Thermoregulation Flashcards
What is homeostasis?
homeo (similar) stasis (state)
It it a dynamic process that is regulated by how the organism can change its behaviour/metabolism to maintain its internal environment to an acceptable range
what are the parameters that organisms must control?
pH,
water (volume and pressure of cells and blood plasma, osmoregulation),
solutes,
temp,
O2/Co2,
heart rate,
input/output
What is a Negative feedback mechanism?
A change in a variable under homeostatic control, triggers a response that opposes the change
sensor:
detects environmental conditions
ex. temp: nerve endings in skin
Integrator:
analyzes signal from sensor, compares conditions to the set point and activated an appropriate effector
ex. brain, hypothalamus
Effector:
causes a physiological change that opposes the deviation from the set point
ex. skeletal muscle, sweat glands
stimulus:
something that causes something else to happen, develop, or become more active
Negative feedback mechanisms work to
reestablish homeostasis
Positive feedback mechanisms are
change in variable under homeostatic control triggers a response that amplifies the change
good for achieving an outcome once
Positive feedback mechanisms push a system
away from homeostasis (produces more and more)
Amplifies the change
not homeostatic
Thermoregulation is
regulating the internal body temperature
Temperature has a huge impact on
energy budgets
_________ has a huge impact on
energy budgets
Temperature
Ambient temperature (Ta)
Body temperature (Tb)
What’s the same and what’s different for ectotherms and endotherms?
for ectotherms the ta and Tb are the same
for endotherms the ta and Tb are different (bc endotherms create their own heat)
heat is generated by
metabolism
heat can be exchanged with the environment by
conduction, convection, evaporation, and radiation
Endotherms use the heat made by
metabolism for ______
thermoregulation
Ectotherms let the heat generated by metabolism ________
dissipate into the environment
Body heat can be regulated by
changing the rate of heat gain and loss
Rate of heat exchange is called
conductance
Large organisms have ______ due to _______
lower conductance (rate of heat exchange)
smaller SA:V ratios
Small organisms have ________ due to ______
higher conductance (rate of heat exchange)
larger SA:V ratios
homeotherm:
maintains a constant body temp (Tb) independent of ambient temperature (Ta),
can be human or earthworm.
very stable temperature
most endotherms are homotherms
Heterotherms:
(Tb) fluctuates with (Ta).
mostly ectotherms, but some can be endotherms
ex. Freshwater fish whose (Tb) changes with seasonal changes in the water temperature (Ta).
Endotherms:
uses metabolism to generate body heat (internal heat generation)
Ectotherm:
aquires body heat from the environment, do generate heat via metabolism (but don’t keep or use that heat)
external heat source
ex. Ice fish are homeotherms and ectotherms because they live in a stable environment (ice water)
By reducing your ____ you don’t have to eat as much to maintain a _____ (heterotherms that are endotherms)
internal temp
higher body temp
at low temps, enzymes are
inactive
at high temps, enzymes are
denatured
the optimum temp for enzyme activity is
just before enzymes are denatured
as an endotherms Ta increases, its Tb _____
stays relatively the same
as an ectotherms Ta increases, its Tb ______
Increases proportionally
tb=ta
Where does thermoregulation occur:
Above and below the TNZ (thermal neutral zone)
occurs in order to regulate body temp
In the graph of “Ambient Temperature (Ta) and Metabolic Rate (RMR) in a Homeothermic Endotherm” the steeper the line, the:
greater conductance
In the graph of “Ambient Temperature (Ta) and Metabolic Rate (RMR) in a Homeothermic Endotherm” when the line is straight, that is the:
thermal neutral zone
minimal metabolic regulation occurs
In the graph of “Ambient Temperature (Ta) and Metabolic Rate (RMR) in a Homeothermic Endotherm” below the thermal neutral zone is
hypothermy
Shivering, vasoconstriction, piloerection, decreasing surface area, decreasing exposure (huddling/burrowing)
In the graph of “Ambient Temperature (Ta) and Metabolic Rate (RMR) in a Homeothermic Endotherm” above the thermal neutral zone is
(Hyperthermy)
Panting, vasodilation, sweating, increasing surface area, decreasing exposure (to sun),
longer term solution to regulate body temp, that are not instantaneous are
Growing fur/adding fat, shedding, changing color
Low conductance is an adaptation for
heat retention (in the arctic bc its cold)
High conductance is an adaptation for
heat loss (in the tropical bc its hot)
in “Ambient Temperature (Ta) and Metabolic Rate (SMR) in a Heterothermic Ectotherm” graph, as Ta increase, what stages does the SMR go through?
