Endocrine lesson 1, Introduction and pituitary

good so you've heard of glands haven't you a gland is a structure or something which produces something so we looked at lymph nodes last week didn't we and we found out that the word really glands because they don't really produce anything but glands produce things that's the business they're in and there's two sorts there's endocrine and this EXO EXO crime glands they are the two types and the difference is that the exocrine glands have ducts so you have a gland for example it might be a sweat gland which is a coiled tube like this goes to the surface of the skin so sweat is produced in the bottom of the gland and it goes up this duct to get to where it wants to go so exocrine glands export products from the glands via a duct so you might think of saliva glands they produce saliva and then you have saliva Redux taking the saliva into the mouth so EXO crying lands export produced material from the gland via a duct they export it now in the old days the endocrine system used to be called the duct less gland system it's a bit of a mouthful ductless glands system so we don't call it that now we call it the endocrine system but it is a series of glands where there is no ducts the product is made in the gland but it's not exported via a duct and of course today it's the endocrine system we want to focus on endocrine so in an endocrine gland there's going to be cells with nuclei as you would expect so they would be endocrine cells and endocrine glands are well perfused with blood they have a abundant vasculature running through them so here we see one of the capillaries running through the endocrine gland and in the endocrine gland there are secrete Ori physicals that produce the product so whatever molecule it is this endocrine gland is producing is going to accumulate in these vesicles and then at the appropriate time these vesicles will merge with the surface membrane of the gland and that will release their contents and the capillary is very close by so the contents essentially go straight into the blood now some endocrine glands produce products that are used locally they just just diffuse locally the endocrine glands we're thinking about today the main endocrine system the endocrine product goes directly into the blood so an endocrine gland releases its product directly into the bloodstream and of course from there the blood can circulate to all parts of the body in the systemic circulation the product can end up going everywhere so that means imagine this product is like this you get this product in the blood and of course the product of an endocrine gland is a hormone so a hormone is the product of an endocrine gland systemically circulating in the blood now can you see that this particular hormone is is round as an MP so round one that represents a particular molecular shape so the different endocrine hormones produced by different glands have different molecular shapes and the whole point is that the endocrine gland can communicate with body tissues this is a communication system so in the body as you know messages can be transferred around the place quite quickly and coordination can be facilitated using your own or transmission in the nervous system this is an alternative way or an additional way that messages are transmitted around the body via endocrine hormones so these hormones are circulating around the body and then you come across the cell like this and on the surface of this cell there is a square receptor is this round endocrine hormones going to fit neatly neatly into that square receptor so it's just going to float on past isn't it not interested in that one and then as it goes around the body it might come across a cell with a triangular shaped receptor we're going to fit into that one and still know what is it but then it comes across a cell with a nice reciprocal shaped round receptor you see it can fit in there quite snugly can't it so it will fit in there and this round hole where the hormone fits into is called a receptor site and it's a protein it's a receptor protein but it's specific a specific receptor has been engineered by this cell so it can receive this particular hormone this particular endocrine product so in this context can you see that the hormone is the key and the receptor is the lock that the key fits into the lock and key idea or to put it another way the hormone is a signal as a signal molecule that fits into a particular receptor a receptor protein that makes this cell the target cell and this cell will be part of the target tissue that the endocrine hormone is aiming to influence so the ones it doesn't want to target or ignored because they don't have the right receptors but what it does want to target the signal molecule fits into the receptor molecule and that's good now I've drawn the receptor molecule on the outside of the cell here sometimes those receptor molecules inside the cell as well later on we might see there's some hormones called steroids there's another hormone called thyroid hormone in that case the receptor is inside the cell in that case the hormone would diffuse into the cell and bind to the intracellular receptor but it's the same it's still a signal molecule binding with a receptor molecule now once the signal molecule is bound into the receptor molecule that will bring about additional changes inside the cell that will bring about biochemical changes inside the cell and their specific networks of chemicals inside the cell waiting to spring into action when the signal molecule combines it with the receptor molecule to give that signal and the changes that go on inside the cell a mediated via what is called a secondary messenger system and that brings about some physiological change in the south will stimulate the cell to do something and because the release of the endocrine