Glucose homeostasis lesson 1, Glucose control and insulin

right by homeostasis you know about homeo means the same and stasis literally means standing so it means of the same standing or in the same situation homeostasis and you know that there's many parameters in the body that need to be homeostatic ly regulated not too much and not too little so it's a bit like Goldilocks is porridge isn't it not too hot not too cold so got to be just right because human cells and human tissues are very particular about the conditions they live in and one of the parameters that needs to be tightly controlled is the amount of glucose in the blood glucose is the sugar found in the blood now we eat all sorts of carbohydrates and we all sorts of sugars so you might have heard of sugars like galactose or fructose where are the simple sugars but all these are converted into glucose by the liver so whatever sugars absorb from the GI tract it's always glucose in the blood just miss my video you realize your profiles would be on YouTube that's a clock you don't do from sin right so all the sugars in the blood are converted into glucose that is the sugar in that was always glucose so when people talk about sugar they always mean blood glucose and give or take roughly aunt it's between 4 to 8 million models per liter of blood that would be kind of roundabout the normal level now if you've been out on the fells the long walk and you've been working out and you have plenty of exercise and you haven't done much to eat it may go below for a little while but you've just had a meal followed by sticky toffee pudding followed by after apes that in my god Burbank flew to one in normal situation four to eight would be what we would expect and this is important because in diabetes taste with diabetes we don't want the blood sugar to go low of lower than four so what we say in diabetes is four is the floor four is the floor so if some of the diabetes has a blood sugar of lower than four will normally try and get it up a bit we don't want it to be that road now if the blood sugar is not homeostatic Li regulated it can go too high so hyper for high climb for glucose emia fit in the blood high levels of glucose in the blood and we don't want this because when that happens sugar diffuses into the body tissues and messes them up the body tissues become a bit like you know that crystalline pineapple stuff you get the taste really nice but its crystalline because it's full of sugar we don't want that the damaged body tissues if the bud is too high this is why we get a lot of long-term complications in diabetes so patients with diabetes are chronically hyperglycemic if the blood sugar is high over many months and years then they're more prone to quite a few of the long-term complications of diabetes so we don't want the blood sugar to be too high if the blood sugar goes low the blood sugar goes low hypoglycemia emia and the blood if it goes low that's bad news as well because as you probably know in all the cells of your body you have a nucleus and you'll have a few hundred to a thousand or two of these sausage-shaped organelles these sausage-shaped structures remember these ones and then enfold it in a membrane yeah the mitochondria which are the powerhouses of the cell all the energy that cells make is made in the mitochondria we don't get any energy from other sources and all living processes need a constant supply of energy to fuel the life-giving processes we always need the energy so what happens in cells is that glucose combines with oxygen glucose and oxygen and it's that which produces energy the glucose is burned in the oxygen to give us the energy and as you probably know at the same time this results in the production of water and carbon dioxide this needs to go on inside the cells to produce the energy and obviously we're hypoglycemic there's not going to be enough sugar to do that not enough energy now that's okay for some tissues some tissues can work without glucose it can use fats we can use fatty acids as their fuel supply but the brain is not very good at that the brain is an obligate glucose user the brain has to have glucose so if someone becomes hypoglycemic the brain can't produce energy in the mitochondria therefore the brain stops working and make no mistake about it these people will die hypoglycemia is a life-threatening condition so we always have to be careful how we use insulin because if we give too much page it's become hypoglycemic and there is a real risk that they're going to die because their brains will stop producing energy can you see why poor is the floor you're not going to die with a blood sugar of two you don't feel good very good but can you see us on the way down and below that you are getting to very very dangerous levels indeed that's why we say four is the floor we don't want to go lower than before right hypoglycemia causes long-term complications over weeks months years but potentially over days if your hypoglycemic you're more prone to infections straight away and things like that but most of the complications are very long-term with hypoglycemia whereas hypoglycemia can kill you in half an hour yeah that's a very good question the answer is probably yes yes yes the answer is probably but the evidence through it is not strong but the patient's feel so bad we want to avoid it anyway but yeah through chronic chronic hypose yes probably does have some long-term Dilla Terius effect but it's not well evidenced to feel normal again mmm-hmm yeah yeah yeah I mean it's not really something to be overly concerned about in long-term complications but it probably is something but it will follow a distribution curve the same as everything else you know some people have them