Lesson video

This lesson is the role of the skin in thermoregulation 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 describe the roles of various parts of the skin in controlling human body temperature.

Now we're going to come across a good number of keywords in our lesson today, 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.

Now in our lesson today, we're going to first of all look at body temperature and skin anatomy before we consider how our body responds to decreases in body temperature and increases in body temperature.

So I hope you're ready to get started.

I certainly am.

Let's go.

So the human body maintains an internal body temperature within a very small range of 37 degrees centigrade, plus or minus half a degree.

It really is a very, very small window.

And this is because cells, enzymes, and cellular processes work most efficiently within this narrow temperature.

So you can see on the graph of the rate of enzyme reactions that there is an optimum temperature.

And beyond this, in either direction, outside of that optimum temperature, the rate of the enzyme reaction decreases.

And that is true of all cellular processes as well, which is why human body temperature is maintained within this very specific temperature range.

Now, changes to the external environment can cause our internal body temperature to change.

So if you think about how you felt on a really warm day or a very cold day, you'll see how the external temperature influences how your internal temperature responds.

So intense sunlight, a warm breeze, putting yourself in cold water, a small part of you or all of you, if you've ever been in one of those ice baths, all of these factors can cause our internal body temperature to change either up or down.

Now the skin can sense changes in temperature and enable the body to respond appropriately to these changes.

So you can see there in the diagram, there is a temperature receptor embedded within the skin.

And the temperature receptor is monitoring the external temperature outside of our body.

Now the skin is made up of various different parts.

So let's have a look at the anatomy of the skin.

Well, the bit that we're most familiar with is the epidermis, the top layer of skin cells.

And these include bits of skin which slough off as time passes and the fresh skin underneath that as well.

Below that layer are the middle layers of skin called the dermis.

And underneath that is a layer of fatty tissue which helps to provide us with some insulation and some protection to keep us warm and to protect the inside body parts as well.

Also, within the skin, which is actually really complicated, there are hairs.

Now we know that.

We can see them on the surface of our skin, protruding through the epidermis of the skin.

And the hairs are connected to muscles called erector pili muscles.

Also, within the lower parts of the skin, so within the dermis layer of the skin, is the temperature receptor, also sweat glands, and also, and perhaps slightly lower than that as well, within the fatty tissue, venules, which are small veins, and arterioles, which are small arteries.

So there's lots of different parts that make up the skin.

So which label shows the erector pili muscle? Is it a, b, c, d, e, f, or g? I'll give you five seconds to think about it.

So you should have identified that the erector pili muscle is label C.

Well done.

What about the sweat gland? Which label shows that? So you should have identified the sweat gland as Part D.

Again, well done.

And which part shows the arteriole? So you should have identified part G as the arteriole.

Well done.

So what I'd like you to do now is to firstly give two examples of external factors that can cause the human internal body temperature to change.

And then I'd like you to add labels to the diagram of the skin and label all the different parts that we've had a look at.

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

Okay, so external factors might have included intense sunlight, immersion in cold water, a warm breeze, a cold shower, all sorts of things like that.

You might have had many examples, more than possibly two, and a whole variety of things.

But they have to be external factors, not things that are happening inside our body, like a fever for instance.

Then I asked you to label the diagram of the skin and the skin anatomy.

So you should have labelled the erector pili muscle, the temperature receptor, the venule, and the arteriole, the hair, the epidermis, which is the top layer, the dermis, which is that middle layer, the sweat gland, and the fatty tissue.

So your labels might be in different locations from mine, but make sure they're pointing to the correct parts of the skin.

And again, well done.

Okay, so let's have a look and see how our body responds to decreases in body temperature.

So if our body temperature decreases by a significant amount for a long period of time, it can cause our cellular processes to slow down.

And this, if left unchecked, can lead to death.

Now our body responds to decreases in internal temperature by a number of different processes, and one of those processes is shivering.

And I'm sure you're familiar with that.

So this is where our muscles contract and relax repeatedly and very, very rapidly.

And the reason we shiver is because it generates heat through cellular respiration.

Cellular respiration is an exothermic process.

