Hello, everyone. In this lesson, we are going to be talking about how the different types of hormones actually get into the cell and do the jobs that they need to do. Okay. So let's go into our lesson, and we're going to be talking about the 2 major classes of hormones. They're going to be steroid hormones or lipid-soluble hormones, and they're going to be water-soluble hormones. So basically, there's a set of hormones that are hydrophobic and a set that are hydrophilic, and this is going to determine how they are going to get into the cell and how they are going to bind with their receptor. Okay, everyone? So we know that hormones are going to be long-distance signals that travel through the bloodstream. And they're going to be made by very specific glands, and they're going to be taken up by very specific cells. So we're talking about steroid hormones and water-soluble hormones, and steroid hormones and water-soluble hormones are different because of their composition, but they're also going to be different based on how they affect the cell. Steroid hormones generally have very long-term effects and it's going to be a very slow cellular response. It's going to take a long time for that cell to respond to a steroid hormone. Now, water-soluble hormones actually have very quick effects, but they don't last terribly long. So there are 2 different types of hormones that are going to have 2 different types of effects. So whenever you're talking about a steroid hormone, this is going to be one that's derived from lipids. It's going to be something that's hydrophobic. And if you guys were wondering, examples of steroid hormones are going to be the sex hormones, and the thyroid hormones. They are all made out of lipids. So, estrogen, testosterone, thyroxin. These are all going to be lipid-soluble hormones or steroid hormones. Now, water-soluble hormones are going to be a little bit different. You guys may recognize one of these, and that is Epinephrine. Epinephrine and other water-soluble hormones are going to be composed of hydrophilic components, like proteins, or amino acids, and things like that. Okay? Alright. So, let's have a look at our diagram here, because it's going to be depicting how these two different types of hormones are going to get into the cell. So this is a steroid hormone right here, meaning that it's lipid-soluble. It is hydrophobic. And then, we're going to have a water-soluble hormone right here. So it's hydrophilic. It is not lipid-soluble. It's water-soluble. So first off, let's start with our steroid hormone. We can see that it has this line where the steroid hormone just simply goes through the plasma membrane. And that's exactly what happens with steroid hormones. Because they're hydrophobic and they're lipid-soluble, they can easily travel through the hydrophobic plasma membrane. So they just go right through the plasma membrane. They don't need any membrane-bound protein receptor. They do bind to a receptor, but it's going to be in the cytoplasm, as you guys can see. Cytoplasm as you guys can see. Oh, sorry. As you guys can see right here, this is going to be its cytoplasmic receptor. And then, once the steroid hormone, maybe it's estrogen, maybe it's testosterone, binds with its receptor in the cytoplasm, it is then going to travel into the nucleus. And, this is really interesting, steroid hormones, their main job is to alter genetic expression of that particular cell. So the complex of the steroid hormone and its receptor are actually going to determine which genes are going to be transcribed, which ones are not. So which genes are going to be expressed in which cells, and that is going to create these newly created mRNAs, which will become these new proteins or new gene products. So, for example, a hormone that does this would be estradiol, which is a form of estrogen, and it is going to enter liver cells, and it's going to alter the genetic expression of liver cells. And this genetic expression is going to be making these products that the female will use to build eggs. So you guys can think about this, building eggs and forming eggs is a very long-term process. It takes a lot of energy and a lot of effort and takes a long time, and steroid hormones are going to trigger that beginning of that long process of the liver creating these different components of the egg cells. Specifically, the liver is going to be important for creating the yolk of the egg cell. But, I told you steroid hormones take a little while to have their effects, and that one does as well. So now, let's move over to this one right here. I'm going to go out of the picture, so you guys can actually see the rest of this image. Okay. So we have this particular hormone called ACTH. You guys can look it up if you want to. You don't particularly have to know that at this moment. You'll learn more about that, I believe, in osmoregulation and excretion, but you don't have to know that exactly at this moment. So, ACTH is very interesting because it is water-soluble. Water-soluble. So what does that tell us? That tells us that it is a hydrophilic molecule, meaning that it can't simply diffuse through the hydrophobic cellular membrane