hormone is coordinated that means that the activity of the cells of the body can also be coordinated functioning in an ordered meaningful way something about this mysterious process of physiology so this context the hormone would be called the primary messenger system taking the message from the endocrine hormone to the cell and the change that is brought about inside this cell will be the secondary messenger system so we have two messenger systems coordinating physiological change inside the cell and of course this can affect millions billions of cells all at the same time bringing about coordinated activity that's basically our endocrine hormones work is that easy I'd want a minute to talk about it hmm that easy can't you go strong to the next bit which but yep so the endocrine hormones circulates in the blood it ignores the receptors it doesn't fit into when it does fit into the receptor that it fits into it is the combination between the hormone and the receptor that triggers off the or the changes inside the cell so the hormone on its own can't trigger changes inside the cell the receptor on its own can trigger changes inside the cell anymore than the key can open a door without a lock or a lot can be opened without a key you need both then when you've got both the cell knows it's time to spring into action and that combination of the hormone the receptor the signal and the receptor that triggers off some physiological change inside the cell yeah what kind of physiological changes well it depends very much on the type of cell and on the type of signal molecule so for example we were already noted if this was insulin and this was an insulin receptor the change will be the cell membrane becomes permeable to glucose molecules and that port will coordinate the regulation of blood sugar levels or if this is another type of hormone that will bind inside the cell called thyroid hormone the more thyroid hormone that binds into that receptor inside the cell the more metabolically active the cell would become and it will produce greater amounts of energy so different hormones are coordinating different ranges of physiological activity in different tissues but we'll see more when we learn about the individual endocrine glands good who knew that already is that easy done this somewhere before we can slide this done but don't talk about that would you want to go on a bit on a bit okay so the endocrine system needs to be controlled and coordinated and the main organ of control and coordination in the body of course is the brain isn't it 100,000 million individual neurons between 1,000 and 10,000 synaptic interconnections per cell it's complicated coordinating organ and there's a bit of the brain called the hypothalamus so here's the bottom part of the hypothalamus here this bit here is the high phone the hypothalamus is one of the bottom parts of the brain the bottom part that I both Alamos is like a Norse talk like this and that little stork widens into a dome like this and this lobe is part of what we call the pituitary gland and it's actually the back of the posterior gland so it's the posterior lobe the posterior lobe of the pituitary gland the pituitary gland is only the layman's term what do we call the pituitary gland if we're talking on the wards and we said pituitary gland there's a risk the hoi polloi would understand it isn't that kind of that we need our language in ordered of it the pituitary gland is the hypothesis the hypothesis so the pituitary gland is the hypothesis and this back part of the pituitary gland actually there's big nerve cells in here have big axons that run all the way down into the posterior lobe of the pituitary gland so really this is kind of like an extension of the brain really there's big axons project down interesting so the posterior lobe of the pituitary gland is made of Neurological type tissue it's almost like part of the drain so it's called the new Evoque called the new omo hypothesis because it's made of neurological tissue well it keeps me in a job and keep students on the toes now hasn't got three notes the whole bland we haven't finished the whole the whole gland is the hypothesis we'll see in another bit to it now this bit of the hypothesis at the back is made of neurological tissue so we call it the neuro hypothesis neuro just means neurological doesn't it and hypo fighters is the pituitary gland what you've written out a hundred times it won't seem so bad because in surgery there's a process called a hypo Feist ectomy ectomy removal of so occasionally it becomes necessary to remove the hypothesis to remove the pituitary gland in the process of high-profile sector me yeah that could be one of the reasons for it right now the fun part of the trophy's on there something different from the front part of the surgery gland is a larger lobe by this in front of course is anterior isn't it that is the anterior lobe of the pejorative lung and the anterior lobe of the pituitary gland is made of glandular tissue and the prefix that means glandular is a dino ad e mo are den OH so the anterior pituitary is made of completely different tissue if you look at a section of the pituitary gland there's a completely obvious histological border between the two lobes this is one type of tissue neurological tissue and this is a completely different type of tissue which is glandular tissue I just got what a adeno a DM needs to do with glandular tissue glandular so we've got the neuro hypothesis at the back and the adeno hypothesis at the front and this is glandular tissue so let's think now about what these structures produce and we'll just do a few examples of what they produce but with the neuro hypothesis the posterior pituitary it's quite easy only produces two things so the new hypothesis produces a hormone called oxytocin and another hormone called anti