Hi. In this video, we're going to talk about thermoregulation, which is a type of homeostasis 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 temperature is again called thermoregulation, 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, some terminology to go over: endothermic and ectothermic organisms. Endothermic organisms will generate their body's main source of heat internally through their metabolism. Ectotherms, 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 trade-offs. For example, endotherms have to eat a ton of food in order to maintain that body heat. Right? They need a bunch of food to provide the energy to fuel those metabolic processes that produce the body heat. That also means that they're going to 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. Ectotherms, on the other hand, are going to not have to spend as much time looking for food, and not require as much energy in order to maintain their body heat, because again they're going to absorb it from external sources. However, they don't have as much 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, you know a lot colder, they get colder, and that cold can actually slow down certain chemical processes. This is just 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, endotherm and ectotherm are terms that deal with where an organism's, 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 homeotherms 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 homeotherm because, as you can see, it really can only survive in this narrow temperature range. Outside of that, it's going to die. Now, just to be super extra clear, this mammal is a homeotherm. It's also going to be an endotherm because it generates its body heat internally. Now, this lizard here is what we call a poikilotherm. And basically, it can have a 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, as you can see from the y-axis, it consumes a lot less energy than the mammal does. Right? That's what the y-axis, which is a measurement of energy, shows. Again, unlabeled axes are always a bad thing. This one's labeled; 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 poikilotherm is going to use a lot less energy, regardless of the temperature outside, than is this mammal because the mammal is a homeotherm, and it's an endotherm. So it has to burn energy to maintain a very narrow body temperature range. So heterotherms, the last one to go over, basically, you know, use some strategies that are both homeothermic and poikilothermic. It's sort of a little bit of both of them. You don't need to worry too much about the specifics.
Now, how do animals maintain body heat? There are a lot of adaptations and structures that we have in order to maintain nice body heat. Most obvious among these is what's going on here, our skin. Right? Our integumentary system, which is the organ system that surrounds the body, and it's made of not only skin, but hair and nails as well. For example, in a lot of animals, they're going to 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. I mean, we've got this nice stuff on our 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 are other types of insulation that you can add though to increase the amount of heat you keep in your body. These again are going to be things like hair, you know, or fur, which again we don't have a lot of, but a little bit, believe it or not. That's, you know, what a lot of our hair is for is to maintain temperature. You know, feathers are going to 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 there, a lot of fat means a lot of heat retention or preventing a lot of heat loss. This is also why whales are going to have lots of blubber to keep them warm in the cold ocean.
Now sometimes we can take a more active approach, and an example of that is brown adipose 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 white appearance of most adipose tissue, you know, from just being fat. Now, mitochondria obviously make ATP, and this ATP 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 are also behaviors that animals can show that help affect thermoregulation. Shivering, if you've ever been cold, is a byproduct, or I'm sorry, 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, you know, just one type of behavior. Behind me here is actually a very interesting response that we still have, goosebumps. Right? You get goosebumps 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 goosebumps. It's a response that causes your hairs to stick straight up, and this actually will help with heat retention. Not everything is about keeping warmer, of course. Evaporation is going to be a technique used to 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 which, you know, will cool us down. It's going to absorb energy from our body, evaporate off, and cool down our bodies.
So there are tons of ways that organisms can try to maintain their body heat to keep it at that comfortable range of temperatures. With that, let's flip the page.