December 8, 2022

Insulin (/ˈɪn.sjʊ.lɪn/,[5][6] from Latin insula, ‘island’) is a peptide hormone produced by beta cells of the pancreatic islets encoded in humans by the INS gene. It is considered to be the main anabolic hormone of the body.[7] It regulates the metabolism of carbohydrates, fats and protein by promoting the absorption of glucose from the blood into liver, fat and skeletal muscle cells.[8] In these tissues the absorbed glucose is converted into either glycogen via glycogenesis or fats (triglycerides) via lipogenesis, or, in the case of the liver, into both.[8] 

Today we’re going to talk about what is insulin what is insulin and why do we need it to stay healthy so let’s say this is you and you’re going to eat a big piece of chocolate cake which i’ll draw here here’s your piece of chocolate cake and just to be proper let’s put it on a plate so you’re gonna eat your piece of chocolate cake which means you’re gonna put it

In your mouth you’re gonna chew it up and then you’re gonna swallow it so you’re gonna swallow it it’s gonna move down towards your stomach here it’s in your stomach and then from your stomach it’s gonna go into your small intestine which is this thing over here so let me ask you why do we eat why do we eat well one of the reasons we eat is because in food there’s

Energy that we need so we swallow a piece of food and in our digestive tract it’s going to get metabolized metabolized which means it’s going to get broken down into smaller pieces and those smaller pieces i’ll draw here in light blue and the little smaller piece that we’re going to talk about today is something called glucose and you’ve almost definitely heard

Of that before glucose is a sugar and it’s the main source of energy for our body so this piece of chocolate cake here might have carbohydrates it might have other larger sugar molecules than glucose although glucose is itself a small sugar and those carbohydrates and larger sugars are going to get broken down into glucose which will then be absorbed into the

Body so something i’d like to ask you now is what does it mean to be absorbed into the body but what happens is you have blood vessels passing over your small intestine and these glucose molecules in the small intestine are going to diffuse across and into those blood vessels so glucose is going to move from the gut into the blood vessels and that way you get

It into your body so let’s draw over here a larger example of one of these blood vessels that’s passing over the small intestine so as we said little glucose molecules are going to diffuse into this blood vessel and that way they’ll be able to travel around the body through the blood to reach all the different parts of your body that need energy so for example

Let’s say they go all the way up near your brain and they reach a brain cell over here some of these glucose molecules are going to be able to travel over into the brain cell and that where the brain will have energy okay so so far it’s pretty simple you eat a piece of cake you end up with glucose in your blood and now you have energy so why is this not the

Whole story well imagine that it’s payday and your company gives you your pay for a month of work are you gonna take that money and put it all into your wallet well you probably won’t because you’ll lose it or you’ll be too likely to spend it all at once and so for an analogous reason when you get all this glucose into your blood you’re not just gonna leave it

In your blood you’re going to store it you’re going to put it into storage so that you can use it over a longer period of time so that you won’t just use that glucose quickly over the next hour after you ate that cake so you’re going to put it into storage and here this white cell can be an example of a storage cell and just so you know there is about three

Different places in the body where glucose can be stored one is the liver the liver one is fat fat cells which are also called adipocytes but don’t worry about that it’s liver fat and also it turns out muscle cells you can also store glucose in your muscle cells so to repeat these are cells where you’re going to store glucose so let’s write storage storage so

Let’s keep track of what we’re saying here we’re giving reasons why you want to store your glucose and the first reason we’ve said is so that you can use it over a longer period of time because maybe you won’t have another piece of cake for a while and therefore it would be good if later on when you didn’t have another piece of cake you could just use some of

The stored up so you want to use it over a longer period of time now there’s actually a second reason why you want to get the glucose out of your blood and that is that glucose is toxic so in high quantities and let me tell you cake will give you a lot of glucose in high quantities glucose is actually going to damage your body and that’s why you might want

To get it into these storage cells which can handle it without getting hurt instead of leaving it in circulation where it might damage nerve cells such as this brain cell here but now we’re faced with a conundrum because let’s say now we’re looking at you know your blood maybe a couple hours after you ate the cake and now there’s very little glucose left in

Your blood and you still have your brain cells here that need some glucose to survive and you still have your storage cells here now the point is that at this point when you don’t have too much glucose in your blood you don’t want your storage cells to be taking on glucose you don’t want that so let’s put an x there so the question is how do your storage cells

Know when to take the glucose in and when not to and the answer as you might have guessed is the title of this video which is insulin so insulin is a molecule which is going to tell your storage cells to take up glucose when there’s lots of glucose in the blood and it’s going to not tell your cells your storage cells to take up glucose when there’s low glucose

So you’ll have insulin here let’s try those little triangles a little insulin there so insulin will be present there in the blood insulin so it’s there in the blood and then here we’re not going to have any insulin so how does the insulin know whether to be present in the blood or not well that’s actually an action that’s done by the pancreas the pancreas is

An organ which is somewhere behind the stomach over there something like that and we’re going to draw an orange that’s the pancreas over there let’s point to it so you’re sure you know where it is pancreas and it’s the pancreas job to let out all this insulin when there’s glucose in the blood so let’s just draw for example a one of the cells of the pancreas

This by the way just so you know it’s called the beta cell called the beta cell those are the cells that release insulin so here you have a beta cell from the pancreas and you have your blood vessel coming near it now when the blood vessel has a lot of glucose in it that glucose is going to enter this cell freely and if you notice glucose sometimes enters cells

Freely sometimes it enters cells depending on whether it’s insulin now the beta cells will essentially take it up freely you’ll get lots of glucose in the beta cell and when the beta cell sees that there’s all this glucose in it it’s going to in turn you guessed it secret insulin it’s going to let out some insulin into the blood and then of course on the flip

Side when you don’t have much glucose in the blood for example here let’s let’s just draw two little glucose molecules your beta cell in your pancreas which we’ll draw here beta cell will also not have much glucose because it’ll have used up the glucose from before and it’s not getting any more for the blood vessels so now what do you think well you guessed

It it’s no longer no longer going to be releasing insulin into circulation and so of course as you can tell these two situations happen at the same time and these two situations happen at the same time so to recap what we’ve drawn here is the way that your body knows to push glucose into the storage cells when there’s lots of glucose in the blood and why does

It do that again well to repeat it does it so that you can store the glucose you can save it over time just like you would want to save a check that you received and use it over time rather than keep it in your wallet and blow it all at once and also because the glucose in high quantities is toxic and so these are the reasons for insulin these are the reasons

Why you need insulin and a lot of times people talk about insulin and they never really explain why you need it well here you go here are two good reasons you

Transcribed from video
All about insulin mechanism | USMLE high yield By mad Medico