diuretic for low now the thing that oxytocin is famous for is stimulating the contraction of the myometrium the muscular part of the uterus during childbirth so oxytocin stimulates contraction of the uterus and after the baby's been born oxytocin also stimulates the smooth muscle in the milk ducts to facilitate lactation it stimulates the process of what is called milk letdown it stimulates the milk to go from the lobes of the breast where it's produced out of the nipple so the baby can suckle it there's other things as well but that's what it's famous for oxytocin also brings about a lot of emotional changes associated with childbirth and delivery and generates feelings such as attachment and love which of course are chemical reactions in the brain aging by the oxytocin effect now I think I bought this neuron out now because these these chemicals these hormones the oxytocin and the antidiuretic hormone are actually produced in the hypothalamus and let down into the gyro I Pro fighters from release so willed that one out now the hypothalamus actually produces all sorts of hormones so many hormones are produced in the hypothalamus these hormones are unusual in that they don't go into the systemic circulation they just take a short cut so blood comes into the hypo badness goes around kapila's in the hypothalamus where these hormones are absorbed into the bloodstream but instead of going to the systemic circulation they just take a little shortcut down to here so the dedicated system of blood vessels that takes them down to here and then once the blood is circulated through the anterior lobe of the pituitary gland through the adeno hypothesis that blood then drains into the systemic circulation quite a new doesn't it so it's a vein that begins in capillaries and ends in capillaries when that happens we're calling a portal system and there is only one other example in the body of a portal system which is the other portal vein in the body there's only one other one hmm no that's in the kidney foams capsules of the kidney the other one goes from the gut to the liver it's the hepatic portal vein that's the only other one and what's produced here a products that have different names in different textbooks but we can call them releasing hormones so releasing hormones in very small amounts go into the blood in the hypothalamus go down through this portal vein into the anterior lobe of the pituitary gland and it's only when these releasing hormones from the hypothalamus arrive in the pituitary gland that the pituitary gland releases its hormones and the hormones from the pituitary gland are released directly into the blood into the systemic circulation so the releasing hormones are produced in very small amounts in the hypothalamus and stimulate the release of releasing hormones from the anterior lobe of the hypothalamus from the adeno hypothesis that's good because it means these can be produced in very small amounts because you can see they're going straight to where they're needed that makes sense so they're not going to be diluted in all of the systemic circulation there just going to be ten kept in the relatively small volumes of blood going through this portal system to the anterior love and the hormones that the anterior lobe of the pituitary gland produces a collectively called trophic trophic hormones the hormones that are produced by the anterior pituitary gland under the influence of releasing hormones from the hypothalamus accord trophic hormones and it's these hormones that regulate the activity of the rest of the endocrine system so the endocrine activity or most of the endocrine activity in the body is coordinated via trophic hormones released by the adeno hypothesis to control the activity of the rest of the endocrine system now when I was a student in the old days people used to say that the pituitary gland is the master of the endocrine Orchestra it's kind of you know you can come in now and you come in now it's kind of conducting the whole the whole show but now can we see that the pituitary gland is actually only a puppet of the hypothalamus it only does what the hypothalamus tells it to do so the adeno hypothesis only releases its trophic hormones when it's stimulated to do so with the arrival of releasing hormones via the portal system from the hypothalamus so who's the real boss the hypothalamus is strictly in charge of the whole thing isn't it the hypothalamus that's in charge so the hypothalamus is the actual conductor of the endocrine wall castra it's the hypothalamus that's controlling him and not only does the hypothalamus produce the releasing hormones that control the release of the trophy or moves the hypothalamus also produces the posterior neuro - fie system of these hormones which is the oxytocin and the antidiuretic hormone amazing isn't it clever hypothalamus and he does dozens of other things as well I mean the reason you eat your lunch today is because the hypothalamus tells you to stimulate hunger it stimulates thirst it controls body temperature it stimulates sexual activity does all sorts of things causes all sorts of problems that I've both artists sometimes means you eat too much this stimulates eating what's um what's a diuretic know what you do when you get to the toilet yeah a diuretic increases your in volumes doesn't it diuresis means an abnormally large volume of urine so diuresis is a larger volume of urine than normal but this isn't a diuretic hormone is it it's not like giving cruise override an increase in your patients urine volumes it's an antidiuretic hormone so what does this hormone do to your own volumes it lowers your volumes so the kidneys can get away with it if the kidneys are just left to do their own thing they'll produce about 20 liters of urine per day that's what the kidneys like to do they passing about a liter of um per hour