okay welcome to bio 228 um I hope you've had a chance to get on the canvas site and find what you need so far um if you have any questions about that whatsoever please let me know by email or on my phone and we can get on a zoom call and I can I can show you around um that's no problem um anyway this week we're starting with the endocrine system and we're going to continue with the endocrine system next week but we'll just kind of get rolling so what I'd like to do right now is I'm share my screen and let see okay here we go so the endocrine system the endocrine system so we will go through all of the systems of the body um that you didn't cover in 227 yet um the semester and we are starting with the endocrine system which is made up of hormones in the body and the glands that secrete them so this is a little bit different of a system compared to things like the digestive system which are comprised of like a bunch of different organs and then a specific function like digesting your food or the respiratory system which is composed of again the very specific organs and one particular function this is different it's composed of glands that are dispersed all over your body the hormones that that are secreted by those glands and then the effects of those hormones are so diverse and varied so this is a slightly different system in that way um in each of the lectures that I give I'll always have this learning outcomes slide posted for you both at the beginning and usually I think um also at the end as well this is just a place for you to come back and kind of check yourself off like okay I listened to the whole lecture I took some notes I did some studying do I understand everything I need to understand and you can come back here and kind of check yourself off and if there's something on this list that you um you know find that you don't remember or don't understand fully then that's your kind of clue to go back into the lecture listen again um or in some other way try to get yourself up to speed um and I'm always here to help you with that okay so that's here for you um let's begin um the endocrine system or Endocrinology so again the endocrine system is made up of hormones and the glands that secrete them and you can see in this little picture over here which is stirred out of your textbook um that these glands are scattered throughout the body they are generally made up of the hypothalamus which is in the brain the pituitary gland is attached to the hypothalamus by this little stock we call the infundibulum um so those two glands are attached to each other and do have interplay between each other and which I'll explain and then there's the pineal gland in the brain so these three um these first three on the list are housed in the brain the adrenal gland sits right here on top of the kidney it's this little pyramid shaped gland these are your kidneys adrenal glands are attached on top the thyroid gland is this butterfly shaped gland in your neck um the thymus gland is right underneath that right inferior to it the pancreas is here and the way that this pictures the pancreas and my mind isn't super accurate the pancreas is a little more Superior and it occurs behind the stomach so they're just not showing the stomach in this picture there are if you were to dissect the pancreas out you would first see that you would open up the ab abdomen and you would see the stomach and you could see a piece of the pancreas um not hidden by the stomach but most of it is behind the stomach um and then where are we ovaries and testies are the last on the list so we're going to talk about each of these glands the hormones that they secrete and the action of those hormones in the body um that's kind of where we're headed what we want to understand is that each of these glands has a very rich capillary Supply like blood supply each of these glands is just basically surrounded by um blood supply and the way the endocrine system works is that the gland um makes the hormone and then the hormone is released from the gland and then um so it diffuses across the cell membrane of the gland out of the gland from there it diffuses into the blood right away because the gland is just encased in blood supply so the hormone moves out of the gland into the blood now it has access to the whole body so the blood carries that hormone to every single cell in the body certain cells are affected by certain hormones but not by other hormones so we call the cells that are going to be affected by a hormone a Target cell let's look let's talk about it with an example in mind because that's much easier um let's say we're talking about the pancreas and the pancreas secretes two hormones we're going to talk about insulin it's a really important hormone and then the hormone that has the opposite effect which is glucagon so let's just talk about insulin for a second so you can here's the pancreas and they're not showing blood supply in the picture but you can picture in your mind blood supply just like all wrapped around the pancreas and so insulin is secreted by the pancreas made by the pancreas then released from the pancreas then is absorbed into the blood and now the blood is going to have carry that insulin all over the body every single cell now has access to insulin however only certain cells have um cell receptors for insul so if a cell um does not have let me draw this for you let's say so we're looking at the pancreas and let's just make a bed since we're talking about blood right there's blood supply like wrapped all around um the pancreas and so then insulin and then the blood supply goes everywhere which this is going be a bad picture of that but every cell of the body now has access and down the legs to insulin all right so blood is going to carry this insulin all over the body now let's zoom in on a particular location in the body and blow it up so here's our blood supply right um all the things are flowing through the blood including insulin which I'll draw in something different let's say so let's say these little blue guys are our insulin molecule and they're carried all over the body and then we've got cells draw the cells in green just because they're different right um okay so some of these cells have no cell receptor or receptor for insulin so insulin flows right by these cells not interested right other cells now I'm going to blow one of these cells up okay let's blow this up here's this cell this is the cell membrane and on the cell membrane there's a cell receptor for insulin let's say it looks something like that right so some cells in the body will have these cell receptors that are