and not have adverse effects some people have them will have adverse effects yeah yeah yeah yeah the main thing with hyperglycemia is that you we a lot that's the main immediate feature you get what you call an osmotic diuresis yeah because you're dehydrated yeah yes osmotic diuresis yes when the sugar goes into the nephron it attracts water because the glucose is osmotic so you can wheeze huge amounts and of course that makes you chronically dehydrated and that makes you chronically thirsty and the other thing that happens is if the mitochondria can't use glucose for their fuel supply in the muscles of the body then they have to use something else and there's something else the uses are fats and proteins so you get weight loss so that's the classic triad for the presentation of diabetes those three things polydipsia polyuria and weight loss any of those three we should automatically do one of these new dance and test the blood glucose levels yeah right okay yeah yeah well we type - you certainly get hyperglycemia with type-2 diabetes the the reason that you're more prone to hypoglycemics with type 1 is not because of the diabetes that causes hyperglycemia it's because of the insulin its the insulin that lowers the blood sugar levels dramatically as hopefully we'll see now with type 2 some patients with type 2 diabetes do take insulin therefore their risks of hypose are just the same as someone with type 1 more typically patients with type 2 diabetes take oral hypoglycemics they take oral medication to lower the blood sugar levels now some of those like little as I can lower your blood sugar quite dramatically others like metformin I supposed to lower your blood sugars dramatically but actually they do people that take met foot the book say they don't like the people that take metformin for type 2 diabetes do have high posts and they do feel pretty bad now they're not crashing hypose like you would get with ensuring they're not going to die from it I don't think but they certainly get hypose but with with some of the other hypoglycemic like gliclazide you can get you can get quite bad hypose yeah so so the answer is that that met form is not supposed to cause hypose but it does hmm yeah excellent questions good yeah so anyone who's weighing a lot thirsty a lot or losing weight and that hasn't got an obvious explanation then we need to start thinking about their glucose status and of course it's very simple to test the glucose levels in the blood so we don't want hyperglycemia we don't want hypoglycemia we don't want hyper or hypo what we want is what we want is you glycemia you glycemic means that the glucose levels in the blood are normal that's what we want we want them to be you of lice emic can you see why this is a homeostasis outing isn't it don't want - oh hi phones we want you glycine so how is that tuned well some of you have come across this one before remember him poor her pancreas now the pancreas is described as an organ with a head the body and a table and it's here put you hands up them right so the head of your pancreas is there towards the middle and right side and then the body is over there and the tail is over there so it's a head a body and a tail of course what most of the pancreatic cells do most of the pancreatic cells produce digestive enzymes so these ducts here these pancreatic ducts digestive enzymes go down here come out here and of course that goes into the first part of the small intestine which is the QED there's a few bile ducts too complicated for that's basically what happens that's good because it means you can digest proteins it means you can digest fats means you can digest carbohydrates thank yous produces all sorts of digestive enzymes which of course is fairly boring but what is very interesting about the pancreas is it's very spotty distributed throughout the parenchyma throughout the tissue of the pancreas there's lots of these little islands of tissue and when you look at the mini microscope it's like you're flying over a sea of pancreatic cells and then from time to time you're seeing these little islets these are called the pancreatic islets and if your how I don't know should say about 35 voiceover you probably learned the term the pancreatic islets of langerhans of course you may be young in know about the pancreatic islets of langerhans action teacher like me so the pancreatic islets or the pancreatic islets of Langerhans is a guys named Paul Wang and Hamilton gives them yeah that's these dots well Lana hadn't discovered these pancreatic artists and said Arvin call them the pancreatic islets on one hand it's been like Stanley walking through Africa I think we'll call this Lake Stanley in them leave it isn't there perhaps what maybe wasn't it maybe it was his mates thought it was a good idea now there's about one and a half million of these little islets in your pancreas about one and a half million of them so the loads are these things but they're very small pancreatic islets now if we look at one of the islets magnified a bit that imagine that's a pancreatic islet then we find that there's two main types of cells in pancreatic islets right about the outside this type of cell called alpha alpha Sellars that's a Greek letter alpha so the Alpha cells around about the outside of the pancreas primarily but there's more cells inside called beta cells that's the Greek letter beta so as alpha cells around the outside of the pancreatic islets and beta cells in the middle of the pancreatic islets and between the two of them these are the main cells that control the amount of glucose in the blood so first of all let's think what happens if the glucose levels start to rise so you have something to eat the carbohydrates and the