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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

Study These Flashcards
A

1:1 - slope of 1

24
Q

what is a homeothermic endotherms response to changes in ambient temp

Study These Flashcards
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
what is the TNZ
temp of max performance in endotherms no energy needed for regulation temp range where metabolic rate is basal
26
what happens when ambient temp drops below TNZ
metabolic rate increases from resting state to create warmth
27
what happens when ambient temp goes above TNZ
metabolic rate increases to cool down
28
what does the slope of the line of RMR v ambient temp represent
slope of the line = animals conductance
29
what are strategies to regulate temp below TNZ
shivering vasoconstriction (less blood to periphery) piloerection (increasing depth of fur) decreasing SA decreasing exposure (huddling/burrowing) thermogenesis
30
what are strategies to regulate temp above TNZ
panting vasodilation sweating increase SA decreasing exposure (to sun) active cooling
31
what is the benefit of high and low conductance
low (lower slope) = heat retention (arctic) high (higher slope) = heat loss (tropical)
32
what is the heterothermic ectotherm response to temp changes
no TNZ for this group temp approaches optimum for proteins and enzymes (zone of optimal activity) suboptimal = less activity
33
what is behavioural regulation of conductance
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
what is torpor
short (6-8 hour) reduction in activity (~10C - not all the way to Ta) in body temp and a lower metabolic rate
35
what is the purpose of torpor
reduces energy to stay warm (esp when food is scarce in winter, low food conditions, or drought)
36
what is hibernation
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
what is the main difference between hibernation and torpor
body temp drops to neat ambient temp in hibernation
38
why is small size good for hibernation
large SA V ratio = easy to brin body temp up and down
39
do bears hibernate
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
what are reasons for migration
temp regulation ambient temp condition scarce food competition predator avoidance
41
how is conductance physiologically regulated
acclimation (ecto) blood flow insulation fur length and colour change sweating and panting cryoprotectants (ecto) shivering thermogenesis non shivering thermogenesis everything else ^ endo
42
what are the physiological responses to the temp increase
Message to hypothalamus Vasodilation Sweating Panting
43
what are the physiological responses to temp decrease
Message to hypothalamus Brown adipose tissue is metabolised to generate heat quickly Vasoconstriction Shivering
44
what is acclimation
altering optimal temp for performance changes to physiological processes that respond (typically to seasonal) temp changes takes a longer time (not instantaneous)
45
example: how does membrane viscosity acclimate
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
what happens with vasoconstriction
Decreases conductance with environment Endotherms = when cold to retain heat Ectotherms = when hot to retain heat
47
what happens with vasodilation
Increases conductance with the environment Endotherms = when hot to release heat Ectotherms = when cold to increase heat gained from environment (hot rocks)
48
what are internal and external insulation
Internal = fat/blubber External = fur/feathers Piloerection - the fluffing of fur/feathers to increase the thickness of insulation
49
what are the characteristics of dark fur
Absorbs light, generates heat outside insulation - doesn't reach body as much Heat lost to environment more easily by convection
50
what are the characteristics of light fur
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
how does panting cause heat loss
increases ventilation rate which increases heat loss by evaporation and convection
52
what are cryoprotectants
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
what is shivering thermogenesis
Muscles move rapidly to generate heat but no movement
54
what is non shivering thermogenesis
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
when is non shivering thermogenesis used
organsims recovering from torpor, hibernation, and winter sleep also newborns

BIO 241 (22 decks)

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