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Biology: The Endocrine System


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About this Lesson

  • Type: Video Tutorial
  • Length: 10:04
  • Media: Video/mp4
  • Use: Watch Online & Download
  • Access Period: Unrestricted
  • Download: MP4 (iPod compatible)
  • Size: 109 MB
  • Posted: 07/01/2009

This lesson is part of the following series:

Biology Course (390 lessons, $198.00)
Biology: Animal Systems and Homeostasis (63 lessons, $84.15)
Biology: The Endocrine System (3 lessons, $18.81)

Taught by Professor George Wolfe, this lesson was selected from a broader, comprehensive course, Biology. This course and others are available from Thinkwell, Inc. The full course can be found at The full course covers evolution, ecology, inorganic and organic chemistry, cell biology, respiration, molecular genetics, photosynthesis, biotechnology, cell reproduction, Mendelian genetics and mutation, population genetics and mutation, animal systems and homeostasis, evolution of life on earth, and plant systems and homeostasis.

George Wolfe brings 30+ years of teaching and curriculum writing experience to Thinkwell Biology. His teaching career started in Zaire, Africa where he taught Biology, Chemistry, Political Economics, and Physical Education in the Peace Corps. Since then, he's taught in the Western NY region, spending the last 20 years in the Rochester City School District where he is the Director of the Loudoun Academy of Science. Besides his teaching career, Mr. Wolfe has also been an Emmy-winning television host, fielding live questions for the PBS/WXXI production of Homework Hotline as well as writing and performing in "Football Physics" segments for the Buffalo Bills and the Discover Channel. His contributions to education have been extensive, serving on multiple advisory boards including the Cornell Institute of Physics Teachers, the Cornell Institute of Biology Teachers and the Harvard-Smithsonian Center for Astrophysics SportSmarts curriculum project. He has authored several publications including "The Nasonia Project", a lab series built around the genetics and behaviors of a parasitic wasp. He has received numerous awards throughout his teaching career including the NSTA Presidential Excellence Award, The National Association of Biology Teachers Outstanding Biology Teacher Award for New York State, The Shell Award for Outstanding Science Educator, and was recently inducted in the National Teaching Hall of Fame.

Supplementary Files

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  • Bio_4184_EndocrineChart.pdf Bio_4184_EndocrineChart.pdf

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Recent Reviews

Endocrine Chart
~ NurseWendy

I couldn't download the Endocrine chart. It wouldnt open for me. I have Windows 7 and it wouldn't work for me. I was really hoping I could bring this chart to class with me. It looks so helpful.

Endocrine Chart
~ NurseWendy

I couldn't download the Endocrine chart. It wouldnt open for me. I have Windows 7 and it wouldn't work for me. I was really hoping I could bring this chart to class with me. It looks so helpful.

