Lesson video

Hi, I'm Mrs. Hudson, and today I'm going to be teaching you a lesson called the human endocrine system.

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 explain how the human endocrine system uses glands and hormones to control changes in the body.

There will be some keywords in today's lesson, and those are endocrine system, hormone, gland and receptor.

So let's have a look in a little bit more detail what those words mean.

The endocrine system is a system that regulates body conditions.

Glands secrete hormones into the blood that target specific organs.

Hormone is a chemical substance produced by a gland that travels in the bloodstream to a specific organ.

A gland is an organ or tissue that produces and secretes substances, such as hormones.

And receptor is a specialised cell that detect changes in the environment called stimuli and respond by stimulating electrical impulses.

If you need to pause the video now to make a note of those keywords, then please do, and then we'll carry on with the rest of the lesson.

Today's lesson on the human endocrine system is going to be split up into two different parts.

In the first part of the lesson, we're going to be looking at the endocrine system, and then we're going to follow that up by looking specifically at the endocrine glands.

So let's get going with the first part of the lesson, the endocrine system.

It is important that your body can react to changes in external and internal conditions.

The nervous and endocrine system work together to help regulate bodily conditions.

So for us to stay alive and healthy, our body is continuously responding to both external changes in the environment, but also changing environment within our body all the time.

And it's important that we are able to respond to changes in the external environment quickly, and also that conditions in our body stay relatively constant so that all of our organs can function as we need them to.

We're going to look now at the nervous system and the endocrine system very briefly, and the key differences between them.

So the nervous system acts quickly, sending electrical impulses along nerves.

The response is short-lived, and this picture here is showing you a basic outline of what makes up the nervous system.

So you've got the brain, the spinal cord, and then all the nerves as well.

The endocrine system secretes hormones from glands, which are slower to act on the body that's longer lasting.

You can see there's an image there of a female and part of the male body, which is showing you the glands of the endocrine system.

So the nervous and the endocrine system work together to maintain internal and external conditions, but the nervous system is very quick to act, but the response is short-lived and the endocrine system is slower to act, but much longer lasting effects.

The endocrine system is a complex system made up of glands and organs that secrete hormones.

The endocrine system helps to regulate metabolism, growth and development, the ability to reproduce, responses to injury, stress and mood, and blood glucose concentration.

And here we've got an image, the same image again that we saw in the previous slide, which is showing you female and male glands that make up the endocrine system.

Let's look in a bit more detail then about glands.

Glands are organs or tissues that produce and then secrete, which means release substances, such as hormones.

So we can see there, we've got our glands of the human body again, and they secrete hormones.

Those hormones travel in the bloodstream to get to the specific organ that they are trying to target.

Now, some organs are glands, but not all glands are organs, and we're going to talk specifically about some of the glands in the body later on in the lesson.

So a really important thing to think about is well, how do glands know when to secrete hormones? Receptors throughout our body detect changes in the environment, which are called stimuli and respond by sending electrical impulses to the brain, which in turn sends electrical impulses to the glands to trigger the secretion of hormones.

So this is where the nervous system and the endocrine system sort of link together.

So you've got receptors and they detect the change in the environment, that's called the stimuli.

And then electrical impulses are transmitted along neurons to the brain.

The brain then interprets those electrical impulses and transmits electrical impulses along neurons to the glands, and then this triggers the glands to secrete hormones.

Hormones are chemical substances produced by a gland that travel in the bloodstream to a specific organ and bring about an effect.

The effect that is brought about on your body is really important because that is the response to the stimuli.

So for example, if you have sensed that your internal blood glucose levels are too high, the effect in your body will be that your body tries to reduce those blood glucose levels.

If your body senses that you are becoming too cold, then the effect that will be brought about on the body is that your body will work to increase your temperature.

So if you have a gland, for example, the pancreas, one hormone that the pancreas secretes is called insulin, and the gland secretes that insulin and the insulin travels in the bloodstream, but specifically, it travels in the part of the blood called the blood plasma, and then the hormone is delivered to the target organ, which in this case is the liver.

And the liver will bring about an effect in the body.

In this instance, the pancreas has detected that blood sugar levels are too high, and so the hormone insulin travels to the liver.

And the effect that is brought about on the liver is that the blood glucose levels are decreased, the blood plasma transports hormones to their target organs where they then bring about an effect in the body.

So here we've got our secreting gland cell, which has got hormone inside of it, and then we've got the bloodstream underneath.

Target organ cells have specific receptors on their surface that bind to the hormone.

So if we show here, if that was the specific target organ cell, on the surface of that target organ cell, there is a receptor and you could also have a different target organ, but it's not the target organ for this particular hormone because it's got the wrong receptor.

So what happens is the hormone is secreted into the bloodstream.

Remember, it travels in the blood plasma and it travels through the bloodstream until it gets to the specific target organ, and the hormone binds perfectly with the receptor to bring about an effect in the body.

The reason the hormone doesn't bind with other organs is because the hormone is specific to the receptor on that particular target organ.

Changes in the body can be triggered by an increase and a decrease in the amount of hormone.

