animals can also use blood flow to help with thermo regulation. Vaso constriction or the constriction of blood vessels will help reduce heat loss, whereas vaso dilation actually increases heat loss. This is what I like to call the myth of the beer jacket. Often, people will say that by drinking alcohol they don't need to wear warm clothes out in the cold because the alcohol keeps them warm. Alcohol, though, actually results in vaso dilation, meaning those people have actually increased their heat loss in any apparent sense of warmth, is more or less in their heads. Now. Counter current exchange is going to be a really, really amazing tactic used to help, uh, maintain body heat. And we're going to see this idea come up again in other systems being used in other ways. So the concept is essentially having to flowing things that are next to each other and can exchange something with each other. Now what's really important is they need to be flowing in an anti parallel direction. So let's use the idea of veins and arteries to illustrate this point now arteries air going to be things that pump or that move blood away from the heart and veins move blood towards the heart. Meaning they're going to have flow in opposite directions, but they're gonna be located next to each other. So here we have an artery, and here we have vain, and our arterial blood is going to be carried again away from the heart. And that means to the extremities, right? Like our hands or our feet. So here in our IBIs or whatever, this is some bird. I'm gonna go with IBIs because I think they're cool birds in Are you concede E that as the blood is flowing to the extremity, uh, in the artery, it's coming back in the vein, these two blood vessels air near each other, and they're actually going to be able to exchange he with each other. And this is going to be a method of conserving body heat that's super effective. So essentially, what's going on is let's imagine that this is our artery. Me Hop out of the image here, and this is our vein. And as the artery carries warm blood to the extremities E in this case, the foot of the bird or something, that blood is gonna be really warm, the closer it is towards the core of the body. And as we get thio, the I don't know the edge, the extremities, whatever you wanna call it, it's going to get colder. Now here's the thing. That vein is carrying cold blood from the edges of the body towards the core right, so lets you know these air obviously make believe temperatures because, assuming this is in degrees Celsius, these fluctuations would have your blood freezing and also boiling. So you know these thes air kind of pretend temperatures for illustrative purposes now, as the cold blood and comes in from the vein, it's super cold zero degrees, whatever that is. Uh, the warmer blood from the artery here. It's not terribly warmer, 20 degrees or whatever you know, unit Um, so it's a little warmer enough so that it can exchange some heat with that vain so it's gonna move or it's going thio. Lose some heat to the blood in the vein that's headed towards the court as it is moving towards the edge. Now, as that blood in the vein moves even closer to the court, it's going to meet warmer blood in the artery that's also closer to the core. But again, on its way to the edge, this warmer blood, you can see there's still a difference. This side is going to be a higher temperature than that side, meaning that he is again going to pass from the blood in the artery to the blood in the vein, warming up the blood in the vein. And this continues on towards the core. This vein, the blood in the vein, gets warmer and warmer as it comes in contact with warmer and warmer blood from the artery because it's getting closer and closer to the court. This has the function of heating the blood in the vein up as it approaches the core, meaning you're not bringing some really cold blood from you know, the edge of your body into your core and making it super cold in there. Likewise, you're not gonna pump some really hot blood from your core all the way to the edge and kind of waste all that heat that it carried with it. This is a way of conserving the heat, and it's extremely eloquent if you think about it, because there's not really any energy being expended to do this. You're just simply constructing this system in such a way where the heat flows passively between the two things and ensures maximum conservation of that warmth. So this again is known as counter current exchange because we have two currents that air running anti parallel to each other and they're exchanging something. In this case, heat. We're going to see other examples were different things. They're being exchanged in equally eloquent and wonderful systems and strategies that animals have developed to survive. So that's all I have for this video. I'll see you guys next time.