well hello there welcome back this is chapter 17 the endocrine system so this will be kind of the last time we'll think about command and control systems in the body we've been working on the nervous system for so long that it seems like that'd be the whole course but now we're going to transition away from that but one more step here when talking about the nervous system is its connection to the endocrine system and what I wanted to be able to do here during this lecture is have you understand that tight integration between the nervous system and the endocrine system this diagram here it's labeled figure 18 - 1 please keep in mind some of these diagrams many of these diagrams are for different textbooks in the salad and text that we use right now in this course the endocrine system is chapter 17 but this is showing there's a kind of an overview of the physical structures in the endocrine system and these are glands or glandular structures and one of the things we learned Oh back in chapter 4 or 5 when we learned about tissues and the integumentary issues during development form glands and when they secrete their glandular secretions to the outside of the body we call those exocrine glands when they secrete them into the bloodstream we call them endocrine glands and we call those secretions hormones so these are some of the major hormone producing structures and tissues in the body you'll learn the physical layout in lab this diagram here gives us an idea we talked about the endocrine system it's it's a form of communication in the body and remember the nervous system is also so the nervous system is a way for you know the brain and all practical aspects communicates to the body tissues through you know efferent action potential traffic and it also receives information through afferent sensory traffic so the you know the nervous system is a communication system also is Antron system but it exists in a larger context of cell to cell chemical signaling so this diagram here gives us an idea of how we view different modes of chemical signaling between cells so the first one here direct communication if you think about this we have two cells here that are directly adhered to each other and we've been through this before for example again talking about tissue dynamics with epithelial tissues stratified epithelial tissues especially they have a commonality of having a lot of gap junctions so if you think about two cells that are directly adhere to each other with a gap Junction they are sharing cytoplasm right and so if you took a look at the distribution effects here usually limited to adjacent cells of the same type that are interconnected great so this is a direct communication next we have paracrine communication here and if you look at paracrine in communication what do you got you got a cell here and it is directly communicating with not a physically adhered cell but at least neighboring cells so paracrine communication is really just a tissue level communication through the extracellular fluid the chemical mediators here what are called paracrine factors and we'll we'll look at some examples of that in this chapter and primarily limited to a local area or paracrine factors concentrations are relatively high target cells must have appropriate receptors so these target cells here have to have receptors for these factors but this is within a single tissue alright within a tissue then we have endocrine communication and a-crying endocrine this is through the bloodstream that's we're going to talk about in this chapter the chemical mediators here are hormones and the target cells here are primarily located in other tissues and organs so the hormones must travel through the bloodstream to somewhere else in the body to have their target tissue effects look we've put on here something we already know at a very basic level now synaptic communication this is chemical communication between cells what do you think's going on or the synapse right this is chemical communication between cells so there's cross synapse the chemical mediators are neurotransmitters but the impacts are limited to a very specific area in that very specific area is the postsynaptic membrane across the synaptic cleft we have a another category here that's on your lecture handout that's not on this diagram and I want to put it in here put it in here Auto crying I screwed that up a lot I mean erase that my little eraser going here my pen back Auto crying factors or Auto crying communication and when we take a look at what's going on here I want to I want you think about here's a cell right this cell releases autocrine factors into the extracellular fluid and these factors come back and impact the same cell that's where autocrine comes in were cellular secretions impact the cell that secreted them alright hi this is something that if we were to be talking about say the immune system with some t-cells and things like that we would come across I just wanted to get it out there we're not really gonna talk about this during this chapter but it kind of goes in with this whole set here I direct paracrine endocrine synaptic and autocrine these are all different forms of intercellular communication alright alright so this slide here is meant to give us an idea of some basic basic difference differences between the nervous system as a communication system versus the endocrine system as a communication system so what I want to do here is start by drawing a line okay so what do we have we have down on the bottom this is going to be our nervous system so if we take a look at the nervous system the nervous system is a frequency frequency modulated systems may highlight that see I have a highlighter isn't it cool all right so we have a frequency modulated system now what does that mean think about how a nervous system communicates it communicates with action potentials and on this graph here you know we have x-axis y-axis we were used to reading action potentials in terms of time on the x-axis and millivolts on the y-axis right at negative 85 for example you know insert whatever your resting membrane potential is and these lines here represent an action potential spike now keep in mind we've everything we've learned about action potentials is one action potential is the same as the next is the same as the next is the same as the next you can't generate a stronger exponential they just are what they are and they're all the same so we have to think about how does the nervous system encode into its signal the strength of the