Lesson video

Hi, I'm Mrs. Hudson, and today I'm going to be teaching you a lesson called Insulin, glucagon and the control of blood sugar level.

This is a biology lesson and it comes under the unit titled Coordination and control: hormones and the human endocrine system.

The outcome of today's lesson is, I can describe the role of the hormones, insulin and glucagon in controlling blood sugar level.

There are five key words that are going to be used frequently across today's lesson, and they are respiration, glucose, glycogen, insulin, and glucagon.

Let's have a look at what those words mean.

Respiration is a chemical reaction in living organisms that releases energy from glucose.

Glucose is a sugar that travels in the blood and is supplied to cells for respiration.

Glycogen is a stored form of glucose found in liver and muscle cells.

Insulin is a hormone secreted by the pancreas when blood glucose is too high, lowering blood glucose levels, and glucagon is a hormone secreted by the pancreas when blood glucose is too low, increasing blood glucose levels.

Today's lesson is going to be split up into two different parts.

In the first part of the lesson, we're going to be looking at homeostasis, glucose and respiration.

And then we're going to move on in the second part to looking at regulating blood glucose with insulin and glucagon.

Let's get going there with the first part of the lesson, homeostasis, glucose and respiration.

Let's look at the definition of homeostasis first.

Homeostasis is the regulation of the internal conditions to maintain optimum conditions for enzyme action and all cell functions.

So our body is constantly regulating the internal conditions to make sure that enzymes are working at their best so that cells can function properly.

And those internal conditions could be the temperature of the body, the amount of water, or what we're talking about today, which is blood glucose concentration.

And for cells to be able to function properly, it relies on enzymes working well.

And if we look here, we've got two different conditions that can affect how well enzymes work.

The first condition is temperature, and you can see that as you increase the temperature, that enzyme activity increases up to a certain point.

So the optimum temperature would be where that dotted line is showing you that is the temperature, at which that enzyme works best, but then after a certain temperature, if it gets too hot, the enzyme will denature and that enzyme will stop functioning.

Another condition that enzyme activity is pH, and depending on which enzyme it is, will depend on what pH the enzyme works best at.

But we can see that again, pH affects the rate at which the enzyme is operating at.

And you can see for this enzyme, the optimum pH is there, but if the pH gets too low or too high, again, the enzyme will denature.

So our body is trying to maintain optimum conditions for enzyme activity so that our cells can function properly.

And this is called homeostasis.

Let's check our understanding of that.

So which is the best definition of homeostasis? A, regulation of the body so that it works efficiently.

B, regulation of internal conditions for optimum cell functioning, or C, keeping conditions inside the body the same.

This is B.

Homeostasis is the regulation of internal conditions for optimum enzyme activity to make sure that there's optimum cell functioning.

Well done if you got that right.

Now we know about homeostasis.

Let's look at glucose in more detail.

Before we begin though, glucose concentration is one of the conditions inside the body that the body is trying to maintain and keep relatively constant.

Glucose is a sugar that travels in the blood plasma and is delivered to most body cells for aerobic respiration.

Aerobic respiration is a chemical reaction that releases energy and is a vital process that keeps organisms alive.

And we can see below we've got the word equation here for respiration.

So the reactants are glucose and oxygen and they react together to produce carbon dioxide and water.

And energy is also released through respiration.

And that is why respiration is so important because energy that then can be released and provided for driving chemical reactions and muscle contraction around the body.

So glucose is a reactant for respiration and it needs to be supplied to all cells.

Glucose is transported through the body in the blood plasma and is delivered to cells where it is used as a reactant for respiration.

Aerobic respiration occurs in the mitochondria.

So you can see here we've got an image on the left-hand side of a blood vessel and the yellow colour is showing the blood plasma, which is the liquid part of the blood that transports lots of substances and one of the substances it transports is glucose, which we can see labelled and the glucose travels through the blood plasma and is delivered to cells.

Now the subcellular structure where aerobic respiration takes place is the mitochondria.

And we can see here we've got one mitochondrion and that the glucose has been delivered to the mitochondrion where aerobic respiration will take place and energy is released.

Even when resting, the body requires energy to drive chemical reactions that keep the body alive.

Glucose is continuously being delivered to cells for respiration.

So even at rest your heart is beating and also chemical reactions are taking place.

And this requires energy which is delivered through respiration.

So here we've got somebody who is resting, they're at sleeping, the body is at rest, and there's still chemical reactions taking place in the body.

The heart is still beating, which is a muscle that requires energy, so therefore glucose is being transported through the blood plasma to the mitochondria, and that glucose then is being used in aerobic respiration to release energy to drive those chemical reactions.

Conditions inside the body change frequently, for example, due to eating, fasting and exercise.

There are other things as well that will change the conditions.

They're just a few examples that we're going to talk about.