If we're going to start out a discussion of the endocrine system organs, you probably want to know, what's the endocrine system? Well the endocrine system is a series of glands. And why are they called endocrine? Well, perhaps we should contrast that to a term like exocrine. An exocrine, like your salivary gland, pours stuff out of the gland and into a spot. So, for example, your salivary gland has a duct. And that duct goes down into your mouth. That's an exocrine gland. You're gall bladder, that's an exocrine gland. Your endocrine glands are ductless. Generally speaking, these will diffuse their chemical products into the blood, so we have direct effusion of their materials into the blood and the materials that they produce are called hormones. So these hormones are chemical messengers. Messengers that you know about that can go from one gland in your brain, all the way down into your reproductive organs. Or, from the top of your kidneys to seven or eight different organs in your body. That's what endocrine land is all about.
Let's take a look at the plumbing of the endocrine system and take a look at some of these glands. Now, if you think about it and let's get this really good-looking bald guy to go with it. The whole idea of endocrine glands - and by the way, you see this chart? We have a downloadable version of this; you really ought to have it. Because I have to tell you, we are not going to go through every single hormone in this chart, what it's made out of and what it does. We'll go through a few of the more important ones and some of the ones I think that really show typical hormone function, but it's no clearer than this. This is wonderful. It tells the gland, what the hormones are that are produced, and really what they are, whether they're peptides or proteins or glycoproteins. This thing is very good. So, let's talk about the organs of the endocrine system. And you know if you think about it, there has to be a link between the endocrine system and the nervous system. Think of epinephrine, the thing that used to be known as adrenaline. Well, what made you have adrenaline? What made you have adrenaline was fear. What made you fearful? Seeing scary things. Seeing is nervous. Epinephrine is endocrine. They is a link between the nervous system and the endocrine system and it's called the hypothalamus. The hypothalamus is part of your brain. And it's literally the control center. It is the thing that controls so many of the other organs. Right below and attached to the hypothalamus is a gland called the pituitary. I'm going to jump over that for now and jump over to it, because that has some of those hormones I said I really want to talk to you about. Pituitary is a big one. I can tell you this. There are two parts to the pituitary, the posterior and the anterior. We'll come back later, and that's going to be up here.
In your neck is a gland called the thyroid gland, and the thyroid gland produces some hormones that control your metabolism. And that would be located right here and there are some spots of tissue on the thyroid gland and these are called your parathyroids. And the parathyroid produces a hormone called parathyroid hormone or parathormone. That particular hormone regulates calcium balance in your body. Just below your stomach, you've heard of an organ before that was not endocrine. It was an exocrine gland because it poured out pancreatic juice. What was that organ called? The pancreas. What's it doing here? Because the pancreas has other functions, too. You see, the pancreas has islands of tissue that are endocrine in nature. They're called the islets of Langerhans. And these islets of Langerhans or the islands of Langerhans produce two hormones we're going to talk a little bit about, insulin and glucagon, that control your blood sugar. As we move on down, right at the top of the kidneys are the adrenal glands. And that's where the where adrenaline came from.
Epinephrine and norepinephrine are the hormones that we talk about there and epinephrine is the "fight or flight" hormone, like you see a lion walking down the street, so your heart starts beating hard. And it also produces mineral corticoids and glucocorticoids, things that control a lot of your salt balance, etc. The adrenal glands have two parts, too. The adrenal medulla and the adrenal cortex. And those are steroid hormones. So they're the ones that are going to diffuse directly through the cell membranes. Then we get down to the gonads and there aren't too many people like this guy because he has both testes an ovaries, but we have to put them in there. And the testes and ovaries are going to produce hormones that are going to give you your secondary sex characteristics, what goes with being a male or a female, and your primary sex characteristics, menstrual cycle, sperm development in the testes, that's all going to happen from the hormones produced right there. And then a couple that we're going to add at the end of the chart, the pineal gland and the thymus. The pineal gland is up near the top of your body, up in the brain area, and that produces a hormone that's getting a lot of publicity these days, melatonin. Body circadian rhythm kinds of things. Interesting. And the thymus gland.
So this is the tour of the endocrine system, but I want to talk about some of the control mechanisms because you know, getting back to the them of, if you understand how its done, the details fall into place. And I want to go back to the pituitary gland and talk about that. And I want to talk about, in particular, four hormones that are very important in the thyroid gland. Or four groups of hormones. And they are in the part of the pituitary that is called the anterior part. And there is a posterior part, too, that produces other hormones. But I want to star a couple of hormones here. I want to star follicle stimulating hormone. I want to star luteinizing hormone. I want to star thyroid stimulating hormone. And I want to star adrenocorticotrophic hormone. Why? Because all of these are what we call "tropic hormones." They control other organs. And so, for that reason, the pituitary has always been called the master grand of the body. Now, just between you and I, it's really the hypothalamus because the hypothalamus produces tropic hormones for the pituitary. So, he's really in charge. Let me, before I leave you, give you just one example of how a tropic hormone might work. And I'm going to show you a hormone called thyroid stimulating hormone, or TSH. TSH, as I showed you right here, is a glycoprotein. And let's see how it works. Let me start in the hypothalamus - remember the boss. The hypothalamus is going to make a hormone called TRH, thyroid releasing hormone, which is going to go to the anterior pituitary, and the anterior pituitary is going to produce TSH, thyroid stimulating hormone. Thyroid stimulating hormone is going to be one of these things that it's going to into the thyroid and guess what? It's going to use cAMP as a second messenger. You guys know all about that so now you get an idea of how a second messenger might work. So, TSH is going to go into the thyroid, and using cAMP, is going to produce two thyroid hormones, T1 and T4, metabolic hormones. So, there are a couple of things here. One thing I want to show you is how we have a hierarchy of command. You see? Thyroid stimulating hormone stimulates the thyroid. It's tropic. TRH is tropic for the pituitary. Very, very controlling. And here's one last thing. The idea of negative feedback, which is another thing I want you to remember about homeostasis, organs talk to each other. Watch this. T1 and T4, when their concentration gets high, will talk to the hypothalamus and tell it, cool out with the TRH. And if the TRH stops getting made, then the anterior pituitary will no longer make TSH and the thyroid will stop making T1 and T4. It's a negative feedback loop. And there's still one more. Even the TSH date of surgery was that. So, built into this system are two things. We have an idea of tropic hormones, hormones that control other hormones; and feedback, something that brings you back to the days when you were learning about enzymes and yet, it's true in hormones, too. So, as you start to learn about some of the aspects of the endocrine system, remember, communication is everything.
Animal Systems and Homeostasis
The Endocrine System
The Endocrine System Page [2 of 2]

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