signal now how does a pain receptor tell your brain that that's a little bit painful versus a lot painful right so what do we have to do here if all action potentials are the same the only way we can modulate this system is by changing the frequency of the action potentials so if you think about a weak signal here on the left alright down here let's say that your nosey scepter is sending a pain signal to the to the brain that together it's just a little bit painful if you were listening in on the action potential traffic it might you know sound something like click click click click click click ok a certain frequency of how fast those nociceptors action potentials are reaching the brain let's say you crank up the pain a little bit and it's a little bit more painful what you would hear is click-click click-click click-click click-click click-click click-click so how fast the signals are coming in tells the brain how much pain and you get down here and click click click click click that's like oh my gosh somebody's tearing my finger off so when we look at how the nervous system communicates strength of signal it can't change how strong or weak and exponential is they're all the same all they can do is change the frequency up top here we have the endocrine system and the endocrine system this is well you know an endocrine gland releases molecules hormones into the bloodstream and then those molecules go through the bloodstream and impact target tissues the endocrine system is a amplitude modulated system so we have amplitude modulation this is kind of the opposite of the central nervous system or the nervous system in general because the nervous system is hamstrings so speak by the idea that you can't make a stronger action potential so you have to do everything by frequency it's not the case in the endocrine system what we do here if you're encoding oh we oh I gotta change that from my highlighter to my pen okay so in the endocrine system if we have a weak signal right what the endocrine gland does is it releases a little bit of hormone all right so look on the y-axis on this graph here hormone concentration in the blood so you release some of the hormone molecules into the blood and then if you get into a situation where you want to have a stronger signal right then you do more harm and then if you want an even stronger signal you release more or hormone so it's about how much hormone do you want to dump into the bloodstream for a weak signal you dump a little bit of hormone into the blood strong signal stronger signal we call this amplitude modulation all right so I'll put this on here strong signal equals release more more hormone this is amplitude modulation so the nervous system and the endocrine system operate differently alright so we'll use a whiteboard here one of the things we'll want to do also if you look on your lecture online I have the second kind of major category and electron line as endocrine versus nervous systems and we've talked about now the modulation now is that previous slide there frequency versus amplitude modulation we can also take a look at some other aspects of the major critical differences between the endocrine and nervous system when it comes to communication so I'm going to draw a little grid here like this and I'm gonna write nervous here right endocrine system here and I want to kind of compare like four different categories here alright and these categories I'll put along the side here we have speed we have duration that's duration we have modulation and we have impacts so I'll draw it like this yeah it's colorful right getting used to this just got to give me time so if we take a look at the nervous system compared to the endocrine system of speed we spent some quality time talking about the speeds of the nervous system I hit the speeds of action potentials and even when you're talking about having to cross a snapped ik cleft now the speed of that is measurable but it's negligible in the grand scheme of things so if we talk about the nervous system with speed here this is really fast and you know really fast if we take a look at the endocrine system think about what a gland does it has to manufacture hormones store them in storage vesicles and when the signal comes it has to exocytosed these hormones in the bloodstream the hormones have to circulate through general circulation you have to go back to the heart and they gotta go through the chambers of the heart and out of the lungs and back to the heart and out to the body and hope that as they go out of the left ventricle through the aortic arch and down to wherever they end up when whatever capillary bed they go through that they actually encounter a target tissue that has a receptor for that hormone so what that means is that an individual hormone molecule that's dumped into the bloodstream could have to go through the circulatory you know circuit several times before it actually comes across the target tissue that has receptors for it so there's you know if we we talk about the nervous system release versus the endocrine system this is really slow it could take minutes before that hormone starts to take effect in any real way any measurable way so there's there's a big difference there right so you think well why wouldn't you just do everything the nervous system why mess around with an endocrine system that's really slow well the next one here is important duration hey so if we take a look at the duration of an impact from a nervous system innervation you know a neuron synapses with the target tissue action potential comes down a neuron hits the synapse you release neurotransmitter and on that very little small piece of membrane that postsynaptic membrane you have a very you know specific impact on that one spot and once the action potential spike comes through it release a little bit of neurotransmitter and remember there's usually some way that the neurotransmitter is cleaned out of the cleft in a very short period of time so when we look at the impacts from a neuron on a target cell the impacts are really short a short duration impact on that target tissue whereas with endocrine hormonal shall we say impacts on tissues once those hormones bind to the cells they tend to stay bound and they tend to have impacts that last for a long time all right so this is a long duration so the endocrine system is really handy if you want to cause tissues to respond for a long time or over a long duration nervous systems are hard not good for that because if you want to take a tissue that has