This lesson is called, The Importance of Maintaining Constant Conditions in the Body, and is from the unit, Coordination and Control: Maintaining a Constant Internal Environment.

Hi there, my name's Mrs. McCready and I'm here to guide you through today's lesson.

So thank you very much for joining me today.

In our lesson today, we're going to explain why it is important for humans to maintain constant conditions inside the body.

We're gonna have a look at a number of examples to help explain that.

Now in our lesson today, we're gonna come across a good number of keywords and they're listed up here on the screen for you now.

You may wish to pause the video to make a note of them, but I will introduce them to you as we come across them.

So firstly, we're gonna have a look at some of the problems caused by changing internal conditions and see why it's important that we keep those internal conditions constant as much as is possible.

And then, we're gonna move on and have a look at how the body maintains some of those constant conditions.

So are you ready to go? I certainly am, let's get started.

So we can see just by looking at our body how complex it is and how many different aspects of our body there are.

Just by looking at the outside of our body, we can see that there are plenty of different specialised cells, each with their own characteristics that allow our body to function properly.

And if we look in a bit deeper, then we can see that there's even more specialised cells inside.

Now, that complex combination of all these different specialised cells relies upon an also complex combination of different chemical processes within those specialised cells, tissues, and organs.

And all of that has to work together for us to survive and thrive.

So every part of our body has a specific chemical and structural process and role, and each of those has a distinct role to play within our body.

And all of those parts of our body must work together effectively in order to keep us alive and healthy.

Now, enzymes form an essential part of every cell, for if it weren't for enzymes, then the vast majority of cellular processes simply wouldn't happen because enzymes catalyse, that means speed up, the rate of chemical reactions.

And if it weren't for enzymes speeding up the rate of reactions, then those reactions wouldn't happen within our body.

So enzymes are fundamental.

They take a substrate into their active site, they process that by either breaking bonds or making bonds, and then release the products out.

But in order to function effectively, the active site must be a specific shape.

Now, enzymes work fastest at optimum conditions.

That means an optimum temperature and also an optimum pH.

And if we move away from those optimum conditions, the rate of reaction will slow down and it may well come to a halt if the move away from the optimum is great enough.

So at lower temperatures, the enzymes will just collide less often with the substrates they are catalysing and therefore chemical reaction rate will slow down because those reactions are happening less frequently.

And at higher temperatures, or in different pHs, the active site changes shape and that reduces the ability for the enzyme to catalyse the reaction.

So maintaining optimum conditions is really important fundamentally because if we don't maintain optimum conditions, then enzymes will reduce in their ability to catalyse reactions and that will reduce our ability for our cells to carry out the jobs that they need to do in order to keep us healthy and alive.

Now, changes in temperature, internal body temperature, are noticeable.

And it doesn't take much of a change away from our core temperature of 37 degrees for us to notice that we're not working well and for us to start feeling ill.

So if our temperature increases above 37 degrees, then we start to feel ill with a fever.

And a fever is a sign that we have an infection and we're not very well.

Now, if those temperatures increase and are sustained above 40 degrees centigrade, then the enzymes don't just slow down, but they can start to denature as well and that can be very, very risky indeed.

However, that high fever doesn't just come about because of a coincidence.

It is coordinated by our body because by increasing our body temperature, yes, we reduce the ability for some of our enzymes to work effectively, but more importantly, it denatures enzymes in the pathogens that are causing us the disease in the first place.

And by doing so, this reduces the ability for those pathogens to cause us harm because it inhibits their ability to reproduce.

So us running a fever feels awful and is somewhat damaging to us, but it is more damaging to the invading pathogen and actually helps us to recover.

So next time you're running a fever, I hope you give your body a bit of a thank you for dealing with the pathogen effectively.

So let's quickly check our understanding.

Which of the following statements explain why enzymes stop working at extremely high body temperatures? Is it A, the rate will decrease because the enzyme's active site has changed shape? Is it B, the rate will decrease because there will be a better fit between enzyme and substrate? Or is it C, the rate will decrease because there are more successful collisions? I'll give you five seconds to think about it and spot any mistakes if you can in any of the incorrect statements.

So did you notice that statement A is correct? Well done, but what about B? So B is incorrect because instead of there being a better fit, there will be a worse fit.

And statement C is incorrect because there will be fewer successful collisions, not more.

Did you spot the mistakes as well as getting the correct answer right? Well done if you did.

Now, if a significant increase in body temperature is sustained, it can lead to a condition called hyperthermia.

Hyper means over, thermia means heat.

So hyperthermia is where we are too hot, but not just a little bit warm, properly too hot, a significant and sustained increase in body temperature over 37 degrees.

Now people who are exposed to sustained high temperatures without sufficient water or shade risk developing hyperthermia because the body really struggles then to lose enough heat to maintain its optimal internal temperature.

