Anatomy 1352. This is Unit 1, Chapter 15, The Undercrown System. If you only read one chapter in the entire book, this is the chapter to read. There's no particularly difficult portion of this chapter. The biggest thing is most people know nothing about it, and it's a large amount of material.
It's a long unit. So that said, let's get into it. So as we always do, some introduction to medical terminology.
Here we have the combining forms for a number of things we use in endocrine. Whenever you see adeno, you're talking about a gland. Adreno or adrenal, adrenal glands. You'll get a note, you'll start noting here some of the words are basically the same in the Latinized version versus English. Andro, male.
The androgens are the male sex hormones. Calcio, calcium. Hypercalcemia.
Crine means to secrete. So endocrine means to secrete endo inward or into the bloodstream. Astro is female.
Estrogens. Gonad refers to the sex glands, both ovaries and testes. Most people usually use it in terminology, refer to the testes, but be aware it means the same gland or equivalent glands for both genders.
Homeo, the same. Homeostasis. Main function of the endocrine system is to regulate body functions to maintain homeostasis.
Iodo, iodine. There's an easy one. We need that for one of our hormones. We'll come back to it when we need it.
Cal is potassium. Natro is sodium. These are based on their Latin names, calium and natrium, which is why their chemical symbols are K and NA, respectively. A couple of glands going on here, parathyroid, pineal, pituitary. Yep, yep.
Those are the Latin versions of their English names. So, and then... thymothymus and thyroid, thyrothyroido. Pretty straightforward.
Suffixes for words. Crying can also be a suffix, meaning to secrete again. We talk about dipsia or thirst occasionally, polydipsia, excessive thirst. Pressin is to press down.
Tropin is to stimulate. We're going to discuss a number of tropic hormones. These are hormones that stimulate other glands. All right, nervous system, endocrine system. What we already know from the end of 1351, nervous system's main function is analyze sensory input, respond to it through motor output, as well as conscious thinking and everything along those lines.
But the endocrine system also plays a major role in regulating the body. Now, the nervous system is going to use neurotransmitters. Endocrine system, though, is using hormones that end up being transported through the bloodstream, and that's quite important.
So let's go on from that then. So what exactly does endocrine mean? What is the endocrine system? Well, it's a bunch of glandular tissues separating hormones.
Where? Into the bloodstream. Now, technically, they go out of the cells, into the fluid, the interstitial fluid around the cells, and then into the bloodstream. But their ultimate goal is they're pretty quickly into the bloodstream. Now, endocrine glands differ from a number of glands we talked about during Anatomy 1. The exocrine glands.
Easy examples of exocrine glands would be sweat glands. Sweat glands. exocrine glands secrete into a duct or tube that will travel out onto a surface.
Outside surface, inside surface, doesn't really matter, but it's secreted into a duct onto a surface. Secretions from exocrine glands are not entering into the bloodstream. So that's just there for comparison's sake as we get on to it. So now... The hormones produced by your glands fall into two categories.
They're either lipid soluble or... water-soluble. And we're going to get on to those.
Oh, just as we mentioned before, endocrine gland secreting into the fluid around the cells, the interstitial fluid, and then entering into the bloodstream. But either way about it, there's no duct or tube, and it's not going out onto a surface. Now, with the bloodstream, hormones are getting transported throughout the body.
And you see that many hormones have very widespread effects. Many hormones target a lot of different tissues. Not all, many.
So, and then in order for that hormone to have an effect, it's got to get out of the bloodstream at the capillaries and bind to hormone receptors somewhere else. We'll hit all that bit as we go along. So first off, there are these two different types of hormones, lipid soluble, water soluble.
Water-soluble hormones are basically proteins or short peptides, things along those lines. Lipid-soluble hormones are primarily steroids. These are steroid hormones. No, they're not illegal steroids. They're the naturally produced steroids within the human body.
There are exceptions to that. Not all of them are steroids, but the most abundant ones, ones you most likely to have heard of are steroids. So let's start with the lipid soluble.