direct innervation and you want to keep that tissue say excited for example for a really long time know the neuron can and wear out it can fatigue you can overwork it so that it can actually cause problems if you try to use innervation to keep a tissue excited for a long time you're much better off using a hormonal pathway for that so they both have their their ups and downs they both have their they're both have drawbacks they both have benefits right if we look down here we've already talked to a modulation right the nervous system is frequency modulated whereas the endocrine system is amplitude modulated that's the previous slide and then the impacts if we talk about nervous system again a single neuron innervating a target tissue you have a very local impact a very local or very specific impact on a single cell whereas endocrine here we usually have regional or tissue or even organ system-wide impacts so you can release these hormones into the bloodstream and impact a wide range of tissues car cells all at once now this table here this is from the salad and textbook table 17 1 and they give you a comparison of the nervous and endocrine systems and has a lot of what we just talked about someone to give you that so you could have in a more formal way okay so what do we have here we're gonna take a look at the major structural categories of hormones where two hormones come from and what are some some commonalities amongst them you're going to see here this first category amino acid derivatives so there's a two groups here and these hormones are going to be single amino acids that have been modified chemically to turn them into hormones first ones are derivatives they say of tyrosine so tyrosine is an amino acid and derivatives of tryptophan which is another amino acid and they show the Thanksgiving turkey there okay so we take a look at derivatives of tyrosine derivatives or tryptophan so these are single amino acids that are again chemically modified you're gonna see another name given to these you're gonna see these called biogenic ends so if I can write sideways here biogenic amines so because they're dry from you know acids and so you might have come across that vocabulary so look we've got thyroxine here T 4 they call it so thyroxine a thyroid hormone that's the hormone that basically regulates your basal metabolic rate we have catecholamines or catecholamines they've got epinephrine here norepinephrine falls underneath this so your hormones involved with sympathetic activation and neurotransmitters of adrenergic neurons these are catecholamines and then derivatives of tryptophan we have melatonin here so this is one structural category hormones single amino acids either tyrosine and tryptophan that have been chemically modified then we get into the peptide hormones so peptide if you remember your basic cellular biology so these are chains of amino acids so if you look under this category here where they talk about peptide hormones they say our chains of amino acids and they there are two groups here glycoproteins and short polypeptides and small proteins so we take a look at the glycoproteins here what that means glycol means sugar proteins so these are protein chains amino acid chains that have carbohydrate side chains so they're glycoproteins and if you look in here we've got thyroid stimulating hormone luteinizing hormone follicle-stimulating hormone so there's a there's a number of these now we have the short polypeptides and small proteins so it says it's a diverse group of hormones and everything from short chain polypeptides now when we say short chain polypeptides for example ADH and oxytocin which they're calling out here at the beginning of that those are nine amino acids long that's a short chain polypeptide and then up into small proteins you know 15 one amino acids for insulin growth hormone 191 amino acids prolactin 196 amino acids so we we have you know a variety of protein types in here and chain links so we have the peptide hormones these are hormones that are basically protein chains various types lipoproteins short other peptides then we have the lipid derivatives so these are protein or these are hormones derived from some forms of nonpolar lipids do classes right we've got eicosanoids and steroid hormones so if we look at the eicosanoids here these are derived from a particular fatty acid 20 carbon fatty acid called arachidonic acid these kosa noids many of them are I'll write this in many of these are paracrine factors so remember we identified those as short distance cellular signals that act within a tissue to have a couple of different classes leukotrienes but what most people may be familiar with if you have any background in this is prostaglandins these are a primary paracrine factor and there's a large group of prostaglandins out there with the steroid hormones down here so they're showing estrogen and this diagram steroid hormones all have the same basic structure because they are all derived from cholesterol so cholesterol which we many of us probably first learned about cholesterol in terms of the plasma membrane and you learned about cells so the four components that plasma membrane phospholipid bilayer cholesterol proteins and the glycocalyx cholesterol here is fantastically common in cells because it's a core component of membrane every steroid hormone is produced from cholesterol so there's our major classes of hormones amino acid derivatives single amino acids peptide hormones which are basically derived from proteins and lipid derivatives and what you're going to find here if you think about this as we move forward if we take the amino acid derivatives and the peptides these are going to be polar molecules if we take a look at the lipid derivatives these are nonpolar this come important when we think about how they impact cells how the hormone actually finds its target tissue and acts upon it polar hormones are going to have to either bind to surface receptors or have some sort of transporter that moves them across the membrane because they're polar and they can't go across by themselves the lipid derivatives being nonpolar will be able to pass directly across the plasma membrane and enter the cell without any help so here I've put up part of our electron line just because I know sometimes it's helpful for us to write stuff in so we keep them mined here one of the things we wanted to keep track of when we take a look at these classes or hormones I've just taken those three classes and they're on the list here we have amino acid