sugars are digested to go into the blood blood sugar level is going to rise and the beta cells have a good blood supply so the beta cells are able to sample the blood which is going through the Vita cells they can sample that blood and the beta cells are so clever they can detect when the amount of glucose in the blood has gone up in other words the beta cells detect hyperglycemia they detect increases in blood sugar level so when the blood sugar level rises that's detected by the beta cells and in response to that in response to that the beta cells produce insulin so in the blood sugar level rises is detected by the buter cells and the beta cells produce insulin so can you see now as well as having a lot of sugar in the blood we've got insulin in the blood as well because the pancreas or the digestive enzymes in the pancreas leave via these ducts and anything that produces product which leaves by a duct is called an EXO crying glad you had that of EXO to exit so if the product leaves via a duct we call that an EXO crying product because it is exiting the gland but the insulin is not like that the insulin doesn't leave the pancreas via duct it leaves the pancreas via the venous drainage of the pancreas it goes straight into the blood and whenever a product is released straight into the blood the term we use for that is endo craft so the beta cells are endocrine they are releasing the hormone insulin directly into the blood so we've now got more insulin in the blood which is good so what well the glucose is a simple molecule glucose is actually only c6 h-12 o-6 so a glucose molecule only contains 24 atoms quite a small molecule and it's this kind of shape it shaped like this so hexagonal shape and glucose is a highly soluble molecule it's highly soluble because it's small its water soluble it dissolves in the water brought tissues of the body and because we've just added something to eat it contains carbohydrates we've got loads of these things glucose floating around in the blood glucose floating out in the tissue fluids lots of glucose molecules now what insulin will do one of the things that insulin will do is it will tidy all these individual glucose molecules up so the first thing it will do is it will tie them all together into a big long string hundreds of Units long it ties them all up into a big long string and that big long string that polymer is a polysaccharide of glucose molecules it's a big long molecule like starch the glucose is converted into glycogen so this is called glycogen so the glucose is converted into glycogen big long polysaccharide molecule and what the body does is it stores this glycogen and it stores it in two places primarily it stores it in the liver and it stores it in the muscles so it's stored in the liver and in the muscles so if all these glucose molecules are now forming a glycogen molecule can you see all the glucose molecules are no longer in the blood they're all neatly tied it away in relatively insoluble form and the stored in the liver and the stored in the muscles what's that going to do to the amount of glucose in the blood it's going to reduce it isn't it so can you see the initial problem was hypoglycemia that hyperglycemia was detected by the betta cells and the pancreatic islets of the pancreas as a response to the hyperglycemia the beta cells produced insulin the insulin facilitated the conversion of glucose to glycogen he took the glucose from the blood and tissue fluids converted it into glycogen and swept all that away neatly into the pan into the liver and the muscles therefore the amount of glucose left in the blood is reduced that's one thing the insulin does that's one of its hypoglycemic mechanisms one of the ways it lowers blood sugar levels and that's also quite a neat trick because we've just had something to eat today but you think there'll be any food tomorrow well yeah obviously because of the packet of biscuits in the cupboard isn't there but of course there might be no varies or foraging crops available tomorrow maybe the young men won't make anymore kills for the next month so in a basic tribal situation can you see it's absolutely vital well anytime where there's not enough food readily available or necessarily available it's absolutely vital if you store it up for the next couple of days whenever we can and that's what the body does it stores it but it also gets rid of it so we're not getting the complications of hypoglycemia we can you see heredity that if someone has diabetes if someone type one diabetes what actually happens in type 1 diabetes is the beta cells are actually destroyed in type 1 diabetes the beta cells are destroyed by the body's own immune system it's a terrible mistake it's called an autoimmune disease so type 1 diabetes the sugar can go as high if you like and you'll get very sugary blood going through the pancreas then of all the beta cells are dead can you see there's nothing to detect that hyperglycemia and there's nothing to produce the insulin to combat that high both hypoglycemia that's the problem it's a terrible mistake the immune system over the course of a couple of years completely destroys all of the beta cells terrible mistake but that's what happens now what we have lying around inside cells as well as the mitochondria lying around inside cells there's doughnut-shaped structures for pollo mini shape structures not like a jam donut you know poppy donut with a hole in it so they're lying around inside inside cells and also on the surface of cells there's a special protein and that protein is an insulin receptor so there's insulin receptor proteins on the surface of cells so when the blood sugar is too high in the normal situation the beta cells are going to release