So during exercise and fasting, blood glucose levels will decrease.

So here we can see some athletes who are exercising and then you've got a picture of a lunch with a cross on showing you that nothing has been eaten, so fasting, and exercising and fasting cause blood glucose to decrease.

After eating or drinking substances that contain sugar or carbohydrates, blood sugar levels will increase.

So we can see here a picture of some packed lunches and they've got bits of fruit in which contains sugar, but also food which will have carbohydrate in which gets broken down into sugar.

So after you digest that food, your blood glucose will increase.

So exercise and fasting decrease blood glucose levels and eating increase glucose levels.

Exercising causes blood glucose levels to decrease because our body has to increase the rate of respiration in order to supply muscles with more energy for contraction.

If respiration rate increases, more glucose will be delivered to cells decreasing blood glucose levels.

So we can see here the same picture of the athletes and as these athletes are exercising, their muscles are going to be contracting and for the muscles to contract, they need to be supplied with energy and that energy is supplied through respiration.

And respiration requires glucose.

So when those athletes are exercising, there's going to be more glucose being used up in respiration.

So that will mean that blood glucose levels decrease.

Naturally, throughout the day, blood glucose levels rise and fall and the body has to constantly monitor the levels of blood glucose and will secrete hormones to return levels back to normal.

And here we can see a little infographic which is showing you the natural variations of blood glucose throughout the day.

And between those two lines, that is the ideal range of blood glucose levels and the body's constantly regulating blood glucose levels and then will secrete different hormones depending on whether blood glucose increases or decreases to keep levels within that ideal range.

So here we can see that blood glucose is increasing after eating breakfast and then blood glucose will decrease after not eating for a period of time.

And then again you eat lunch which causes the blood glucose to increase and then it will decrease again, and then we can see it goes back up.

So potentially somebody's eaten dinner and they've gone back up again.

And then also after they've eaten dinner, exercising might cause the blood glucose to decrease again.

So naturally throughout the day, blood glucose rises and falls and the body monitors those levels and secretes hormones to keep them within the ideal range.

It's important for the body to regulate the concentration of glucose within our blood and keep it within very narrow limits.

And this is because there are quite drastic symptoms of low blood glucose.

So initially you will start to experience sweating, pallor, so you might look quite pale, you become irritable, you are hungry, you may have a lack of coordination and loose balance and you can become quite sleepy and tired.

Now, high blood glucose, if it remains high over a long period of time, you may experience these symptoms. So a dry mouth, thirst, weakness, headache, your vision could become blurry and you may frequently need to urinate.

Now if blood glucose levels fall too low, a person could fall into a coma and this can be fatal, so it could cause death if untreated.

If blood glucose remains high over a long period of time, it can cause organs to stop functioning, which can also become fatal.

Let's check our understanding of that.

Glucose is the reactant for which chemical reaction? A, photosynthesis, B, respiration, or C, diffusion.

This is B, respiration.

Glucose is a product of photosynthesis, and diffusion is not a chemical reaction.

It's a process that moves particles from high concentration to low concentration.

Well done if you've got that right.

Next question is true or false.

At rest, the body does not need to supply cells of glucose.

True or false, and then justify your answer.

A, at rest cells do not respire as the body is not active.

And B, at rest cells respire to release energy to drive chemical reactions.

So this is false.

At rest cells do need to be supplied with glucose and the justification is B.

At rest, cells respire to release energy to drive chemical reactions.

So well done if you got that right.

We're ready now to do the first task of the lesson task A.

In the first part of task A, you need to annotate the diagram to show why it is important for glucose to be delivered to cells of the body.

And there's a diagram there, it's got some labels on, so you need to write the labels on and maybe explain in more detail why it's important for glucose to be supplied to cells.

And then in the second part, you're going to annotate this diagram to show what might cause the changes in blood glucose levels.

Then part three are these statements about glucose levels and respiration correct or incorrect? A, it is not dangerous for blood glucose levels to become too high or too low.

B, glucose is constantly being delivered to cells for respiration and C, during exercise, blood glucose levels increase as respiration rate decreases.

So are those correct or incorrect? And then for part four, you're going to use the statements you identified as being incorrect in part three and write out the correct statement.

I'm sure you're going to do a fabulous job.

Make sure your answers are as detailed as possible, pause the video and then press play when you are ready for me to go through the answers.

Let's see how we did.

So annotating this diagram, you've got glucose travels in the blood plasma and is delivered to cells and then the yellow part is the blood plasma.

Then you've got the mitochondrion and aerobic respiration occurs in the mitochondria inside cells, releasing energy to drive chemical reactions and muscle contraction.

And then at the end, energy is released.

You might have written that in a slightly different way, so pause the video and add in any extra detail you might need to your answers.

But for question two, we were annotating this graph.

