change

does not lead to homeostasis (pushes system away from homeostasis)

birth
melting permafrost releasing methane is a positive feedback driving global heating

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6
Q

what is thermoregulation

A

regulating internal body temp impacts energy budgets

ambient temp (Ta)
body temp (Tb)

Ta (outside temp) determines how much energy is spent regulating body temp

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7
Q

how is heat generated in endotherms

A

metabolism

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8
Q

how can heat be exchanged with the environment

A

convection - heat is transferred to and from an organism through air or liquid

conduction - direct contact heat transfer

evaporation - loss of heat when water changes from liquid to gas - change of state is also a loss of heat because energy is required to cause the change

electromagnetic/radiation - from sun hits dark colours and becomes heat

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9
Q

what is the rate of heat exchange

A

conductance

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10
Q

why do larger organisms have lower conductance

A

lower SA V ratio

more SA = more conductance
less SA = loses less heat

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11
Q

what is a homeotherm

A

maintains “constant” body temp independent of body temp

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12
Q

what is a heterotherm

A

body temp fluctuates with ambient temp (instantaneous or delayed)

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13
Q

what is an endotherm

A

uses metabolism to generate body heat

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14
Q

what is an ectotherm

A

acquires body heat from environment (regulate body temp through behaviour)

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15
Q

are there heterothermic endotherms

A

mole rats only (use huddling strategy and keep body temp low)

almost all homeotherms are endotherms

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16
Q

what is regional heterothermy

A

animals with different body temps in different parts of their body

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17
Q

what are the characteristics of homeothermic endotherms

A

behavioural - seek cool or warmth
physiological - sweating, panting, shivering

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18
Q

what are the characteristics of homeothermic ectotherms

A

seek or live exclusively in stable environments or microhabitats

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19
Q

what are the characteristics of heterothermic endotherms

A

change in body temp seasonally (torpor, hibernation, or daily)

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20
Q

what are the characteristics of heterothermic ectotherms

A

behavioural - move between sun and shade
physiological - adjust metabolic rates based on ambient temp

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21
Q

what are the metabolic consequences of endothermy

A

have a higher mass specific RMR than ectotherms
as mass increases, mass specific MR decreases

endotherms have a higher mass specific MR than ectotherms

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22
Q

why is temp important for metabolism

A

enzyme activity varies with temp
temp drives metabolism which in turn drives performance

metabolic rate and max speed have similar response curves to temp as enzymes do

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23
Q

what is the relationship between ambient temp and body temp in ectotherms

A

1:1 - slope of 1

24
Q

what is a homeothermic endotherms response to changes in ambient temp

A

animals have to expend energy outside the thermal neutral zone (TNZ) and the amount of energy needed is related to the difference in ambient temp from the TNZ

25
Q

what is the TNZ

A

temp of max performance in endotherms
no energy needed for regulation
temp range where metabolic rate is basal

26
Q

what happens when ambient temp drops below TNZ

A

metabolic rate increases from resting state to create warmth

27
Q

what happens when ambient temp goes above TNZ

A

metabolic rate increases to cool down

28
Q

what does the slope of the line of RMR v ambient temp represent

A

slope of the line = animals conductance

29
Q

what are strategies to regulate temp below TNZ

A

shivering
vasoconstriction (less blood to periphery)
piloerection (increasing depth of fur)
decreasing SA
decreasing exposure (huddling/burrowing)
thermogenesis

30
Q

what are strategies to regulate temp above TNZ

A

panting
vasodilation
sweating
increase SA
decreasing exposure (to sun)
active cooling

31
Q

what is the benefit of high and low conductance

A

low (lower slope) = heat retention (arctic)

high (higher slope) = heat loss (tropical)

32
Q

what is the heterothermic ectotherm response to temp changes

A

no TNZ for this group
temp approaches optimum for proteins and enzymes (zone of optimal activity)
suboptimal = less activity

33
Q

what is behavioural regulation of conductance

A

minimise energy expenditure due to temp
moving to optimise heat exchange with the environment to attain ideal body temp

