Endocrine System

by Jason Amores Sumpter
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the endocrine system is made up of glands, and these glands secrete hormones into the bloodstream. We call them endocrine glands because they're also glands that will secrete substances into ducts that will be delivered to various other sites in the body. And these air called X a cream glands now in terms of the digestive system, uh, the liver, for example, has a duct that connects to the small intestine as well as this structure here, the gall bladder. And it's going to secrete bile into that duct, and the bile will eventually be delivered into the small intestine. So in that sense, the liver functions as an exa Quran gland in that way, and it's not mutually. The two types of glands are not mutually exclusive. For example, the pancreas here, this particular gland acts as both an endocrine and extra Quran gland. It's going to act as an extra Quran gland in digestion, secreting digestive hormones into small intestine. But it also is a super important endocrine gland and helps maintain blood sugar homeostasis. So what is a hormone? Technically, it's just a signaling molecule produced in a gland that gets secreted into the blood stream and in the bloodstream. It's going to be able to travel great distances and the body to communicate with cells very far away from the source that secreted it. Now the endocrine system has a hand in a ton of different functions in the body. It's gonna play a super important role in development, growth and reproduction. I mean, for example, think about puberty. That's when your hormones start going crazy, right? Well, that's gonna be a lot of endocrine signaling happening now. The endocrine system will also help you respond to the environment in certain ways. A great example of this is the fight or flight response, which will trigger, you know, a surge of hormones in your body from the undercurrent system that help mediate your essentially your defenses In a tense moment, we'll talk more about that later. Uh, in. In addition, the endocrine system is going to be very important for home of static mechanisms. For example, we mentioned the pancreas and its role in blood sugar homeostasis. But pretty soon we're going to talk about, for example, how the thyroid and parathyroid help with calcium homey a Stasis. Now they're actually three types of hormone structures that hormones kind of get grouped into. And you know, these, uh, these labels are can be a little flexible. Maybe I should say so. Uh, if you encounter a different labeling system for them, that's totally fine. So, for example, we have poly peptide hormones. Sometimes people separate this into, uh, you know, peptide hormones and protein hormones. Because of the very different sizes of the two molecules, I'm just gonna keep them all together to make it simple. So these they're gonna be generally larger hormones and polar because they're made of amino acids. And that's gonna actually mean that they can't cross the cell membrane, but they're going to be water soluble now. This is important because whether or not a hormone can cross the cell membrane as we're going to see shortly will affect how that hormone eyes going to bind to receptors and act on a cell. And additionally, the fact that it's water soluble means that it can diffuse into the bloodstream and move through the bloodstream unassisted. Now a mean hormones Ah, sometimes called amino acid derived hormones are gonna be synthesized from the amino acids tyrosine, and these tend to be fairly polar, you can see an example of an amine hormone right here. Here we have on a mean hormone and behind me, much larger. We have a poly peptide now in the middle here. What we have is a steroid hormone, and these, hopefully you'll recognize this structure of cholesterol in this hormone. These are lipid soluble hormones, meaning that they'll be able to cross that cell membrane unassisted. They'll just diffuse through. But it also means they won't be soluble in water, which is why they have to be transported by proteins in the blood. And here again, this is a steroid hormone now, in addition to these classifications on structure hormones or sometimes also classified based on whether they act directly on tissues or whether they stimulate some other gland to secrete hormones. And we call thes two classes direct hormones, those that act directly on tissues to produce some result, and tropic hormones that stimulate other glands to secrete hormones. Because, as you'll see in the endocrine system, it's quite common for one thing. To chemically signal another thing. To have that chemically signal another thing and basically develop these signaling cascades of different glands with different hormones. So with that, let's go ahead and turn the page