That means it gives out heat.

That means it warms us up.

And so shivering is a way of us warming our body up.

But in addition to this, our skin can also respond to temperature changes in our body.

So the responses of our skin to a decrease in temperature includes the erector pili muscles contracting, the hair standing upright, and the constriction of the arterioles.

But why do these responses occur? So the erector pili muscle contracts, and what that does is cause the hairs to stand upright.

The hairs stand upright because the erector pili muscles contract.

And the hair standing upright is useful because it traps an insulating layer of air against our skin.

And because air is an insulator, it means that less heat is lost from the skin, and therefore that heat is kept within our body.

Now, obviously, if you've got a very fine layer of hair on your skin, it's not going to have a great impact.

And you'll see animals who live in cold conditions with a very, very dense fur because of this precise reason.

But nevertheless, it will have an impact and keep some heat inside our body.

The arterioles vasoconstrict.

So the muscles in the arteriole wall contract, and that reduces the amount of blood that is going to the surface of the skin.

And this is a really useful feature because what it does is reduce the amount of heat available at the surface of the skin that can be radiated away from the body.

In other words, it keeps the heat within the central core of our body.

And if you've been out in snow or icy conditions for a really long time, you'll find that your fingers go quite pale.

And this is because the blood is being drawn away from the skin and kept within the central part of the body, because this reduces the amount of heat that we can lose through radiation.

So that helps to conserve heat inside the central part of our body and stop it from being lost to the external environment.

So which of these responses occur in our skin when our body temperature decreases? Is it a, erector pili muscles contract and hairs stand upright? Is it b, shivering? Or is it c, vasoconstriction of blood vessels? I'll give you five seconds to think about it.

So you should have said that the responses that occur in our skin include a and c.

Now all of these responses occur when our body temperature decreases, but only erector pili muscle contraction and vasoconstriction occur within our skin.

So I'd like you to check and understand that work by firstly completing the table to show how the body responds to decreases in temperature.

And then I would like you to consider this scenario, that what happens if you hold an ice cube onto the skin of your arm? What will happen to your skin? And can you explain why? You don't have to do that, but I'd like you to have a think about what will happen anyway.

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

Okay, let's check what you've written.

So firstly, I asked you to complete the table to show what's happening when the body temperature decreases.

So to blood flow, you should have written that vasoconstriction causes decreased blood flow to the skin surface, which reduces heat loss by radiation.

For the body hair, you should have said that the erector pili muscles contract, which causes the hair to stand upright, which traps a layer of air which provides insulation and reduces heat transfer, or you might have said reduces radiation.

And in other changes, you should have said that muscles contract and relax repeatedly, causing shivering, which increases body temperature through heat released through exothermic cellular respiration.

So just check over your work and make sure that you've got all of those parts.

Then I asked you to (indistinct) what would happen to your skin if you held an ice cube on the skin of your arm, and why? So you might have written that your arm would become pale because vasoconstriction of blood vessels will draw blood away from the surface of the skin to conserve heat, that your arm hair might stand upright because the erector pili muscles will contract, and you might also shiver to generate heat.

Now if you tried that, excellent job.

And hopefully you saw all of those responses.

Perhaps not shivering, actually, but certainly your skin becoming paler and your hair on your arms standing upright as well.

Okay, well done.

Okay, so let's have a look at the opposite scenario, when our body temperature increases and how our body responds to that.

Now, just as with sustained decreases in temperature, so sustained increases in body temperature will also cause cellular processes to slow down.

And there are a good number of behavioural responses that we adopt to increasing body temperatures, such as fanning ourselves, spreading ourselves wide and outright so that we increase our surface area, having cold drinks and ice cream, things like that.

And all of these responses help to increase the speed at which heat is lost from the body, which helps us to cool down faster.

But our skin also responds to changes in body temperature.

And let's have a look at this in a bit more detail.

So the responses to the skin to increases in temperature include the erector pili muscles relaxing, hairs lying flat, the arterioles vasodilating, and sweat glands secreting sweat.

But again, why do these responses occur? So the erector pili muscles relax.