derivatives peptide hormones the lipid derivatives if we take a look at you know acid derivatives these are small polar if you look at the peptide hormones these are large polar look at the lipid derivatives these are nonpolar if we come up here and just kind of fill this in just gonna keep track of this stuff the amino acid derivatives of biogenic gamma means we've got t4 the thyroid hormone here we've also got the catecholamines catecholamines sometimes you'll hear people call it that would be epinephrine and norepinephrine we have the tryptophan which is the melatonin here so just some common examples of hormones of each group down in a peptide hormones we have from the black go proteins we have some common ones that you will learn in lab remember you can learn all of these in lab I got TSH which is thyroid stimulating hormone we have FSH follicle stimulating hormone we have LH which is luteinizing hormone in the small chain polypeptide small protein category a couple of big ones here ADH and oxytocin there's many more but just give you a few to keep track of we take a look at the lipid derivatives here there are eicosanoids number prostaglandins here those are those are a big one and remember these are paracrine factors then steroid hormones remember these are all derived from cholesterol and you know some some examples sake testosterone estrogen I recognize a few of these etc all right here your textbook gives a few you know examples structural examples of some of these groups we've got change the color here so we've got the steroid hormones here so there's test strong there's estradiol we've got the monoamines here so the biogenic a means the single amino acid derivatives there's a catecholamine epinephrine and there's t4 thyroxine right over here we have in the peptide examples you know the protein examples there's oxytocin here so that's all ADH and oxytocin they're very similar here's insulin so that's each one of these yellow balls and these examples represents a single amino acid so these are short chain polypeptides and so you can tell that insulin here is a quaternary protein with two polypeptide chains linked together here's an interesting look at some of our steroid hormones so remember cholesterol here is the foundation for every one of these so this shows metabolic pathways for example you take cholesterol and turn it into progesterone so this is just a modified cholesterol molecule and from progesterone then you can manufacture testosterone and then from testosterone you can manufacture estradiol which is very close to estrogen or from progesterone you can manufacture cortisol hydrocortisone that is your stress hormone or we can use progesterone to produce aldosterone and this is a hormone that we will get familiar with when we look at kidney function so all of these if you look at this entire diagram they're all just various flavors of cholesterol here we're back to a part of your lecture outline and I wanted to put this up because here we want to talk about the distribution may actually write on this here let's talk about the distribution here of hormones and what we mean by this is when an endocrine cell releases that hormone into the bloodstream Wow what happens to it how does it travel in the blood let's get a couple options one is freely circulating here so you could have this hormone molecule freely circulating just dissolved in the plasma now keep in mind this is pretty rare all right so I wanna track something here first of all freely circulating this is a low proportion of your circulating hormones this is fairly rare because what happens is if it's freely circulating it's here's a few things that could happen let's say you're freely circulating what's an option what are the options for I have is a hormone option number one you actually find your target tissue bind to it and do your job okay great that's what you want to do but as you're freely circulating through the body other things are happening at the same time if you're just in general circulation in the plasma more often than not you get peed out you find your way out through the kidneys and out through the urethra because there's nothing keeping you from being filtered in the glomeruli of the kidneys now we're gonna learn about the kidneys later this semester but yeah if you're just kind of freely floating in the plasma there's a pretty good chance sooner or later you're gonna get it speed out and then three here which you have to understand is you have a number of defense mechanisms in your body and one of those is to remove things from your blood that could potentially be harmful and in order to do this some of these mechanism are nonspecific their indiscriminate so one option is you could be broken down in the liver or four you could be broken down by circulating enzymes so what do we think about this one of the measures of hormone effectiveness and you know hormone dynamics we have is called a half-life the circulating half-life so it means after what's the time period after which 50 percent of the hormone has been removed from the bloodstream that was put in so call this the circulating half-life when we look at freely circulating hormones we have about a 30 minute half life freely circulating hormones don't last very long in circulation if we look at all the rest remember I said this it's a low proportion it's fairly rare most proteins circulate bound to plasma proteins and these plasma proteins are either albumins or globulin as we call them albumins and globulin these are very large plasma proteins and they actually have receptor sites on them that carry molecules like hormones around in the bloodstream so when we look at this a half-life in these cases can be measured in days or weeks so if they're bound on these plasma proteins they can hang out for a very long time and that's how most hormones circulate this diagram here shows our three basic patterns of hormone secretion if you take a look up at the top here right we have what's called chronic hormone secretion so what they're trying to show you you know I could stretch this x-axis way out and they're showing it over time there's minor fluctuations but over time this hormone stays relatively stable in the bloodstream so they give you the example of thyroid hormone all right and remember just because it is stable doesn't mean it can't change levels so over time you could change levels and they could stabilize and then over time it could change levels and stabilize again but chronic secretion means that that gland is for