Most of them, steroid hormones. And there is one universal feature. All steroid hormones start out as cholesterol, period. There's no exception to that. That is just what it is.
Now you can say, well, what do all steroid hormones come from? Look it up on Google. if you don't phrase things correctly, you're going to get in some intermediate between cholesterol and whatever you're looking at.
Just know it now. Steroid hormones are all come from cholesterol. They're all derived from cholesterol.
Cholesterol is the starting point for all of their synthesis. Doesn't matter how you phrase it. And this is one of the biological needs for cholesterol.
Thyroid hormones, there's only two of them in this group, T3, T4. And they are from a heavily modified version of the amino acid tyrosine. And it has a number of iodines attached to it.
This is our biological need for iodine. You might be saying, well, amino acid tyrosine, isn't that like, you know, water soluble? Tyrosine is about the least soluble.
There's only one that's less soluble in water, amino acid. And the modifications to it. make it even less soluble in water.
So that's far more soluble in lipids. And then the final one is a gaseous hormone, nitric oxide. If it's in the bloodstream, it's a hormone.
If it's used by the nervous system, and it is in some places, it's a neurotransmitter. But it's a gas that readily dissolves into lipids. So now lipid soluble hormones being present.
lipid soluble, they're not that soluble in water. Well, what's the main component of blood? As you're sitting there going, well, plasma proteins, red cells, yada, yada, yada. There's more water in the bloodstream than everything else added together. Water is the most abundant molecule in the human body.
So lipid soluble hormones being transported in the bloodstream, more than half water. They need some way to help transport them. Lipid-soluble hormones rely on transport proteins within the blood.
These are sometimes specific proteins, sometimes generic proteins, like albumin, that the hormones bind to. Now, the hormones aren't bound exclusively to the transport proteins. They do come on and off the proteins. So each hormone spends a small amount of its time free in the blood.
And when it's free of the transport proteins, it can diffuse out of the capillaries and go to cells. Now, for lipid soluble hormones, when they encounter cells, they can go right through the plasma membrane because the plasma membrane is more than half lipid. So these hormones. directly enter into cells.
The targets or the receptors for lipid-soluble hormones are exclusively inside the cell, so they're going to bind there. Many lipid-soluble hormones function by binding to receptor proteins within the nucleus, and then turn on gene expression. So then you get DNA as read, messenger RNA produced, messenger RNA goes out to the cell, interacts with ribosomes, you get new proteins produced. Back to transcription translation, unit three of anatomy one.
So this is how lipid soluble hormones work. Now the water soluble hormones These are in two broad categories. You have your peptide and protein hormones, all made from amino acids, polymers of amino acids.
What's the difference between a peptide and a protein? Well, peptides are small, proteins are larger. Is there a defined cutoff between the two? No. So this is the majority, though, of the water-soluble hormones.
The other group are... derived from what we call the, or are called, carcinoids. These are the prostaglandins and the leukotrienes. Now, carcinoids actually start out as lipids, but during the modification, they're made to be much more water-soluble. So, these prostaglandins, leukotrienes, more soluble in water than they are in lipids.
Now, There are a multitude of functions for prostaglandins, leukotrienes. However, members of both groups are incredibly important in inflammation. These are mediators or the regulators of inflammation. So now water soluble proteins easily transported in the blood.
They're water soluble. So they get in and out of the capillaries quite easily. Now.
When they reach target tissue, they cannot get into the target cells. So remember, water-soluble lipid membrane. So water-soluble hormones only interact with membrane receptors. These are receptor proteins on the surface of the cell pointing out to the exterior. They point out to the interstitial fluid, fluid between cells.
Water-soluble hormones always bind to membrane receptors. But how do we get the signal inside the cell? Well, there's a couple more steps.
We'll get to in a minute. Now, because that hormone does bind at the membrane, and there have to be additional steps, the hormone is usually referred to as the first messenger. And since there's a first messenger, you know there's going to be a second.