hypothermia
lethargy
activity
hyperthermia
the thermal neutral zone for homeotherms is between the :
lower critical temp and higher critical temp
what is Behavioural regulation of conductance:
Moving to optimize heat exchange with the environment to attain an ideal body temp
what are the four groups of Behavioural regulation of conductance?
exposure
grouping
dormancy
migration
exposure is:
Movement into or out of the sun/wind
Surface area
ex. organism going in the shade
Grouping is:
huddling together to share radiation
ex. bats in a cave
Dormancy (daily torpor) is:
reduce spending energy to stay warm (short 6-8 hr reduction)
“nocturnal” torpor helps conserve energy, high metabolic rate is “turned down” nightly/seasonally to reduce NRG requirements in cold, drought, famish environments.
dormancy (Hibernation) is:
when TB regulated close to TA,
huge reduction in metabolic rate,
lasts 2 weeks before arousal,
requires huge heat generation for arousal, awake for 1-2 days then repeats.
Migration is:
the Complete avoidance of poor environmental conditions
Ex. Whales, birds, caribou, butterflies
Physiological regulation of conductance is:
Making physiological adjustments to optimize heat exchange with environment to attain ideal body temp
ways to physiologically regulate conductance:
Acclimation
Blood Flow
Insulation
Fur Length and Colour Change
Sweating/panting
Cryoprotectants
Shivering Thermogenesis
Non shivering thermogenesis
Membrane acclimation: is
accumulation of changes in every cell acclimates the organism to their environment
Blood flow is in two groups:
Vasoconstriction: decreases conductance with environment (Endotherms, when cold to retain heat, ectotherms, when hot to retain heat)
Vasolidation: increases conductance with environment (Endotherms, when hot to release heat, ectotherms, when cold to release heat gained from environment)
Insulation:
internal (fat, blubber): internal insulation layer that slows the rate of heat transfer
External (fur/feathers): external insulation layer to slow rate of heat transfer
Plioerection: the fluffing of fur/feathers to decrease rate of heat transfer by increasing thickness of insulation layer
Fur/feather thickness/length regulates conductance by
giving better insulation
animals increase amount/thickness of fur between summer and winter
Fur coloration (dark fur) helps by
absorbing light,
generates heat outside of insulation layer,
easily lost to environment
Fur coloration (white fur) helps by
White fur: let’s light reach skin, generates heat inside of insulation layer, keeps arctic animals warmer
Fur coloration (hollow hairs) helps by
Hollow hairs: allow radiation to transmit down hair shaft, so that baby seals and polar bears gain most solar heat
Sweating and panting regulate heat by:
evaporation causing heat loss
Cryoprotectants
Molecules (glucose, glycerol) produced to:
1. Lower freezing point
2. Allow ice to form in extracellular spaces, but not internally
metabolic rate is zero but they’re still alive (makes them colder)
Ice-nucleating agents are when
Antifreeze proteins prevent ice formation
Shivering thermogenesis is when
Simultaneous action of antagonistic muscles generating heat without causing movement (shivering to make heat)
Non-shivering thermogenesis:
special fat tissue (brown fat) that is loaded with special mitochondria
Instead of using PMF for ATP production, it’s used to generate “heat” (the protons go through UCP1)
Used to raise Tb (especially in newborns)