all practical purposes at any given time secreting now hormone at the same rate all the time and down here we have what's called acute hormone secretion this is where the hormone is only released in response to a particular stimulus so if you look here they've tried poorly to draw arrows of different size so if you have a pretty good stimulus bump that creates a strong release of hormone a lot of hormone gets left out or let the blood if you have a tiny little stimulus bump you get a little bit of hormone and then you get in the middle and you in the middle alright so with the acute hormone secretion the level that the hormone is released at is is equivalent to the strength of the stimulus that is supplied they use the example of insulin here so if you have a big meal this first arrow here's your big meal then you get a lot of insulin released if you have a little snack in between meals you get a little bit of insulin you get the idea if we look at the last one episodic here this is you might just think this is a different version of the top one but it's not so it particular predetermined points you get a certain secretion it Peaks comes back down to baseline and then again up and down and then again up and down so they give the example down here the reproductive hormones regulating stration so luteinizing hormone for example you get a peak of luteinizing hormone once a month and that regulates ovulation and we're gonna talk about that on the reproductive chapters so chronic secretion acute secretion episodic secretion three general patterns by which hormones are put into the bloodstream this diagram here is going to help me talk to you about secretion control this is at the bottom of the front page of your chapter outline so underneath there if you look you see secretion control humoral neural and hormonal so I'm going to put some of this up here just as notes so if we talk about secretion control all right so we have humoral so what we're we're trying to get at here is what actually causes the endocrine cell to release its hormone into the bloodstream when we talk about humoral control this is a response to local conditions response to local conditions and oft and these are these fall under the category of paracrine factors not always but often for example when we get into the digestive system soon that'll be our next major chapter we're going to talk about intro endocrine cells individual endocrine cell types that line the digestive tract so for example in the stomach we have parietal cells and chief cells they also have G cells that produce gastrin gastrin is a hormone and these cells don't release gastrin unless food enters the stomach and once food enters the stomach then they release gastrin into the bloodstream so that is a classic example of humoral control the local conditions determine whether or not that hormone is released we also have neural control neural control this is in response to an optic transmission so a neuron fires at a synapse and the synapse happens to be on the endocrine cell and so it's a direct order basically from the nervous system to release your hormone we have one wonderful example of this that we've talked about a few times here and we could think of the adrenal medulla remember that is directly innervated by presynaptic or pre ganglionic neurons of the sympathetic nervous system and when synapse fires on the neuro secretory cell of the adrenal medulla that neural secretory cell is a endocrine cell it releases epinephrine and norepinephrine in the bloodstream the third category here is what's diagrammed on this diagram and this is called a hormonal control hormonal control all right so release is a response to another hormone so if we come over here and look at this diagram green arrows are stimulatory Reds inhibitory that's what it's going to pay attention to the green arrows here look at what we've got up top here up here we have the hypothalamus all right that's part of the brain you learn at lab hypothalamus is connected to the pituitary by the infundibulum and look what we have here we have hormones being released by the hypothalamus and they're coming down to the anterior pituitary and these hormones are called releasing hormone all right so I'll write a few these down for you but like CRH GnRH trh you're gonna learn these in lab and these releasing hormones they come down to the anterior pituitary here and they cause the anterior pituitary to release other hormones these hormones are called tropic hormones these go onto the bloodstream and where they go they go to a target cell and that target cell is another endocrine cell somewhere in the body it could be a thyroid cell could be an islet cell of the pancreas could be a testicular cell and ovarian cell anywhere in the body where you have endocrine tissues they're getting hormones from the pituitary they bind to the target endocrine cell and cause it to release another hormone and this is our terminal hormone here so what do we have let me draw it this way it's effective purple so we have the hypothalamus oh I got purple okay and that goes to the anterior pituitary and that goes to an endocrine gland I ran out of space let me see here so the hypothalamus here this sets loose or release ER or a releasing hormone that goes to the anterior pituitary the anterior pituitary let's loose with a tropic hormone that's not tropic as tropic and then the tropic hormone goes to the endocrine tissue and causes the endocrine tissue to release well this sage is just a generic hormone so the releasing hormone goes to causes the tropic hormone to be released which causes the hormone to be released which goes to the terminal tissue that right there in purple and red is called a hormone pathway this is terribly common and most of what you're going to learn in lab are the hormone pathways the major hormone pathways they start in a hypothalamus I start in the brain the brain causes the anterior pituitary to release a tropic hormone and the tropic hormone causes an endocrine gland to release the terminal hormone and that goes to its tissue target tissue this is a hormone pathway I'll write that in hormone pathway you can learn these in lab the major ones I hypothalamus has the releasing hormone anterior to eteri has the tropic hormone an endocrine gland has the terminal hormone and that goes to the terminal tissue all right so there's your and your basic vocabulary there now let's go look at the next slide if we look at this slide don't don't be scared this is actually a visual look at many of the