So, first messenger hormone. binds to the cell receptor, the hormone receptor on the cell surface, and through a number of proteins on the inside of the cell, you end up with generating a second messenger. Now, there are only a couple of different second messengers. One of the most common ones is called CAMP or cyclic AMP.
So it's the AMP, adenosine monophosphate, is twisted around and made into a circle. It comes from ATP. Now, CAMP is a regulator of protein function.
It works with things called kinases, which I won't ask you about, but we're going to talk about it briefly anyways. Kinases, when turned on, put phosphates onto proteins and thereby activating that protein. So in the case of your water-soluble hormones, many times they are activating existing proteins, but turning them from an inactive to an active state. It's a different type of regulation than you see with some of the steroid proteins. Now you might say, well, there's only a couple second messengers.
How does the cell know what to turn on? Well, a lot of cells use cyclic AMP. but the kinases differ based on what kind of cell it is.
So different kinases for a liver cell versus a kidney cell. Therefore, the cyclic AMP produced in those cells is going to end up triggering different effects. So now just understand the basics of the second messenger. Cyclic AMP is going to then activate other things within the cell. The details about kinases and such, never going to ask you.
All right. So we're now going to then think about also what goes on with hormones. How are they working? What are their functions? Well, several of them are involved in regulating fluids within the body.
They regulate the amount of salt, total amount of fluid, other characteristics of those fluids. How do they do so? A lot of those are working at the kidney.
And kidney therefore modifies what's the blood constituents. And then due to circulation of the blood has an impact on all tissues. Few of these hormones are regulating your metabolism, increasing, decreasing metabolism, increasing, decreasing energy production. Those hormones potentially are acting at every single cell within the body.
Several hormones are involved in regulating growth and development. And some of those hormones are functioning throughout life, but depending where you are in life, having different effects. So then there are several of them that are stress mediators.
They regulate how your body responds to stress, how your body is functioning during emergency or stressful situations. And then finally, of course, there are a few hormones that are involved in regulating. controlling the reproductive process. So these are the generalized functions of most hormones. Now let's go back and look at the prostaglandins and leukotrienes very specifically.
Most people when they're studying this and trying to figure out where are prostaglandins, where are the leukotrienes, they're looking in the middle of the work. Go back to the very beginning. Prostaglandins and leukotrienes end up being the first hormones we discuss. They're before the hypothalamus pituitary link, which is usually where most people think to begin. Now, prostaglandins, leukotrienes, technically hormones, they can also be called paracrine or autocrines.
Now, in the case of paracrines, autocrines, here, these compounds are having an effect. at the location they're made. So local effect.
They actually don't have to get into the bloodstream and back out of the bloodstream to have an effect. They're having an effect right where they're made. Paracrines are made by cells and affect the cells around them. Autocrines, auto is self.
Autocrines are prostaglandins made by cells that then modify how the cell is behaving. As long as you can tell me a paracrine, autocrine. local control, we're good. Now, we said before prostaglandins made from lipids, specifically lipids in the membrane.
But if you can just tell me lipids, we're good. What are the functions of them? Well, they're involved in pain responses, platelet clumping or aggregation. Prostaglandins are triggering fever.
They're modulating inflammation. These are their main functions. Now.
granted there's a lot of them, but functionality here. They can also affect airway size, muscle contraction, smooth muscle contraction, secretion of acids by the stomach, and a multitude of other things. Look at the top floor four, get those fixed in your mind.
Prostaglandins, pain, platelet clumping, fever, inflammation. Know those specifically. Now, we do take several medications, over-the-counter ones, that are going to decrease the activity of prostaglandins, usually by decreasing production of prostaglandins. So if you think how aspirin or ibuprofen work, well, it's pain reducer, right? Right, they're blocking production of prostaglandins causing pain.
They reduce fever and inflammation, right? Yes, they're blocking the production of... prostaglandins that control fever and inflammation.