insulin now insulin is a molecule with a particular shell let's imagine it's around it's actually a short protein is made up of a chain of about about 51 amino acids so the engine has been released and we know that the insulin has already facilitated the conversion of glucose to glycogen but also the insulin fits into the insulin receptors on the surface of many cells so the insulin fits onto the insulin receptors this is the lock and key idea isn't it so the key would be the infant molecule and that's fitting into the lock which is the insulin receptor so that fits into there which is all very nice and snug but when insulin fits into the engine and receptor actually this insulin receptor goes all the way through the cell membrane to the other side it's actually what you call a transmembrane protein it goes all the way through and when the insulin combines with the insulin receptors these this combination sends messages off to these pollo mint shape molecules that are lurking around inside the cytoplasm of the cell well the Polo milkshake ones are actually called glute and that stands for glucose transporters they're called glucose transporter molecules but at the moment they're not that completely useless because they're inside the cell sitting around doing nothing inside the cell but when the message comes that the insulin has arrived in the Eastern receptor that message goes inside the cell and it sends these doughnut shaped molecules these paolo ship shaped molecule polar man shaped molecules to the cell surface so what you end up with is one of these round molecules with the hole in it on the cell surface so it floats on the cell membrane on the surface of the cell and what that means is that these individual glucose molecules that are kicking around the earth should go back a bit before these glucose molecules arrived so I before the glucose transporter molecules arrive the glucose molecules would try to get into the cell they would try to diffuse into the cell but the problem is they can't because the cell membrane won't let the me why won't the cell membrane let the glucose molecules in because after all the mitochondria needs the glucose molecules to get in they're not too big relatively small molecules yeah that's right that's right the answer is that the cell membranes are made of lipids some membranes are made of fat basically cell membranes are made a fuss fold it's and that means that the water soluble glucose molecules can't diffuse through the fatty cell membrane because fats and water don't mix so you know if you've got some water and you pour some olive oil in it it just forms globules doesn't it doesn't mix so because the glucose molecules are water soluble they can't diffuse the the fatty cell membrane stuck on the outside but now can you see a hole has arrived that makes sense the hole has arrived and that hole is sitting on the top of the cell membrane so now the glucose molecules can get through the hole that is the glucose transporter molecule into the cell going to the mitochondria where they are required you need the glucose to trance you need the insulin to transport the glucose into the cells before that the glucose waited without while the nitric Andreea waited within without glucose so the glucose was outside couldn't get in even though the mitochondria wanted it glucose couldn't get in until this hole was provided by the glucose transporter molecule but that only happened because the insulin hooked up to the insulin receptor now as a result of this the glucose will pour through the glucose transporter molecule into the cell and the mitochondria will be happy they'll make all the energy they need now this is the great irony in diabetes in diabetes type 1 anyway when you don't have the insulin you don't have the incident you've got these glucose transporter molecules inside the cell doing nothing you've got this massive glucose outside you've got great hyperglycemia outside you've got no glucose inside so you've got masses and masses of glucose outside no glucose inside so you've got the glucose outside causing the complications of hyperglycemia but you've not got no glucose inside to fuel your metabolic processes so the mitochondria supplies to use fat and proteins to make its energy you need the interesting to get the glucose into the cells so can you see now we've got loads of glucose inside the cell much less glucose in the blood because the glucose from the blood has gone into the self therefore with lower blood sugar levels that make sense no no the gate goes through as individual soluble glucose molecules so there's two separate mechanisms via which insulin is lower and blood sugar level one is it forms these big long strings of glycogen and stores them away for tomorrow the other one is it transports the glucose molecules through the cell membrane into the cytoplasm of the cell so it's two completely separate mechanisms but they both have the same effect they both lower blood sugar levels and when you give insulin blood sugar levels are lowered quickly and dramatically this is a very effective mechanism so the original problem was hyperglycemia the blood sugar blood sugar was rising because we'd eaten so the insulin brings it down via those two mechanisms so as a result of the production of the insulin can you see we can now restore you glycaemia as opposed to having ongoing hyperglycemia you want to tell that story to you next-door neighbor

Channel: Dr. John Campbell

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Keywords: homeostasis, blood sugar, blood glucose, insulin, diabetes, live lesson, human biology, physiology, nursing, nurse eduction

Id: xGtcUQKt1q8

Length: 35min 56sec (2156 seconds)

Published: Tue Mar 18 2014