  • changing exposure (seek or avoid)
  • grouping (being around others)
  • migration (move to change ambient temp)

dormancy (torpor, hibernation)

34
Q

what is torpor

A

short (6-8 hour) reduction in activity (~10C - not all the way to Ta) in body temp and a lower metabolic rate

35
Q

what is the purpose of torpor

A

reduces energy to stay warm (esp when food is scarce in winter, low food conditions, or drought)

36
Q

what is hibernation

A

awake for 1-2 days periodically to release toxic waste (urine) then go back to sleep until winter is over

rapid recovery in body temp = characteristic of hibernation

37
Q

what is the main difference between hibernation and torpor

A

body temp drops to neat ambient temp in hibernation

38
Q

why is small size good for hibernation

A

large SA V ratio = easy to brin body temp up and down

39
Q

do bears hibernate

A

no - winter sleep (more similar to torpor)
low SA V ratio helps them conserve heat

body temp remains significantly above ambient temp (small drop to reduce metabolic rate and conserve energy)

wake up after a short period and excrete waste

40
Q

what are reasons for migration

A

temp regulation
ambient temp condition
scarce food
competition
predator avoidance

41
Q

how is conductance physiologically regulated

A

acclimation (ecto)
blood flow
insulation
fur length and colour change
sweating and panting
cryoprotectants (ecto)
shivering thermogenesis
non shivering thermogenesis

everything else ^ endo

42
Q

what are the physiological responses to the temp increase

A

Message to hypothalamus
Vasodilation
Sweating
Panting

43
Q

what are the physiological responses to temp decrease

A

Message to hypothalamus
Brown adipose tissue is metabolised to generate heat quickly
Vasoconstriction
Shivering

44
Q

what is acclimation

A

altering optimal temp for performance

changes to physiological processes that respond (typically to seasonal) temp changes

takes a longer time (not instantaneous)

45
Q

example: how does membrane viscosity acclimate

A

cold = increased viscosity
- cold acclimation = change phospholipids to be less saturated to decrease viscosity back to set point

hot = decreased viscosity
- hot acclimation = change phospholipids to be more saturated to increase viscosity back to set point

46
Q

what happens with vasoconstriction

A

Decreases conductance with environment
Endotherms = when cold to retain heat
Ectotherms = when hot to retain heat

47
Q

what happens with vasodilation

A

Increases conductance with the environment
Endotherms = when hot to release heat
Ectotherms = when cold to increase heat gained from environment (hot rocks)

48
Q

what are internal and external insulation

A

Internal = fat/blubber
External = fur/feathers

Piloerection - the fluffing of fur/feathers to increase the thickness of insulation

49
Q

what are the characteristics of dark fur

A

Absorbs light, generates heat outside insulation - doesn’t reach body as much
Heat lost to environment more easily by convection

50
Q

what are the characteristics of light fur

A

Allows light to reach skin, generates heat inside insulation layer
Skin stays warmer as fur protects loss
Some mammals have hollow hairs which let radiation transmit down shaft
Best winter combo = black skin, white fur

51
Q

how does panting cause heat loss

A

increases ventilation rate which increases heat loss by evaporation and convection

52
Q

what are cryoprotectants

A

used by ectotherms

Molecules (glucose, glycerol) produced to lower freezing point
Antifreeze proteins allow ice to form in extracellular spaces, but not internally and prevent crystallisation (sharp edges)

53
Q

what is shivering thermogenesis

A

Muscles move rapidly to generate heat but no movement

54
Q

what is non shivering thermogenesis

A

Brown adipose tissue (fat) (brown because it has a lot of mito in it) is metabolised by the many mitochondria contained in this tissue

Mitochondria using uncoupling protein UCP1 to convert energy directly into heat rather than ATP
Proton gradient in mito is used by UCP1 and not ATP synthase (redirection)

55
Q

when is non shivering thermogenesis used

A

organsims recovering from torpor, hibernation, and winter sleep

also newborns

BIO 241 (22 decks)

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