So blood glucose is increasing after eating breakfast and then blood glucose is decreasing after not eating for a period of time.

Then eating lunch causes blood glucose to increase and then finally, exercising after dinner causes blood glucose to decrease.

Then for number three, statement A is incorrect.

It is dangerous for blood glucose levels to become too high or too low, and then B is correct and then C is incorrect.

So let's have a look now at correcting those incorrect statements.

So for the first one, it is very dangerous for blood glucose levels to become too high or too low.

If blood glucose concentration decreases too much, you could fall into a coma and it can become fatal.

If blood glucose concentration is increased for a long period of time, it can cause organs to stop functioning, which can also be fatal.

And then the second statement, during exercise, blood glucose levels decrease as the respiration rate increases and the respiration rate increases as muscles need energy to contract.

And this energy is transferred through respiration.

So well done if you managed to correct those statements.

Really great job.

If you need to pause the video to add any extra detail into your answers, please do, but we are going to move on to the second part of the lesson now.

Great job with the first part of the lesson.

So we know what homeostasis is and we know what glucose is used for and that is respiration.

Let's move on now to looking at regulating blood glucose with insulin and glucagon.

Can you remember which gland in the endocrine system this is? So what gland is that line pointing towards? That is the pancreas.

And the pancreas is the organ in the body that detects changes in blood glucose concentration.

So the pancreas we've spoken about before as being a gland, but it is also an organ in the body that has other functions as well.

The reason why it's a gland is because it's secretes hormones, which we're going to talk about, but the pancreas is the organ that detects changes in blood glucose concentration.

If blood glucose concentration is too high, the pancreas will detect this change and secrete a hormone called insulin.

So here, if the blood glucose is too high, the pancreas detects that change and secretes the hormone insulin.

Insulin travels in the blood plasma to its target cells in the liver and in the muscle.

So here we've got the pancreas again, it detects an increase in blood glucose concentration, it secretes the hormone insulin and that insulin hormone travels in the blood plasma to the target cells which are in the liver and the muscles.

Insulin acts on the liver to reduce blood glucose concentration by, increasing the amount of glucose absorbed from the blood into the cells in the liver, and then converting excess glucose into glycogen which is stored in the liver and muscle cells.

So if this was the liver here, when insulin reaches the liver, it causes the liver, first of all, to absorb glucose from the blood into the liver, and then it takes that glucose in the blood and it converts it into glycogen, which is stored in the liver and muscle cells.

And both of these things decrease the amount of glucose that is in the blood.

So let's check our understanding of that.

Which organ is responsible for detecting changes in blood glucose concentration? A, liver, B, pancreas or C, stomach? This is B, the pancreas.

The liver is the target organ that the insulin acts on, and the stomach is an organ where food is churned up.

So again, the pancreas is the organ in the body that detects changes in blood glucose concentration, we've already mentioned that, but at this time, if blood glucose concentration is too low, the pancreas will detect this change and secrete a hormone called glucagon.

So I always try and remember this in the way that if glucose is low, if glucose is gone, then you secrete glucagon.

So if blood glucose is low, the pancreas detects this change and secretes the hormone glucagon.

Glucagon travels in the blood plasma to its target cells in the liver and in muscle.

So again, the pancreas detects these low glucose levels and its secretes the hormone glucagon that travels in the blood plasma and it targets cells in the liver and the muscles.

Glucagon acts on the liver to increase blood glucose concentration by, stopping glucose being absorbed from the blood by cells, and then converting glycogen which is stored in the liver and muscle cells into glucose and releasing it into the bloodstream.

So this is the opposite effect of insulin.

We are trying to increase the blood glucose levels here.

So if this was the liver, if the blood glucose levels are too low, then the liver will stop absorbing glucose from the blood.

And what it will do is convert glycogen that's stored in the liver and muscle cells and it will convert it into glucose into the blood.

And both of these things will increase the amount of glucose that is in the blood.

The pancreas helps to regulate blood glucose levels by detecting changes in blood glucose concentration and then secreting insulin and glucagon to bring levels back to normal.

So here we can see the natural variations that we have throughout the day of glucose concentration, and those two lines are the ideal range to keep the levels between.

So when the levels start to increase, so blood glucose is increasing, insulin is secreted, causing blood glucose to return back to normal, and we can see it goes up a certain amount.

And then the body says right, the blood glucose is too high, it secretes insulin which brings the blood glucose back to normal, but then at times, the blood glucose will decrease and this time the pancreas detects it and it secretes glucagon which causes blood glucose to increase back to normal.

And this is the body's way of maintaining blood glucose concentration.

This table summarises the similarities and differences between the regulation of blood glucose concentration with insulin and glucagon.

So we can see at the top of the table we've got blood glucose concentration, the organ that detects the change, the hormone's secreted, the target, and then the effect that is brought about.