specific for insulin and other cells don't right skeletal muscle cells and atopos or fat storage cells have a lot of inin receptors on their cell surface and so here comes the insulin right and a lot of these cells do not have cell receptors for insulin so they're not going to be affected by insulin but the cells that do have receptors for insulin um let's see I'm looking for a different color okay so insulin would diffuse out of the blood and then it would bind to the cell that has a cell receptor for it when a hormone binds to a cell um then it causes a change of action in that cell the cell is now going to be affected by the hormone binding and when insulin binds to a cell what happens is now glucose can enter sugar can enter the cell but every hormone has a different effect on a cell so insulin's effect is to allow glucose in another kind of term that we need to know is that cells that have a a cell receptor are called target cells so insulin's target cells are generally adapost tissue and skeletal muscle um and then you know for other hormones skeletal muscle and adapost tissue don't have cell receptors and there therefore we they are not target cells so every cell in the body has access to these hormones that are secreted but they only actually are affected by a hormone if they have a cell receptor for that hormone and if they do we call them a Target cell okay so that's generally how this works let's sum it up right there are um the endocrine system is made out of these glands and the hormones that are secreted by the glands the way that works is the hormone makes the the hormone the gland makes the hormone the hormone diffuses out into the blood the blood carries the hormone to the body now every single cell then would have access but only target cells are affected by hormones and then would change their activity or action when a hormone binds to their cell surface okay all right okay okay now there's two kinds of hormones there are amino acid based hormones which I'm showing you on this slide and then there are steroid hormones which is a type of lipid um which I'm showing you on the next slide so there are two kinds of hormones and we're going to talk about how each one acts or travels through the body a little bit differently most hormones are amino acid based hormones or protein based hormones proteins are water soluble they will dissolve into water um maybe you remember your 227 teacher or some instructor in your past giving you the rule like dissolves like um meaning a polar molecule will dissolve in a polar solvent water is polar and a and proteins are polar so proteins dissolve in water um and so let's draw so let's say we're talking about a gland doesn't really matter which one here's my gland all right and the gland is making a hormone draw the hormones and B again okay so the gland is making this hormone this amino acid based hormone the hormone is going to diffuse out of the gland cross that membrane it's going to diffuse into the blood okay which is blood supply is all always sitting right outside these glands so now blood plasma is made up of mostly water and we're going to talk about that in the coming weeks but I'm telling you right now blood plasma um is mostly water so blood is watery and proteins dissolve in water great so that means that this um hormone is going to be very easily carried by the blood so it it diffuses right into the blood it dissolves into the blood and it's carried around the body just like that so that is very simple and easy okay that piece of it now let's say um now the hormone arrives at a Target cell meaning here's a cell right that has a cell receptor at this particular hormone that makes this a Target cell for this hormone so in that case the hormone then diffuses out of the blood binds to the cell receptor and when that happens the cell will change its action will there will be like a change in the cell's activity based on the hormone binding so let's blow this cell up a tiny bit again okay I'm just going to increase the magnification if you will let's look at the cell membrane remember a cell membrane is made out of a phospholipid Bayer and the phospholipid bilayer oh this is a I'm GNA get used to my very bad drawings I think I'm drawing with my mouse by the way okay which makes it a little better okay but this is my phospholipid by layer if you remember a phospholipid has a head which is polar and Tails which are non-polar this is polar meaning charged and these are non-polar again writing with Elis hard sorry nonpolar meaning not charged okay and so the f liid B layer organizes itself like this okay and then would continue around the whole cell membrane would be made up of this fos by there I'm only going to draw this one little part of it okay so now this hormone arrives at the cell surface the hormone is water soluble it dissolves in water it is polar the hormone is polar like dissolve like polar things will dissolve in polar things polar things will not dissolve in non-polar things so we know the heads of the fossil lipids are polar and we know that the tails are non just gonna write non so this hormone cannot dissolve in the non-polar tails of the fossil lied Bay and so what happens is this polar molecule cannot move easily not without um help it can't just simply diffuse right across the cell membrane and enter the cell that cannot happen because this polar hormone does not dissolve in the nonpolar tails of the fossil lipids are there polar does not dissolve in non-polar and so because of that the work around is that the cell has these cell receptors on its surface and the hormone binds to the cell receptor which then causes a change within the within the cell okay so that is how an amino acid based hormone causes an effect on the cell it binds to a cell receptor and it does that because it can't just flow across the the phospholipid bilayer and into the cell okay amino acid based hormones this is the way they travel through the blood they dissolve right in the blood because they're polar and the blood is polar so that's easy but when they get to the cell they can't just dissolve right in because they're polar and the tails are nonpolar and so instead they bind to a cell receptor and cause change in the cell again that's an amino acid based hormone so let's look at [Music] how a steroid based hormone or a lipid based hormone um moves to the body so once again draw this same drawing we have a gland and it's making a hormone and these hormones actually let's make these a different color since these are uh no what color haven't I used yet how about this since these are steroid based we'll make them a