lec 16 Flashcards
what are some issues associated with ice ? with respect to frozen seawater, what is the big adaptation?
ice is physically sharp and can pierce the cell membrane, and freezing seawater builds up osmolites outside the cell –> cell becomes hyposmotic and risks dehydration as water leaves the cell
some fish (ex. winter flounder) express antifreeze prot (AFP). ice needs to build up from something; AFPs prevent a first instance of ice from being formed in the first place, inhibiting spread (“apposing force to nucleating agent”)
AFPs are more expressed in the winter months, and the result is that plasma freezing point decreases
how does thermoregulation of fever work?
fever is regulated by the hypothalamus
the point bw when the hypothalamus activates fever and the body responds incl a bit of a lag
in the time it takes the body temp to rise, shivering and vasoconstriction of vascular beds are activated (set point > body temp = feel cold)
[in other words i should be at 40 degrees but im at 37 degrees so i feel cold]
after hypothalamus wants to cool off, theres also a bit of lag, where u sweat and vasodilate (set point < body temp = feel hot)
what is the equation for metabolism? at what point can we have 0 metabolic rate? is this realistic?
M = C(Tb - Ta) where C is [cold response constant?] and Tb and Ta are the temperatures of the body and ambient environ, resp
theoretically, M can be achieved when Ta = Tb; however, we know this is not realistic as BMR occurs to keep the body functioning
if we compare two animals with high and low cold response constants, what do we observe?
high cold response constant = low insulation, whereas low cold response constant = high insulation
what i think this is saying is the cold response constant refers to the degree to which the body response to environment temp
ie if u have a fur coat, u don’t need to amp up body temp since ur alr nice and cozy –> low response
what is brown adipose tissue?
super high in mitochondria, which express uncoupling prot I (UCP I)
uncoupling proteins uncouple the ATP synthase from the ETC, so that the hydrogen gradient is used for friction (heat) instead of ATP production
think of it like a neck warmer :)
cold air entering delicate tissues is bad. what are some adaptations that animals have made?
as air is breathed in, it is heated up; as air is breathed out, it is cooled down (or in other words, the heat is conserved)
long noses provide more space for heating to occur between the air entering the nostrils and the air reaching the lungs
how does counter current heat exchange work? to frame this better, what happens when we don’t have counter current heat exchange?
as blood circulates to the extremities, what normally happens is that heat is lost at the extremities and needs to be rewarmed as it reenters the body
what countercurrent heat exchange does is cool down blood that is going to the extremities (since it is going to be lost to the environment anyways) and uses that heat to warm up blood that is returning to the body
what is the rete mirable?
rete mirable is a series of capillaries that cools the blood going to the brain
we see this in deer. deer have naturally thick fur coats, so they are very warm. when they are being chased by predators, metabolism goes up and a lot of heat is released. this risks overheating the brain and decreases chances at survival. the rete mirable cools blood down using counter current heat exchange, in exchange heating up blood going down to the body
seasonal acclimation strategies such as mice (adapting metabolic rate to stay constant between seasons) and foxes (get big fur coats in winter, lowering metabolic rate) can be qualitative or quantitative. make an argument for one or the other
foxes are quantitative, since they are growing more abundant hair to be thicker. mice are qualitative, since they are adapting efficiency of metabolism to be constant across all seasons
compare the tropics to the arctic. what do metabolic rates look like?
in the tropics, metabolic rates are high to combat excessive heating. conversely, in the arctic, metabolic rates are lower, since most animals have a fur coat keeping them warm
what is the difference between hibernation, torpor, and general sleeping?
hibernation: lowering metabolic rate for an entire season
torpor: lowering metabolic rate for a period of time (think a couple of hours over night time)
difference between torpor and sleeping is that sleeping doesn’t change metabolic rate significantly - it may lower a bit, but not to the degree that torpor does