So we're going to look at if blood glucose concentration is too high to begin with.

So the organ that detects the change is the pancreas, the hormone secreted is insulin and the target cells are the liver and the muscle cells.

And the effect that is brought about by insulin is that glucose in the blood is converted into glycogen in the liver.

And then if blood glucose concentration is too low, the organ that detects the change, again, that's the pancreas, but this time the hormone that's secreted is glucagon.

The target cells are the same, it's the cells in the liver and in the muscle.

And the effect this time is that glycogen, which is stored in the liver, is converted into glucose in the blood.

And if we look at the this again in kind of a whole picture view, the organ that detects changes in blood glucose levels is the pancreas.

So if blood glucose level becomes too high, the pancreas detects that change, it then secretes the hormone insulin which travels to the liver and muscle cells where glucose is converted into glycogen, and then normal blood glucose levels will be restored because it will decrease the amount of glucose in the blood.

Again, if we've got low blood glucose, the pancreas detects that change, but this time it secretes glucagon, which travels to the liver and muscle cells and glycogen in the liver and muscle cells is converted into glucose and released into the blood, which will increase blood glucose levels back to the normal level.

Let's check our understanding of that.

So name the hormone that is secreted by the pancreas when blood glucose concentration is too low.

A, insulin, B, glycogen, or C, glucagon.

This is C, glucagon.

So when glucose is low or glucose is gone, you secrete glucagon.

Insulin is secreted when blood glucose is too high and glycogen is the store of glucose in the liver and muscle cells.

True or false question now.

Insulin causes blood glucose concentration to decrease.

True or false and then justify your answer.

A, insulin causes glucose in the blood to be converted into glycogen and stored in the liver, or B, insulin converts glycogen in the liver into glucose in the blood.

So this is true and the justification is A.

Insulin causes glucose in the blood to be converted into glycogen and stored in the liver, which decreases blood glucose concentration.

Fantastic job if you got that right.

We're ready now to move on to the second task of our lesson, task B.

And in the first part you need to fill in the missing labels on this diagram to show how the pancreas regulates blood glucose concentration.

So it's similar to the diagram we did before.

And then question two, the graph shows how Jun's blood glucose concentration changes throughout the day.

A, explain how blood glucose changes between point A and point B, and then B, explain how blood glucose changes between point C and point D.

I'm sure you're going to do a fantastic job.

Pause the video and give as much detail in your answers as you can and then press play when you are ready for me to go through.

So let's see how we did.

So part one, filling in the details of this diagram.

So the pancreas secretes insulin if you've got high blood glucose and then glucose is converted into glycogen in the liver and muscle cells and normal blood glucose levels are restored.

On the opposite side, if you've got low blood glucose, glucagon is secreted and then glycogen in the liver and muscle cells is converted into glucose and released into the blood.

But well done if you managed to get those right.

For the second part, looking at Jun's blood glucose concentration changing.

So explain how blood glucose changes between point A and point B.

So you're going from a high blood glucose and it's decreasing down.

So at point A blood glucose is increasing.

The pancreas detect this and secretes insulin.

Insulin travels in the blood to the liver and muscle cells.

Insulin causes the cells to absorb more glucose and convert glucose to glycogen that is stored in the liver.

And then this decreases blood glucose levels back to their normal level, which is around point B.

Now looking at the second part, so explain what is happening between point C and D.

This time we've got an increase in blood glucose level.

So at point C, blood glucose is decreasing.

The pancreas detects this and secretes glucagon into the blood, glucagon travels to the liver and muscle cells where it stops cells absorbing glucose and converts stored glycogen into glucose, releasing it into the blood.

The blood glucose levels then increase back to normal levels, which is D.

Fantastic job if you managed to get those right.

If you want to pause the video to go back and check anything and add any extra detail into your answers, then please do.

I'm going to summarise everything that we've learned in the next slide.

So today's lesson has been about insulin, glucagon, and the control of blood sugar levels.

And we started off our lesson by talking about homeostasis and how that is the regulation of internal conditions for optimum enzyme activity and cell functioning.

And then we talked about glucose and we said that glucose is a reactant for respiration and the body needs to carefully regulate the concentration of glucose in the blood.

If blood glucose levels are too high, the pancreas secretes insulin, which targets the liver and muscle cells converting glucose into glycogen, which is stored in the liver.

And then we said that blood glucose level concentration will decrease back to normal.

And then we talked about if blood glucose levels are too low, the pancreas secretes glucagon, which targets the liver and muscle cells and then stored glycogen is converted into glucose and released into the blood.

Blood glucose concentration will increase back to normal.

So our body is constantly regulating the amount of glucose and then either secreting insulin or glucagon to make sure that those levels are held within the ideal range.

I really enjoyed today's lesson.

I hope you have too, and I look forward to seeing you next time.