different color and shape just to make the difference more visual in any case they're still a hormone they're just a type of lipid instead of a type of protein and not very many hormones are steroid based or lipid based most of them are amino acid based and then flow through the body the way I just showed you but there are some that are lipid based and so in this case right there's still blood supply right by the gland and these hormones would flow out of the gland and into the blood okay but here we have our first problem and the problem is that blood is mostly watery and so polar water is polar um and this hormone is a lipid non-polar the rule is like dissolves like so a non-polar hormone cannot dissolve in the polar blood so what happens is it needs help and it gets help um from a protein so there are proteins I'm going to draw it like this there are proteins in the blood that bind to these hormones the protein part is polar so it dissolves in the blood and there thereby can carry the the steroid or lipid based hormone through the blood so this is different than the amino acid based hormone which could just dissolve real easily right into the blood and get carried through the body these lipid based hormones need a little bit of help because they don't dissolve into the polar or watery blood so they get this help by a protein they bind to a protein the protein does dissolve in water problem is solved and now this lipid based hormone can move through the body in the blood okay and so now this lipid based hormone arrives at a cell right here's a Target cell and so the the hormone is released it dissolves out of the blood and it moves towards the target cell let's blow this up and look at what happens here H oh rats okay right okay all right so here's again my cell with the fossil within Bayer so when this hormone shows up at this cell drawing right I'm just going to draw a section of the actual fossil lier and simplify it for the rest of the cell because I'm not going to dry the entire thing but this phospholipid bilayer is what the cell membrane is made out of so it is you know in actuality surrounds the whole cell and here comes this hormone okay it is coming to its Target cell and remember that cells exist in interstitial fluid which is mostly water with a bunch of stuff dissolved in it but it's watery and these the the um phospholipid head is polar and the interstitial fluid is watery so it's polar so these heads of the phospholipids are dissolved into the watery interstitial fluid and these heads are dissolved into the watery cytoplasm okay so when the hormone cytoplasm get ahead of my plasm ah so when the hormone shows up at the cell what it actually sees quote unquote sees it doesn't see the heads the heads are dissolved into the watery interstitial fluid on the outside and the watery cytoplasm on the inside so what this hormone has to deal with or what it sees as it approaches the cell are the tails the tails are nonpolar and this hormone is non it's a lipid non-polar like dissolves like so this nonpolar hormone this lipid based hormone can dissolve right into these non-polar tails and then right into the cell it can easily cross the phospholipid bilayer because it is non-polar and the tails are nonpolar so these steroid based or lipid based hormones cross the fossilid bilayer with no help and enter the cell directly let's recap so these steroid or lipid based hormones they need help traveling through the blood because they can't dissolve into the watery blood the help that they get is a protein that they bind to the proteins are dissolvable in water and so they carry the hormone through the body when the hormone approaches a Target cell it diffuses out of the blood and approaches the cell it can then doesn't need any help to cross the cell membrane and enter the cell so these lipid based hormones actually enter the cell where the amino acid based hormones do not enter the cell they bind to a receptor on the cell surface and this is all based on the properties of being polar or non-polar all right once these hormones enter the cell then I'll take you I'm going to take you one step further once they're in inside they bind to a hormone receptor that is hanging out inside the cell a cell that has these receptors that's what makes this cell a Target cell for that hormone many cells in the body won't have those c those hormone receptors then they are not target cells for this hormone but if a cell has um a receptor for this particular hormone that makes it a Target cell for this one whatever it is okay so two different way two different kinds of hormones amino acid based steroid based these are the ways they travel through the body and these are the different ways that they have action on the cell one attaches to the cell surface one actually crosses the cell membrane and then binds to a cell receptor that's internal okay clear that you will also find these slides throughout my lectures and it's just a time to be able to pause and review um and so I have these for you here if I was you I would pause the lecture right here read these questions go through them do what they ask make sure you understand um these Concepts and then I would play you know press play on the lecture again and move on um okay so now I guess the the last thing I want to say here is that like to to explain what are the possible actions of a cell once a hormone has has bound to it whether it's on a cell receptor or an internal cell receptor right so hormones are in the blood they circulate they they bind to target cells and then what so here are some possible actions of a cell after a hormone binds maybe the cell changes its permeability of of the cell membrane meaning maybe it would build some kinds of cell receptors that it didn't have before and allow certain things to flow in or maybe there are certain cell receptors in place that are then taken out so now certain things cannot cross the membrane so it can change the permeability of the cell membrane what can enter and what can't it can stimulate the cell to make enzymes or other proteins so that would change if like let's say it's an enzyme then the cells then that enzyme would become active and so the cell's activity in in that moment would would shift um so it can activate or deactivate an enzyme it can stimulate or induce the cell to make something it can stimulate the cell to undergo mitosis and many other things the point is it changes the activity of the cell in some way okay I'm going to end this piece of the lecture here um and then there are a couple more pieces to this week one lecture that you'll find in um module one