one here I mean it would be seriously inconvenient there is actually a disease where the hypothalamus doesn't make empty diuretic or would you know what it's called it's called diabetes insipidus insipid watery diabetes it's a type of polyuria diabetes insipidus but don't worry about like today so it's the antidiuretic hormone that stops the kidneys producing 20 liters of urine per day so the more water you want to conserve in the body the lower you want urine volumes to be can you see that means the more antidiuretic hormone has to be released from the posterior lobe of the pituitary gland from the neuro hypothesis so it's an antidiuretic hormone they will never just look at two or three examples of endocrine hormones released from the anterior well one is a growth hormone growth hormone creates the growth hormone so why do children grow well they grow because all the tissues that grow in the body pretty well all the tissues have grown the body are coordinated by growth hormone it is stimulating growth yeah that's a remarkably logical inference but no it's not it's probably not an easy question actually prostatic hypertrophy is caused by testosterone yeah if you castrate men they don't get prosthetic hypertrophy so it's caused by testosterone affecting the mature pituitary gland whether that increased testosterone is it is affected by growth hormones or anything else I don't using them the toddler the answer's no that probably the answer is that prostatic hypertrophy this caused by the way the maturing pituitary gland reacts to the testosterone it's probably not this this is a very logical thing to think the too much growth hormone you get a giant you get people that far too big which is remarkably unhealthy very tall people don't do very well or not enough of this of course and you get a dwarf that will cause dwarfism so thankfully you're all kind of about the right height so that meant when you were growing up your pituitary gland was really quite smart didn't release too much making you a giant didn't release not enough making you a dwarf release just the right amount which is good now this also controls the release of the well there's a hormone produced by the adeno hypothesis that controls the activity of the thyroid gland which we'll see in a minute so this one's thyroid stimulating for TSA so the activity of the thyroid gland in the neck is controlled by the amount of thyroid stimulating hormone released by the adeno hypothesis the amount of thyroid stimulating hormone released by the anterior lobe of the pituitary gland is controlled by the amount of thyroid stimulating hormone releasing hormone produced by the hypothalamus so that's an example of a trophic hormone thyroid stimulating hormone because that is causing the thyroid gland to release its endocrine product another example of a hormone produced by the anterior pituitary this is reno adrenocorticotropic hormone Adreno well that means to do with some glands will learn about later called the adrenal glands yeah the adrenaline is produced in the adrenal glands yes not in this part this is the adrenocortical and you might remember that the outside part of an organ is the cortex so this is the adrenocortical so we know it's affecting the adrenal gland we know it's affecting the cortex and trophic means to bring about a change or to stimulate so you can see this hormone it's a hormones chemical messenger which is stimulating the adrenal cortex it's adrenocorticotropic hormone ACTH good question how does alcohol inhibit or how does it affect antidiuretic hormone and the answer is the alcohol directly inhibits the release of antidiuretic hormone so the antidiuretic hormone is still produced but when there's alcohol around it's not released so if you drink alcohol that's going to inhibit the release of the antidiuretic hormone if you have less antidiuretic effect can you see that means you're going to have more diuretic you're going to have more diuresis no ecstasy affects something completely different it affects different chemical transmitter systems in the brain so if you have less antidiuretic hormone you have more diuresis that means you we lot of course that makes you dehydrated that's what alcohol does no ecstasy affects chemical transmitters in the brain called serotonin I think mostly 5-hydroxytryptamine the one that kind of caps you up and gets you going ah ah no no no I think when ecstasy's can cause it can cause hypothermia I don't think it stops you Ian I don't think it stops you drinking but it causes hyperthermia but if people are dehydrated when they have ecstasy then they're more prone to hyperthermia but this is kind of a malignant hyperthermia so sometimes when you give certain drugs it it seems to affect the hypothalamus turns the body temperature way up and with ecstasy you can turn the body temperature so I can kill you quite dangerous we call malignant hyperthermia learn about that when you do anesthetics as well there's a rare complication of anaesthesia right so can you see that this is oxytocin this is ADH and their trophic hormones they're bringing about changes in the endocrine system so what we need to do is explain the anatomy and physiology of the hypothalamus and this pituitary gland that's on a stalk in two lobes what's the neuro hypothesis why is it called that what is it - what's the Edina hypothesis why is it called that what does it do and how is its activity regulated by releasing hormones produced by the hypothalamus okay go for that

Channel: Dr. John Campbell

Views: 186,176

Rating: 4.9183674 out of 5

Keywords: endocrine, hormone, receptors, hypophysis, pituitary gland, anterior lobe, posterior lobe, human biology, live lesson, physiology, medicine, medical education, nursing, nurse education, bioscience

Id: pMn4nlYzTm8

Length: 43min 46sec (2626 seconds)

Published: Mon Apr 07 2014