lecture 17-thermoregulation Flashcards
part 1
what is thermoregulation
process by whcih animals maintain an internal temp within normal range
by maintaining thermoregulation what is achieved
internal thermal homeostasis
what does thermoregulation depend on
orgnanisms ability to control the exchnage of heat w/ its environment
do organisms expend a lot of energy with thermoregulation
some do, some don’t
what type of temp system does life exist on
large (below 90C-hotter than 100C)
can most cells survive below OC
no
why can most cells not survive below OC
due to formation of damaging ice cyrstals (happens a lot during thawing)
what adaptation do some animals have that allows them to surivive in colder temps
have the antifreeze moleq (ie glucose at certain []) or other adaptations that allow them to surive in colder temos
can most cells surive above 45C, why?
no, due to denaturation of proteins
why can some bacteria and proteins live at higher temps
adaptation to membrane to prevent melting and jave enough covlaent and non covlaent bonds
what is the temp range most cellular functions are limited to
0-45C
endotherm
organisms body temp depends on heat prodution from metabolism
ectotherm
body temp depends on heat from its environment
heterotherm
body temp can be depedent on metabolism or its environment (animals that hibernate)
homeotherm
animal whose body temp is constant (necessarily due to endothermy)
poikilotherm
an animal whose body temo is variable and dependent on ambient temp
look at how animals are classified in terms of how they regulate body temp
ok
with poikilothermy, body temp (Tb) varies with what
environmental (ambient) temp (Ta)
why with the graph on the notes is there a netabolic rate drop
because dont need increase metabolic activity to warm ourselves in higher temps
homeotherms have ______ body temps
constant
homeothermic endotherms have _______ high temps over a wide range of _______ ______
constant; ambient temp
thermoneutral zone
can maintain normal body temp w/ot needing to use energy above and beyond normal basal metabolic rate
how much higher is metabolic rate of endotherm than similarly sized ecotherms at rest due to wat
5-10x higher due to maintaining its high body temp
humans live in what type of thermo environment
thermo-neutral micro environment
what is human Tb supported by
“waste” heat byproduct of metabolic processes
human thermal biology is more organized around what
around heat dissipation (elimination) rather than generation or conservation
stable thermal environment for enzymes always function how
the same
homeothermic endotherm can be active in
cold
cost of being endothermic homeotherm
expensive: energy taken in dedicated to thermoregulation in energy budget
homeothermic endotherms cant get too
small
poikilothermy benefits
-energy cheap
with poikilothermy more energy is put towards
growth + reproduction since less is going to maintenance (thermoregulation)
are there minimum size constrainst for poikilothermy
no
are poikilotherms active or inactive in cold
inactive in cold - harder to get food, enzymatic rxn rate chnages
do homeotherms or poikilotherms have more mitochondria
homeotherms
do homeotherms or poikilotherms have more extsnive inner membrane
homeotherms
-ETC functions and more ATP synthesis
do homeotherms or poikilotherms have leakier inner membranes
homeotherms
-(H+) so dont go through ATP synthase so give off more heat
homeotherms have _________ body temp
constant
poikilotherms have _________ body temp
variable
are poikilotherms and ecotherms the same
no
what with our body can bring up/down temp
-sweat when hot
-shiver when cold
-face gets red b/c of blood flow
what is body temp regulated by
determined by balance between internal heat production and heat exchange with environment
what are four mechanisms organaisms use to exchange heat with environment
-radiation
-evaporation
-conduction
-convection
heat always transfers energy from _____->____ temp
high->low
how is heat loss and gain balanced
-reduce heat exchange overall
-performheat exchnage in a particular direction (ie gain and not lose heat)
-insulation
-cooling by evaporating heat loss
-circulatory adaptations
-adjusting metabolic heat production
all help with wjay
balanceing heat loss and gain
insulation is in what type of organisms
mammals and birds
-skin, feathers, fur, blubber, reduce heat flow between animal and its environments
why is insulation most important in marine animals
because conduction is faster in water than air (water heats up faster)
how do many animals lose heat
through evaporation of water from skin (even some ecotherms)
sweating or bathing moistens skin and helps with
animal cool down
panting increases what
cooling effect to in birds and many mammals
regulation of blood flow near body surface significantly affects what
thermoregulation
what can many endotherms and ecotherms do with blood flow
can alter amount of blood flow between body core and the skin
vasodliation
blood flow in skin increases, faiclitaing heat loss (increase diamter in blood vessels) -> lose heat by convection
vasoconstriction
blood flow in skin decreases, lowering heat loss
countercurrent exchnage helps with
redcing heat loss for animals in cold temps
in what types of organisms does countercrruent exchnage occur in
marine aniamsl and birds
countercurrent exchnage is due to
arrangemnet of blood vessels usually in externalities/limbs
countercurrent heat exchange trasnfers heat between what? how?
fluids flowing in opposite directions
-traps heat in core of the body
-reduce heat loss
in what type of fish does countercurrent exchange occur
-in some large, powerful swimmers (ie great white sharks)
-keeps major swimming muscles warm
-reduce heat loss
countercurrent exchanges in insects
bublebees and some moths have countercurrent heat exchnagers that help maintain a high temo un the thorax (important for flight in winter)
-to help maintain homeostasis in the hive (not individual)
thermogensis
the process of heat production in organisms
mechanisms that initate thermogensis
-increased by muscle activity such as moving or shivering
-low amplitude muscle contractions
-common in mammals
-birds some nonavian reptiles and some insects can also rasie body temp through shiverring
what organisms conduct non shivering homeogenesis
infnats of many mammals
-in adult mammals that hibernate
non shivering thermogeneis mammals have what
a tissue called brown fat that is specialized for rapid heat production
what type of fats do human adults have besides infnats
brown adipose tissue (BAT)
do fat or skinny people have more brown fat
skinny people have more brown fat b/c they have less insulation
what does BAT vary with
amount of BAT in human adults has been dound to vary depending on temp of urrounding environment
beige fat has characteristics of what
white and brown fat
-cells are embedded in WAT and can cause browning of the tissue (produces heat)
BAT is heavily
vascularized
BAT has lots of
mitochondria
what protein is expressed in BAT
uncoupling protein 1
what does amount of brown fat vary with
varies depending on temp of surrouding environment
norepenephrine stimulates what in BAT
stimulates large increase in metabolicly produced heat
where does BAT express UCP1
in inner membrane of mitochondria
what does uncoupling e- flow from ATP production allow (two things)
-lipid oxidation at rates for above normal levels for aerobic resp
2) immeditaley release of heat from oxidation of lipids rather than storage fo that energy in ATP