And if this is left untreated, it can lead to death.

Conversely, if there is a significant reduction in body temperature and that is sustained, it can lead to a condition called hypothermia where hypo means under and thermia means heat.

So this is a sustained reduction in internal body temperature.

Now, people who get trapped on mountainsides or stranded in cold water risk developing hypothermia because the body struggles to maintain its internal optimum temperature because the cold external environment is cooling the body down too much.

And if that is left untreated, it can lead to death.

So we can see how hyperthermia and hypothermia are both critical conditions.

So let's just check our understanding.

Maintaining an optimum internal temperature is important in keeping us alive and healthy, true or false? So you should have said that that is true, but why? So you should have said that maintaining an optimum internal temperature is important because temperatures below the optimum can slow enzyme activity down and temperatures above the optimum can change the shape of an enzyme's active site.

Did you get a good explanation to that statement? Well done if you managed that.

Now, we've looked at temperature, but what about water? Because water is also critical to life.

Now the term water balance describes the concentration of water and mineral ions within our blood.

Now, the brain monitors water balance and can adjust the amount of water and ions we retain and lose depending on how the blood compares to cellular levels.

So the brain is constantly monitoring how much water we have in our blood and therefore if we need more or have too much.

Now we can lose water through a number of different ways.

Urination is the most significant way of losing water when we go to toilet, but we can also lose water by sweating via our skin and we can also lose water from our lungs when we exhale.

Now we cannot control the amount of water that we lose by exhalation from our lungs.

That just happens.

It's not needed or wanted, really.

It's just one of those things that occurs.

But the brain controls the amount of water that we can lose through urination and through sweating.

Now, if we lose more water than we take in, this can lead to a condition called dehydration.

And dehydration means that there is insufficient water in our cells for chemical reactions to take place efficiently.

Now, mild dehydration is relatively easy to manage because it'll make us feel a little bit thirsty and we respond to that by having a drink.

But if we lose 15% or more of body water, it can lead to death.

So you can see how losing water can become really quite a critical condition.

So we've seen how maintaining constant internal temperatures and water levels is really important and maintaining a constant optimal internal environment in response to internal and external changes is called homeostasis.

So homeostasis is about maintaining a constant internal environment.

Homeostasis is essential for maintaining our health and keeping us alive.

If our temperature increases or decreases significantly from the optimum, or if our water levels particularly decrease away from the optimum, then those conditions, hyperthermia, hypothermia, and dehydration, can lead to death if left untreated.

So homeostasis, this process of maintaining a constant internal environment, is a critical role of the brain and the body.

So let's check our understanding on this.

Can you complete the gaps in the sentences? Something is important for maintaining a constant something environment.

Losing too much water can lead to something and ultimately cause something if left untreated.

I'll give you five seconds to think about it.

Okay, let's check our answers.

So homeostasis is important for maintaining a constant internal environment.

Losing too much water can lead to dehydration and ultimately cause death if left untreated.

Did you get those four words correct? Well done if you did.

So what I'd like you to do now is to consolidate our understanding by firstly defining the term homeostasis.

Then I'd like you to explain why changes away from the optimum may be so dangerous to our health.

And I'd like you to reference examples of enzyme function, body temperature, and water levels to illustrate that.

Then finally, consider this, that people over the age of 50 may have a decreasing sense of thirst.

So can you use that to explain why intense heat in summer may be particularly dangerous for those aged over 50? So pause the video and come back to me when you're ready.

Okay, let's check our work then.

So first of all, I asked you to define the term homeostasis.

So you should have said that homeostasis is the regulation of the internal conditions to maintain optimum conditions for enzyme action and all cell functions.

You may well have phrased that differently but have talked about maintaining internal conditions as part of that.

Then I asked you to explain why changes away from the optimum may be so dangerous to our health.

So you might have included that enzymes work fastest in optimal conditions such as at a specific temperature and pH, and that outside these conditions, the rate of enzyme activity slows and can stop completely.

Now enzymes are essential for catalysing most cellular reactions, and hyperthermia and hypothermia are examples of how changes away from the optimum temperature can damage our health.

Now water is required for chemical reactions to take place efficiently, and dehydration is caused when water levels in the body reduce and can be fatal.

So did you include those salient points? Add anything that you might have missed, and well done indeed.

Then I asked you to consider this, that people over the age of 50 may have a decreasing sense of thirst and why therefore is intense heat in summer particularly dangerous for those aged over 50? So you might have written that intense heat makes it difficult for the body to cool down effectively, and sweating increases, which means more water is lost from the body than normal.

Now, elderly people have a reduced sense of thirst, so may not drink enough water to keep themselves hydrated.

And in intense heat, this can lead to significant dehydration, which if left untreated can lead to death.

And this is why intense heat in the summer may be particularly dangerous for those over the age of 50.

Did you make all of those notes? Well done if you did.