pathways you're gonna learn in lab a couple of things point out see this this example right here there's the adrenal gland the adrenal medulla okay so there's your there's your neural pathway right there's an example of neural control over the secretion of hormone for us if we look at this box right here this is where we have our releasing hormones releasing hormones from hypothalamus and they come down the infundibulum into the anterior pituitary and then the anterior pituitary lets loose with ECT h TS hg h PR FSH LH ACTH adrenocorticotropic hormone TSH thyroid stimulating hormone GH growth hormone PR l prolactin FSH follicle stimulating hormone LH luteinizing hormone and you're like oh my gosh what's he doing to me well you're gonna learn these in lab so all of these here right these are tropic hormones now these tropic hormones they go out to endocrine tissues somewhere out in the body and then those endocrine tissues produce terminal hormones right so these are the actual hormones that end up impacting target tissues so this this is a look at our major hormonal pathways the direct release a hormone example over here from the hypothalamus is a little bit different so you learn about the posterior pituitary pathways is the patterns just a wee bit different so you don't have to learn this for class now this diagram is not going to show up on an exam or anything like that it's just wanted to give this to you to give you context for what we just talked about on the previous panel and to give you a heads up for the type of things that you will learn in the lab when you do the endocrine lab here this diagram this is kind of fun I wanted to give you a heads up here on lab again this this is more of a conceptual thing and I could teach you a little bit of anatomy and it will give you a give me an idea here about you know some special aspects of circulation that can occur in the body think about these releasing hormones that are going to be dumped into the bloodstream by the hypothalamus and they are supposed to go to the anterior pituitary and cause the anterior pituitary to release tropic hormones into the bloodstream so that's you know what we're kind of looking at here we've got the hypothalamus up here you've got the anterior pituitary here right so I'm gonna take those off just give me some orientation air alright so we've got the hypothalamus and the anterior pituitary you know type analysis is supposed to dump hormones into the bloodstream and then the hormones go to the anterior pituitary I want you to remember your basics of circulation so if we have a blood vessel all right you know in an artery right and then that artery branches into a capillary bed and then that capillary bed you know services of tissue gas exchange in there and you do a tree in exchange and you bring co2 out and waste products out and then you come back into a vein and remember here's your direction of blood flow you come from the artery you go through the vein and what happens when you leave the capillary bed in the vein you go back to the heart and you have to go back to the heart to the right atrium into the right ventricle and then you go through the pulmonary circulation roots as lungs back to the left atrium to the left ventricle out through the aortic arch and then you can go back into arterial circulation and maybe just maybe you end up in the anterior pituitary that is called the scenic route right and it would be ridiculous for the hypothalamus to release and I'll show you the pathway or follow the bouncing hormone right it would be ridiculous for the hypothalamus to release a hormone and where it would be here actually let me back up just a little bit here this capillary bed this would be the hypothalamus so it would be ridiculous for the hypothalamus to release a hormone here and have it go all the way back to the heart before it could come back and target the anterior pituitary that's less than a centimeter away so we wouldn't want to do it that way we would not want to take the scenic route around the body to target a tissue that's a centimeter away so what we have here is a different way of routing the blood flow so we start here with an artery that artery goes into a capillary bed and then into the vein okay and then we'll say there's the hypothalamus there's the capillary bed of the hypothalamus the hypothalamus is going to release this hormone and that hormone is going to go out to the vein and then what's going to happen here is in this case the vein enters a new capillary bed and that veinous capillary bed once you pass through that venous capillary bed you go back to the heart and on this diagram the second capillary bed there's the anterior pituitary so what we have here is two capillary beds in series one right after the other and we call this a portal system most people if you pull on their toenails they'll admit they've probably heard of the hepatic portal system yeah and that's probably the the most well-known one but here we have the hypothesis portal system now hypothesis let me write this down this is the high puff Fasil portal system the hypothesis here refers to the pituitary gland that's an old-school term for pituitary alright so this is the hypothesis or ttle system if I take this this example here of the two capillary beds in series the hypothalamus first capillary bed this vessel in the middle is called the portal vessel and then here's the anterior pituitary capillary bed let's come over here on the diagram and see this one right here there's the hypothalamic capillary bed this one right here this is the anterior pituitary capillary bed and what we have right here there and there they're showing these are the portal vessels so there's your hypothesis or ttle system you have one capillary bed with the artery coming in you have the hypothalamus dropping releasing hormones into the bloodstream here those releasing hormones go directly to the second capillary bed of the anterior pituitary and that is um once once these cells get hit by those releasing hormones they dump tropic hormones into general circulation they go back to the heart what you're going to notice on here and I won't spend a whole lot of time here but the posterior pituitary here the posterior pituitary has its own blood supply it has a traditional capillary bed like the top diagram on the left you have arterial blood come in you have one capillary bed and you have one vein coming out so the posterior pituitary operates differently from the anterior pituitary all right this diagram is our our old