like our steroid hormone did. So it's going to have these receptors. You guys can see them here in the cell membrane, and ACTH has actually bound to one of them. This is going to trigger a response. This is going to trigger a transduction cascade, or a cascade of these secondary messengers. So, you guys see it's cyclic AMP is here. Cyclic AMP is a very common secondary messenger. So, basically what's going on here is the ACTH cannot get into the cell itself because it cannot get past the plasma membrane. So it's going to bind to the receptor, and then the receptor is going to send off all of these intracellular signals or secondary messenger signals. And those secondary messengers are then going to cause this cascade to happen. So as you guys can see, we have these cyclic AMP molecules here. They're going to be activating whatever these particular molecules are here, and then those molecules are going to activate these. And then, you guys can see that Cortisol, which is a different type of signal, was actually made. That is going to be the cellular response. So this process here of creating or activating all of these different messengers and these different proteins is going to be called a signal cascade or a transduction cascade. It's something happening where it's triggering all of these different signals, and then they are going to make the gene product, which is going to be cortisol. And this is actually a relatively short process, and it's not going to involve the changing of the genetic expression. So it's going to happen very quickly and it's not going to last a very long time. Cortisol is involved in stress, so it will only stay around as long as you are stressed. So it's a short-term period kind of thing. Okay, guys. So, now, we're going to scroll down and we're going to look at a little bit more stuff. We're going to look at how these different hormones can actually trigger different responses in the cell. Okay. Alright. So we're told that a hormone binds to the cell receptor, and then it's going to cause a particular cellular response. Well, it's interesting to know that depending on which cell that hormone is triggering, it's going to depend the type of response that cell is going to have. So the effect of a hormone depends on the presence of specific receptors. So unique receptors for the same hormone will cause different cellular responses. So for example, one hormone can have many receptors. So epinephrine, which is also called adrenaline, is going to have many different types of receptors. Epinephrine is going to be a water-soluble hormone, so you're going to have many different cell membrane receptors. And depending on which receptor the cell has, it's going to depend how it's going to react. So in some cells, it can increase blood flow to the muscles. So in particular, muscle cells it will increase the blood flow. In the digestive system, it will decrease the blood flow. In the liver, it will tell the liver to start breaking down glycogen so it can put glucose into the blood so your body has fuel. So epinephrine has many different jobs depending on which particular cellular receptor that cell has. So these are some examples of the ones for epinephrine. You have alpha 1, alpha 2, and beta receptors. These are very common receptors for epinephrine, and they're going to cause different things to happen. So you guys can see down here that the first alpha one is going to lead to a cellular response that is smooth muscle contraction. And whenever you're talking about epinephrine, smooth muscle contraction is generally going to be dealing with the blood vessels. Constricting the blood blood vessels, raising the blood pressure, and diverting blood to the areas of the body that need it, like your muscles and your brain. Okay? And you guys can see that it also does smooth muscle contraction here. It's going to inhibit certain other molecules from transmitting because of the stress response, and very interestingly, it will cause the heart muscles to contract because they're pumping harder, pumping the blood. Because epinephrine, if you guys don't know, epinephrine is used in your fight or flight response, which is going to be your emergency response. So if you're being chased by a bear, you're being attacked, or you forgot something and you're panicking, epinephrine is going to kick in and it's going to cause your muscles to actually get more blood so you can run away from the dangerous thing. It's going to cause your heart muscles to contract, so you pump all that blood to your muscles that need it. And it's going to cause the glycogenolysis, which is the breaking down of glycogen in your liver to fill your blood with glucose, so your muscles have energy to actually run or do whatever you need. So, everyone, in this lesson, it was very important to realize there are 2 different types of hormones, hydrophobic or steroid hormones and hydrophilic or water-soluble hormones, and they're going to have different receptors in different areas of the cell, and one hormone can have many different receptors, which will lead to many different outcomes or cellular responses. Okay, everyone. Let's go on to our next topic.