And why do old people take aspirin to prevent heart attacks? To prevent the first step in heart attacks, which is usually blood clotting. And the first step of blood clotting, platelets clumping together, platelets aggregating.
So now you might be saying, well, aspirin works better for me, but not ibuprofen or ibuprofen works better for me, but aspirin not so much. That's because pain, fever, inflammation controlled by several different prostaglandins, aspirin, ibuprofen. have differing effects on production of those prostaglandins. One is better against some, one is better against others.
That's what we have. So know your prostaglandins, know your leukotrienes from a general point of view. So now typically in here, we always have questions. These are also printed in your lecture outlines. Go ahead and use these to help you study.
These, of course, are not comprehensive. They're just hitting some of the highlights, some of the most important points. So if you want to discuss these, show up to the help sessions, the optional ones, and I'll happily go over every one of the question slides with you and anything else you wish to discuss.
So let's talk about controlling hormones now. So how do you do this? Well, an endocrine gland, when it is stimulated, it's going to release bursts of hormones.
Now, these hormones may be made and stored in the cell waiting for release, or when stimulated, the cell may at that point be producing the hormones, whichever one, not that important. But when these glands are stimulated, they release small bursts of hormones. And then the blood level of the hormones goes up. So what triggers these glands to release?
Could be direct nervous system control, which you see for the hypothalamus. You see it for part of the pituitary. And you also see that at the adrenal gland or portions of it. That's one way to trigger hormones, nervous system.
Second way, these glands are sensing changes within the blood. They sense a chemical change in the blood. They just then automatically produce the hormone. And some glands are stimulated by other hormones to have their effect. Now, when we talk about hormones, virtually all of them work by what we call negative feedback.
There are a very few that work on positive feedback. So negative feedback. How do these work? Well, something has changed.
The hormone is produced. It brings back whatever characteristic was changed, brings it back to normal. As that characteristic returns to normal, production or release of the hormone decreases.
So a change stimulated more hormone, a return to normal caused less hormone. That's a negative feedback. In positive feedback, a change stimulates more of the hormone, more of the hormone, emphasizes or enhances or increases that change. And we'll do the examples of them as we go through things. So here we have at negative feedback.
This is the long version of what we just said. You get, well, actually, this one's positive feedback. Negative feedback. Change happens, hormone produced, return to normal.
So let's look at negative feedback. An example, you ate a big meal, lots of carbs, your blood glucose is going up because glucose is getting absorbed from the intestines. Pancreas senses increase in glucose, releases more insulin.
Insulin lowers blood glucose because more importantly, why? Insulin allows cells to absorb or take up sugar, thereby reducing the amount of sugar in the blood. That's the actual function of insulin. So sugar levels in the blood go down. What's the pancreas do?
Makes less insulin. Negative feedback. Now here you see positive feedback.
And one of the best examples of positive feedback is the... birthing process. Some of you have went through it. Others, you have friends, relatives who have went through it.
You know what we're talking about, but let's look at it. So as birthing is beginning, uterine contractions pushing baby head against the cervix, causing a stretching of the cervix. There are stretch receptors there in the cervix, send a signal to the brain.
What's the effect of the brain? Brain produces or specifically the pituitary produces, oxytocin. Oxytocin is a hormone.
What's oxytocin do? Oxytocin stimulates the uterus to contract more, more frequent and more forceful. So what happens then? Well, more contracting, more pushing causes more stretching of the cervix, which causes more production of oxytocin, which causes more contractions, and it keeps amplifying.
So contractions start out weaker. and farther apart. And as birthing progresses, contractions become far more forceful and more frequent. The whole process continues until baby's out. And then the lack of pushing on the cervix, because, you know, baby's out, no more stimulus, no more oxytocin coming.
So a similar process is involved in nursing and lactation. as far as release of the milk from the glandular tissue, and that's stimulated by infant and regulated also by oxytocin. The only other example I can think of positive feedback has to do with blood clotting, and we're not dealing with that today. My favorite example for positive feedback, birthing and oxytocin.