friend the G protein complex and this is important when we talk about hormone action and in fact usually in a EMP textbooks they introduced formally G proteins in the hormone chapter and that's what this diagram represents is they're using a hormone example to show you how a G protein complex works and to review we'll take my little laser pointer here and remember here's the hormone it has a receptor on the membrane potentially they combine that hormone it's going to be specific for that hormone now if this protein receptor is part of a G protein complex then what's going to happen is when the hormone binds to the receptor that is going to activate a G protein complex on the underside of the membrane in this case the hormone typically doesn't cross the membrane it just binds of the surface receptor and that activates the G protein in the parlance of G protein systems the hormone here or what we would just call the signal molecule that is called the first messenger and they they talk about this over in the text once that G protein complex is activated follow the gray arrows there's a couple of choices here the G protein is going to go into the cell and cause something to happen inside the cell one choice path over here is that G protein can have an impact on what's called cyclic a MP levels cyclic adenosine monophosphate so it's a one phosphate version of ATP and this is a common signal molecule inside of cells so in these cases these two boxes over here you see cyclic a and P on this side and cyclic AMP e on that side cyclic a.m. P axis what's called a second messenger so the hormone is always the first messenger in this case cyclic AMP E or here in these two cases cyclic AMP e is the second messenger and now cyclic AMP E is a funny thing it is typically used to up regulate metabolic activity in cells so on this left-hand box example when the G protein gets activated it takes ATP and converts it to cyclic A&P and the cyclic AMP e goes to work and in this level when cyclic GMP increases enzymes are activated and metabolic activity increases over here cyclic AMP E is still the second messenger but the G protein is deactivating it is turning cyclic GMP off when this happens you shut things down it down regulates cellular metabolism so when we're talking about a G protein complex and cyclic a and P is the second messenger it could either have off regulatory impacts or down regulatory impacts the other really common second messenger here is calcium calcium ions are considered second messengers in this case the first messenger hormone binds the G protein complex is activated and that causes calcium to flow in because it opens calcium channels calcium binds to a kinase here called calmodulin and that activates enzymes in the cell this calcium calmodulin complex as a second messenger system is always up regulatory it's increasing metabolic activity of the cell so here's some common you know hormone receptors G proteins and gives us an idea of some comparisons for how these work now on the next panel I'm going to put up a section of our lecture outline and I'm gonna help you fill this in follow me along here though there's some interesting variations here right if we talk about some of the g-protein mediated hormones like catecholamines protein peptide hormones these polar water soluble hormones they you know they use this system alright so I'm going to write this in over here somewhere so polar water soluble hormones and again on the next panel we'll write some of this down because they're polar they can't cross a membrane so they can only you know stick on the outside and then they can cause the g-protein activate and do protein does the dirty work on the inside but there are some interesting variations eicosanoids if you go back and you look back at the big diagram we studied to look at the structural of hormones the amino acid biogenic a means the peptide hormones and the lipid derivatives the eicosanoids were one of those lipid derivatives those paracrine factors their lipid derivatives right which means they can cross membranes without any issues but eicosanoids still use g proteins well what's up with that if I use my little purple pen here on our diagram and follow and eicosanoid hormone on on this this eicosanoid hormone which is lipid soluble and can cross the membrane it'll actually cross the membrane it'll come in and it'll bind to the receptor on the inside of the membrane and then activate the g-protein so it still uses a deep protein system but it's lipid soluble it crosses the membrane first binds to that receptor but on the inside of the membrane and then activates the D protein it's kind of cool so I just wanted to kind of throw that in there onion so this is a portion of the lecture outline that applies to that G protein diagram we were just talking about so let's let's do a few things here to help you organize this so when we talk about the receptors up here we have the membrane bound receptors the G proteins okay that's all of these that you see here so G proteins now the hormone types that use the G proteins so we change the color here keep the catecholamines and the peptide hormones for example all right these are water soluble so that means they're polar they can't cross membranes right so these bind to the external receptor and then activate the g-protein from the outside okay the eicosanoids here these are lipid soluble right these are derived from fatty acids right so these are nonpolar they can cross membranes freely but they see eicosanoid still used you proteins right so these cross the membrane and bind to the receptor internally and activate the g-protein from the inside all right and then we talked about the the the messengers the second messengers the first messengers are always the hormones okay these are the these are the I gotta get my pen back here these are the first messengers now the second messengers down here so we had cyclic a and P here and recall with cyclic ampere either the g-protein is either turning it on or turning off so this can be either up regulatory or down regulatory they can devote Cabul areas and last chapter was excitatory or inhibitory right up arrow is excitatory down arrow is inhibitory and with calmodulin calcium complex these are always excitatory or up regulatory the last thing here you see is intracellular enzyme Cascades this is what G proteins do is they generate intracellular enzyme cascade so intracellular means inside the cell enzyme Cascades so I have a diagram I want to show you that illustrates the idea of