Now you can probably guess why based on what we've already covered.

But the erector pili muscles relaxing causes the hairs to lie flat, because those erector pili muscles are connected to the base of the hair.

Now the hair lying flat means that they cannot trap a layer of insulating air, and therefore heat can radiate away from our skin much faster as a result.

So we can lose that extra heat much more quickly.

Now the arteriole vasodilate.

And again, you can probably have a good idea about why this is based on what happens when we are cold.

So vasodilation increases blood flow to the surface of the skin.

And what this means is that more heat is at the surface of the skin, which means that more radiation of heat can occur.

So we can lose heat faster because heat is being brought to the surface out of our skin.

We can see that because we'll flush pink when we're really hot, and our skin will feel really warm as well because that internal heat is being taken to the surface of the skin so that it can radiate away really quickly.

Now we've also said that sweat glands secrete sweat.

And sweat is a really useful way of removing heat from the body because when it evaporates, it takes heat with it.

It requires heat in order to turn the liquid sweat into gaseous sweat and allow it to move away from the skin.

And that process of heating it up so that it evaporates requires heat, which is being provided by our internal body.

And therefore we can radiate heat much faster because the evaporation of sweat is taking heat away from our body and using it in order to evaporate.

So let's check ourselves on that.

What I'd like you to do is to complete the sentences to describe the response to the increased body temperature.

So blood vessels something to bring more blood to the skin surface.

Erector pili muscles something so body hair something.

And something increases heat loss via evaporation.

So I'll give you five seconds to think about all of those blanks.

Okay, let's check our work.

So blood vessels vasodilate to bring more blood to the skin surface.

Erector pili muscles relax so body hair lies flat.

And sweating increases heat loss via evaporation.

Did you get all of those correct? Well done if you did.

So what I'd like you to do now is to firstly complete the table to show how the body responds to increases in temperature.

Then consider this scenario, that you've put an activated heat pack on your skin.

What do you think will happen to your skin in response to that heat, and can you explain why? And then consider this final scenario, that a person has been running a marathon on a warm day.

So what do you think might happen to the thermoregulatory responses if they don't drink enough water during the race? And the thermoregulatory responses are just the way the body responds to temperature changes.

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

Okay, let's check our work then.

So firstly, I asked you to complete the table to show how the body responds to increases in temperature.

So for blood flow, you should have said that vasodilation causes an increased blood flow to the skin surface, which increases heat loss through radiation, that body hair lies flat because the erector pili muscles relax, and this increases heat loss because that insulation layer of air cannot be maintained.

And then for other changes, sweat glands produce sweat, and this removes heat through evaporation.

So well done if you've got all of those correctly written.

Then I asked you to consider this scenario about putting an activated heat pack on your skin and what will happen to your skin in response.

So you might have written that your skin will appear pink and flushed because of vasodilation, and that's bringing blood flow to the surface of the skin so that heat can be lost through radiation.

And you also might have said that the body hair will lie flat because the erector pili muscles have relaxed.

And then finally, I asked you to consider this scenario about a person running a marathon on a warm day and what might happen if they don't drink enough water during the race.

So you might have said that because they haven't drunk enough during the race, they may stop sweating.

And this is because they've lost a lot of water and they haven't replaced it, and therefore they don't have any more water to lose in order to produce sweat.

So noticeably, they may well stop sweating.

However, the other thermoregulatory responses in terms of vasodilation and the erector pili function will not be affected because they aren't water dependent.

So check over your answer.

And well done if you've got that sweating explanation.

That was really very tricky indeed.

Okay, so we've come to the end of our lesson.

So what have we learned in our lesson today? Well, we've seen how human body temperature is maintained around 37 degrees centigrade in order to maintain body functions and our health, and that changes in our external environment can cause internal body temperature to change.

Now when our body temperature decreases, our body hairs stand upright, our blood vessels vasoconstrict, and these help to return our body temperature back to normal.

And conversely, when our temperature increases, we sweat and vasodilation occurs in order to return our body temperature back to normal also.

So I hope you've enjoyed our lesson today.

And I hope to see you again soon.

Bye.