hi. In this video, we're going to talk about thermo regulation, which is the type of home Stasis that controls body temperature. Now some organisms can function over a wide range of temperatures. Others are confined to a fairly narrow range of temperatures in which they can survive the regulation of body temperatures again called thermo regulation. And the sensors for this are going to be found in that important brain structure, the hypothalamus, which is the structure that bridges the connection between the nervous system and the endocrine system. The two major signaling systems of the animal body. Now Cem terminology to go over Endo thermic and ecto thermic organisms, endo thermic organisms will generate their bodies main source of heat internally through their metabolism. Acto therms, on the other hand, have to absorb most of their body heat from some external source. But this doesn't mean that they're incapable of generating body heat. It should be noted now. Each of these strategies has tradeoffs. For example, Endo therms have to eat a ton of food in order to maintain that body heat right. They need ah bunch of food to provide the energy to fuel those metabolic processes that produce the body heat. That also means that they're gonna have to spend a lot of time looking for food. Now. The advantage they have for this is they have a much more tightly controlled internal environment, which gives them certain advantages in terms of, you know, regulating various chemical processes. For example, Acto therms, on the other hand, are, you know, going thio not have to spend a much time looking for food and not require as much energy in order to maintain their body heat because again they're gonna absorb it from external sources. However, they don't have a site of control over their internal environment. So, for example, this can have an impact on their ability to carry out certain chemical reactions. If it gets a lot colder, they get colder and that cold can actually slow down certain chemical processes. This is just, you know, an illustration of some of the trade offs. There's obviously a lot more to it, but hopefully you can see that you know, no strategy is perfect. They all have their advantages and drawbacks. Now end of term and ecto therm our terms that deal with where and organisms Uh you know, main source of body heat comes from now let's talk about some terms that deal with how an organism deals with temperature variation. So homey Oh, therms are organisms that have to maintain a pretty constant body temperature, regardless of what's going on in the environment. A good example of this is going to be a mammal. So this mammal is a home eo therm because, as you can see, it really can Onley survive in this narrow temperature range. Outside of that, it's going to die now just to be super extra clear. Uh, this, uh, mammal is a home. Both, ERM it's also going to be a nen, doth, ERM because it generates its body heat internally. Now this lizard here is what we call a tequila therm. And basically it can have body temperature that varies quite a lot based on environmental conditions. As you can see, it functions over a much broader range of temperatures and also Aziz, you can see from the Y axis. It consumes a lot less energy than the mouse does. Right, That's this Y axis. Jewell is a measurement of energy again, unlabeled axes, always a bad thing. This one's labeled doesn't have any, you know, it doesn't have any markings on it, But you get the general idea here. It's just supposed to be illustrative. So you know, the idea is that this poor Akila therm eyes going thio use a lot less energy regardless of the temperature outside than is this mouse because the mouse is a homo therm and it's an end of term. So it has to burn energy to maintain a very narrow, uh, body temperature range. Um so hetero therms last one to go over basically, uh, you know, use some strategies that are both homo thermic and poykio thermic. It's sort of a little bit of both of them. Ah, you don't need to worry too much about the specifics there. Now, how do animals, uh, maintain body heat? There's a lot of adaptations and structures that we have in order to maintain nice body heat. Ah, Most obvious amongst these is what's going on here are skin, right? Are Integra men Therese system, which is the organ system that surrounds the body. And it's made of not only skin, but hair and nails is Well, uh, for example, in, um, you know a lot of animals. They're gonna be covered in a lot more hair than we are. And that hair will keep them warm. Ours doesn't do a lot for us. Got this nice stuff on her head. But, you know, obviously could have more hair and stay warmer. But just the skin itself helps keep in body heat acts as a barrier. There's other types of insulation that you can add, though thio, increase the amount of heat you keep in your body. Uh, these again, they're gonna be things like hair or fur, which again we don't have a lot of, but you have a little bit. Believe it or not, that's you know what? Ah, lot of our hair is forced to maintain temperature. Uh, you know, feathers there gonna be a nice example of another type of insulation that you know will keep birds warm. There are different types of feathers. Some are specialized in insulation like down, for example. The stuff we fill our pillows with fat also can reduce heat loss to the environment. And as you can see with this plump Arctic seal, their ah lot of fat means a lot of heat retention or preventing a lot of heat loss. This is also why whales we'll have lots of blubber to keep them warm in the cold ocean. Now, sometimes we could take a more active approach, and a new example of that is brown at a post tissue. This is a special type of adipose tissue that contains high concentrations of mitochondria, which are what give it its brown appearance, as opposed to the ah white appearance of most adipose tissue from just being fat. Now, mitochondria, um, obviously make a teepee, and this 80 p is what's going to be used for heat generation. So this is a more active approach in the sense of actually consuming energy to heat the body. There's also behaviors that animals can show that help affect thermo regulation. Shivering, if you've ever been cold, is a byproduct. I'm sorry, uh, is a way to produce heat as a byproduct of muscle movement. It's an involuntary response that moves your muscles to generate a little heat to try to warm your body. That is just one type of behavior behind me. Here is actually very interesting response, that we still have goose bumps, right? You get goose bumps when you get cold. This doesn't do a lot for us because we're not covered in fur. But if you've ever, for example, seen like a cat get puffy or something when they're cold, that's what's happening. They're basically just getting goose bumps. It's a response that causes your hairs to stick straight up, and this actually will help with heat retention. Um, not everything is about keeping warmer. Of course, evaporation is going to be a technique used. Thio uh, cool off, for example. Sweating right. We secrete sweat, which has water onto the surface of our skin. And when that water evaporates, it absorbs a lot of energy. When which, you know will cool us down. It's gonna absorb energy from our body, evaporate off and cool down our bodies. So there's tons of ways that organisms can try. Thio maintain their body heat thio. Keep it at that comfortable range of temperatures. With that, let's flip the page
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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.