Why? It's one everybody understands. It's very clear and straightforward. Good starting example. And it's the one we always use on quizzes and tests.
So now what glands are we talking about? Well, some glands in the endocrine system, their only function is producing hormones. Other glands, no, they have other functions beyond production of hormones.
So that's what we're going to go with here. Pituitary gland produces hormones only. Same with thyroid, parathyroid. the pineal gland, which you may not have ever heard of before, and the adrenal glands.
Now, there's other very important glands that have functions besides just making hormones. Hypothalamus, thymus, pancreas, ovaries, and testes fall in that category. Now, these aren't the only things that produce hormones. These are just what we generally refer to as the hormone-producing glands. You might be going, well, wait a minute.
Isn't the hypothalamus part of the brain? Yes, it is, but it does produce hormones. It actually produces hormones that start out as neurotransmitters. They just happen to go into the bloodstream and therefore function as hormones.
But it's not just these nine or 10, whether or not you include the hypothalamus, organs that produce hormones. There are other organs that their primary function is not hormone production, but they do produce them. Kidneys, stomach, liver, intestines, even the heart produces a hormone.
So we'll hit some of those at the appropriate times. Anything to do with digestive, though, we'll deal with that in the digestive system. Kidneys and kidney regulation, we will talk about some here today.
However, we'll do more of it when we do urinary system. So we're going to keep coming back to hormones. frequently throughout this semester. So where are these things all located?
Let's start down south. Testes located in the scrotum. Clearly not for aesthetics. It's there for temperature regulation.
In female anatomy, go a little bit higher into the pelvic cavity. And there you have the ovaries going upward. The pancreas located behind the stomach.
It's close to midline. It crosses midline a little bit more on the left than the right. And then the adrenal glands, adrenal. They're on top of the kidneys, hence the name adrenal. Their other name is suprarenal gland, which literally translates as above the kidneys.
So there's four of your glands. Move up into the chest region. You have the thymus. It sits directly above the heart in front of the trachea, right behind the sternum. We'll discuss it later on.
Going up farther up, you have in the neck the thyroid gland, little butterfly-shaped gland, wraps around part of the trachea. If you're sitting there feeling your neck going, I don't feel anything there, it's a very thin, light, delicate tissue. No, you can't feel it easily. And then there's the parathyroid.
Para means next to. Where's the parathyroid gland? Next to the thyroid.
Specifically, though, the parathyroid are four small spots on the back of the thyroid. They start out as a little bit different tissue, and they do produce a single hormone that is different from the thyroid hormones. So there we have already seven of our glands.
By the way, you should know their locations. Let's go up into the head where we find the last three. Now, you should remember from 1351 location of the hypothalamus, it's roughly center in the head at the base of the brain.
Hanging beneath the hypothalamus is the pituitary gland. We'll discuss a little bit more of that later. Now, there's a third one in the head called the pineal gland.
It's more towards the back of the brain. Is it at the complete back? No, but it's farther back than the hypothalamus and the pituitary.
It's a few inches back from there. The pineal gland is part of the epithalamus, so that should be something that rings a bell from 1351. So that is our locations though. Let's go back to this.
I do use some very common terminology that most people use in describing locations of these glands. Everything from the neck down, easy peasy. The head is where some people get tripped up. So where's the hypothalamus?
It's at the base of the brain about the center of the head. Where's the pituitary? Right below the hypothalamus.
So also about the center of the head. Where's the pineal gland? The key terms here are towards the back, not at the back, just back farther than hypothalamus and pituitary.
So pineal gland frequently described as towards the back of the brain. So common terminology. Now the hypothalamus and the pituitary are a pretty big chunk of this unit, so instead of taking a break in the middle of hypothalamus pituitary, let's take this time to end part one of unit one, and then we'll start part two at this location.