Okay, let's move on to see how our body maintains those constant conditions.

So homeostasis is about the maintenance of internal body conditions and this is controlled through the nervous and endocrine, that's the hormone responses, and is overseen by the brain.

So these control systems require three main components: receptors, which detect changes in the environment; a coordination centre, such as the brain or the spinal cord or the pancreas that receives the information and processes it from the receptors; and then effectors, which are muscles or glands that bring about responses that restore the optimum levels.

Now let's quickly check our understanding.

What I'd like you to do is match the name of the part of the control system with the example, and I'll give you five seconds to think about it.

Okay, so you should have matched the receptor to the temperature sensor, the coordination sensor to the brain, and the effector to the sweat gland.

Well done if you got those correct.

So homeostasis, this process of maintaining optimum internal conditions, requires processes that work against each other in order to return to optimum conditions.

So if the temperature increases, there needs to be a response that brings that temperature down, or if the temperature reduces, there needs to be a response that brings it up.

So effectors that work against each other are antagonistic, they are working against each other.

That's what that word antagonistic means.

So consider a situation when you have become too hot.

How did your body cool you down? What about when you became too cold? How did your body warm you up? Have a think about that for a moment.

So thinking about a time when you got too hot, you should have noticed, you should have remembered that you sweated more.

So the sweat glands in your skin produced sweat, and the process of evaporating that sweat away from your skin cooled you down.

What about when you got too cold? Well, you should remember that when you got too cold, you shivered.

And by shivering, that generated heat because our muscles were contracting and relaxing quickly.

That generated heat to warm us up.

Now these two effects are antagonistic.

Sweating and shivering are antagonistic effects.

Now, we can model how antagonistic effects work by simulating this in the lab.

So let's say we're trying to keep a beaker of water at a constant temperature, maybe 40 degrees.

If the water temperature moves away from the optimum, how would we heat that water up or cool it down? Just have a think about that for the moment.

So how would we heat the water up if it started to cool? Well, you probably considered a Bunsen burner to heat the water up.

But what about cooling the water down? Well, perhaps you considered adding ice cubes to cool it down.

So in this scenario, the Bunsen burner and the ice cubes are antagonistic effectors.

They are causing antagonistic effects because they are working against each other.

So let's consider that then.

Which of these is an example of a pair of antagonistic effects? Is it A, insulin which decreases blood sugar and glucagon, which increases blood sugar? Is it B, factor VIII, which clots blood, and fibrinogen, which seals cuts to stop bleeding? Or is it C, sweating to cool the body down and shivering to warm the body up? I'll give you five seconds to think about it.

Okay, so the examples which are a pair of antagonistic effects include insulin and glucagon.

One decreases blood sugar and the other increases blood sugar, and sweating and shivering because sweating cools the body down and shivering warms the body up.

So these are examples of antagonistic effects.

Well done if you spotted both of them.

So what I'd like you to do now is to consolidate our understanding by defining the term antagonistic with an example of effectors and effects.

Then I would like you to explain with an example how antagonistic effectors maintain homeostasis.

You may wish to use the control of body temperature as an example, but you could choose an alternative example if you prefer.

So pause the video and come back to me when you're ready.

Okay, let's see how you got on then.

Firstly, I asked you to define the term antagonistic with an example of effectors and defects.

So you should have said that antagonistic effectors and effects work against each other.

For example, effectors include sweat glands and muscles and effects include sweating and shivering to control body temperature.

You might have given other examples.

That's absolutely fine, as long as they are antagonistic effectors and effects.

Then I asked you to explain with an example how antagonistic effectors maintain homeostasis.

So you may have written that homeostasis is about maintaining a constant internal environment and that antagonistic effectors work against each other in order to do this.

Now, when our body temperature increases, sweat glands produce sweat and evaporating sweat takes heat away and reduces our body temperature back to normal.

When our body temperature decreases, our muscles shiver, and when we shiver, our muscles contract and relax quickly, which generates heat and this increases our body temperature back to normal.

So you may well have used an alternative example.

That, again, is also fine, but do just check over your answer and make sure that you've given a correct example of antagonistic effectors and the effects that they are having.

Well done indeed.

So we've come to the end of lesson today and today we've seen that our body is maintained as a constant optimum internal state known as homeostasis.

And changes away from this point are quickly adjusted using pairs of antagonistic effectors and the effects that they create.

And this ensures that conditions such as body temperature and water balance are maintained at optimum levels.

And by doing so, this preserves optimum conditions for enzyme activity and ensures we stay healthy.

Because if changes away from the optimum conditions are sustained, it can cause conditions such as hyperthermia where we're too hot, hypothermia where we're too cold, or dehydration, where there is too little water in our body, and all of these, if left untreated, can lead to death.

So I hope you found our lesson interesting today and I hope to see you again soon, bye.