an enzyme cascade so here's a diagram that shows an enzyme cascade right what do we got here we have the hormone the first messenger we've got the receptor right and then on the inside we have the activated G proteins alright so remember this is schematic I mean it is trying to illustrate a concept to you but one hormone for example activating one receptor which activates on this diagram 3G proteins all right so you got three G proteins activated whatever and then we have a dental e cyclase which is the enzyme that turns on cyclic AMP II all right so cyclic AMP E is our second messenger cyclic a and P is acting like an enzyme right it's an enzyme activators really what it is so here's our second messenger and then what cyclic AMP e does is it turns on other enzymes and that's every level here is multiplicative if we say so if we follow the bouncing ball here you know a few activated G proteins can turn on a bunch of adenylate cyclases which can turn on a bunch of cyclic AMP E which can turn on a bunch of protein kinases which then can go on and do a whole lot of work inside the cell and this is a cascade so this is a molecular way to take a very small signal up here and generate a very large effect down here with one hormone molecule it's an enzyme cascade and this is how hormone signaling works when you use a g-protein now this diagram shows the other pathways by which hormones can impact cellular activity and these are intracellular receptors what I want you to notice on here is wherever you see these little green boxes there - on the left - on the right those the receptors for the hormone so if you look at that like the receptors are not on the external membrane the receptors are inside the cell so in order for these hormones to do their jobs they actually have to pass into the cell and then find their receptor protein and then once they bind to the receptor then that causes cellular changes so there's two general pathways here by which hormones combine two intra cellular proteins or receptors the one on the left here get steroid hormones so testosterone androgen estrogen estradiol progesterone things like this the steroid hormones remember they're all derivatives of cholesterol and are all nonpolar so they can freely cross membranes so if you now follow the follow the bouncing hormone here there's your steroid hormone number one it just diffuses into the cell when it does this what we find is that there are a couple of different choices where it is going to find its receptor one here is a cytoplasmic receptor or it could travel all the way through the nuclear pores and inside the nucleus and find a nuclear receptor see God you know both things could happen the same hormone could bind in both places but I think there's either one or the other now in these cases if it's a cytoplasmic receptor here what is going to do is just going to you know generate some sort of intracellular enzyme cascade - starting here if it's a nuclear receptor what it's going to do is it's going to cause a change in gene expression typically you're going to be activating genes creating new messenger RNA transcripts creating new protein products and that's what's going to cause the cell to respond differently that's the job of the hormone in this case is to turn on genes or in some cases turn them off alright so you know you could have target receptors in either the cytoplasm or the nucleus for different purposes so these are the steroid hormones on the left on the right here we have thyroid hormones thyroid hormones so this is going to be t3 and t4 are your basic thyroid hormones now the thyroid hormones these are water-soluble they're they're polar these are derived you know from tyrosine these are biogenic amines these are modified tyrosine amino acid molecules so they shouldn't be able to do intracellular receptors because they can't cross membranes and that's true but what cells have virtually all cells have thyroid hormone transporters on their surface so look at you know follow the bouncing hormone here and step one transport across the plasma membrane these are t3 and t4 transporters and there have been at least 20 different thyroid hormone transporters identified on various cells in NEMA body there's a bunch of them out there so when these thyroid hormones show up they make their way into the cell and again they have two different options they could have a cytoplasmic receptor or nuclear receptor in the case of the nuclear receptor you just alter gene expression produced new proteins and all that the cytoplasmic receptors are on mitochondria a thyroid hormone they regulates your basal metabolic rate and so when more t3 and t4 comes into the cell and locks onto the mitochondrial receptors you increase ATP production and what that does is that it turns up the activity of the cell that's how I rate hormone works so here I'll take all this mangled drawing now and I'll help you on the next panel turn that into some notes on your lecture outline okay so here we are towards the very end of your electrolyte and we're in the last panel so we just talked about intracellular receptors and we started with a steroid hormone so we said hey there lipid soluble these are nonpolar these these freely cross the membrane or diffuse they combine two cytoplasmic or nuclear binding receptors but they often act as transcription factors and they cause genes to be transcribed at various rates inside the nucleus then we we had the t3 and t4 the thyroid hormones and these are water-soluble so these are polar they can't cross membranes by themselves but these are transported across the membrane and then bind to intracellular receptors both cytoplasmic and nuclear so their cytoplasmic receptors are on mitochondria there are nuclear receptors act as transcription factors so the mitochondrial binding increases ATP production and increases the metabolic rate of the cells and most of the cells in your body have these III and t4 sort of plasma receptors so and you increase the circulating rates of our circulating titer of thyroid hormone then generally speaking all the cells in your body operator to higher metabolic rate and when you lower the thyroid hormone circulating level then generally speaking all of your cells start operating at a slower metabolic rate so there you go there's a I don't know a not so quick tour of the functionality of the endocrine system all right you can learn specifics of hormones and normal pathways in lab but this gives you a broad overview of how the system works all right talk to you soon