So here we've got a graph, which is showing you how the levels of oestrogen and progesterone, which we can see oestrogen is in the pinky colour and progesterone is in the blue colour, how they change during different parts of a female's life cycle.

So if we look specifically at puberty, when females go through puberty, there is an increase in the production of oestrogen and progesterone.

So during infancy, there's extremely low levels of oestrogen and progesterone, but then during puberty, those levels increase quite rapidly.

And then you can see through the reproductive years, the levels of oestrogen and progesterone remain high.

Females go through the menopause.

There is a decrease in the production of these hormones.

So the levels of hormones are changing throughout a person's life cycle.

Let's quickly do a check for understanding.

So this is a true or false question.

Hormones can bind to any target organ, true or false? And then justify your answer.

A, all target organs have the same receptors that hormones can bind to.

Or B, target organs have specific receptors that can only bind to one hormone.

So this is false.

Hormones cannot bind to any target organ, and the justification is that target organs have specific receptors that can only bind to one hormone.

Great job if you got that right.

Now let's do these quick questions.

So are these statements true or false? So these statements are electrical impulses are quicker to act than hormones.

Levels of hormones can change throughout a person's life.

Hormones secrete glands into the bloodstream, and receptors on the surface of organs can bind to any hormone.

So you need to say if those statements are true or false.

So the first statement, electrical impulses are quicker than hormones, that is true.

The second statement, levels of hormones can change throughout a person's life.

That is also true.

Hormones secrete glands into the bloodstream, that is false.

And remember, if you're going to correct that, it would be glands secrete hormones into the bloodstream.

And then finally, receptors on the surface of organs can bind to any hormone, that is also false.

Receptors on the surface of organs are specific, and hormones have to be specific to that one particular receptor.

Fantastic job if you got all of those right, well done.

We're now ready to move on to the first task of the lesson, and your job is to complete the table to show if the statement is describing the endocrine or the nervous system.

So the statement is made up of glands that secrete hormones, very quick acting, but short-lived response, messages delivered through electrical impulses and then slow to act, but longer-lasting response.

So is that the endocrine or the nervous system being described? Then for the second part of task A, you need to annotate the diagram below to show how the endocrine system brings about an effect on a specific target organ within the body.

And there are labels on that diagram there to help direct you what to write.

And then in the third part of task A, Jacob and Sofia want to learn more about the endocrine system.

Answer their questions in full sentences.

So Jacob with A is saying, "What is a gland?" And for B, "How do hormones travel around the body?" And then Sofia is asking the question C, "How does a gland know when to secrete a hormone?" I'm sure you're gonna do a really great job with this.

Pause the video and then press play when you're ready for me to go through the answers.

Let's see how we did them.

So with these statements, you had to say if it was the endocrine or the nervous system.

So made up of glands that secrete hormones, that's the endocrine system.

Very quick acting, but short-lived response, that's the nervous system.

Messages delivered through electrical impulses is the nervous system.

Slow to act but longer lasting response is the endocrine system.

So well done if you managed to get all four of those right.

For part two, we had to annotate this diagram.

So we've got the secreting gland cell there, and then inside of that is the hormone.

And then we've got the bloodstream, that is a specific target organ cell, and then the little blue label on the surface is the receptor.

And then we also have not the target organ cell because it has the wrong receptor.

So well done if you managed to label that diagram.

For question three, glands are organs or tissues that produce and secrete substances, such as hormones.

The endocrine system contains glands.

And then B, hormones are secreted into the bloodstream and travel in the blood plasma to their target organ.

And then for Sofia's question, so receptors in the body detect changes in the environment, which is called stimuli, and send electrical impulses to the brain, which then send electrical impulses to glands, triggering them to secrete hormones.

So that question there is showing you how the nervous system and the endocrine system can link together.

Really great job so far.

Well done.

So we know about the endocrine system now.

Let's look in more detail at the endocrine glands.

There are many glands located in the body that secrete hormones to help regulate conditions in the body.

And we've got this image, again, of the female and the part of the male body with the glands.

So we're going to look specifically now at the glands that you need to know.

So in the brain, there is a gland called the pituitary gland.

Now, this is also known as the master gland, and we're going to talk about why that is the case in a bit.

But the pituitary gland is located in the brain and then in the neck region, you've got the thyroid gland, then you've got the pancreas.

The pancreas is actually an organ in the body, so it has other functions as well, but it is an organ that secretes substances, which is why it is also a gland.

Then located at the top of the kidneys, you've got the adrenal glands.

You can see there's two of them, one sitting above each kidney.

And then the female reproductive glands are the ovaries and the male reproductive glands are the testes.

Let's quickly check our understanding.

So fill in the missing glands on this diagram.

So some of the glands have been labelled.

Can you label the missing glands? So the gland in the neck is the thyroid gland.

The organ labelled there is the pancreas, and the female reproductive glands are the ovaries.

And we've got the male testes ones labelled there.

So well done if you recognised those three glands.

Brilliant job.

Let's have a look in a little bit more detail about those specific glands and what they do.

So can you remember the name of the circled gland on this diagram? This is the thyroid gland.

The thyroid gland controls the metabolic rate of the body and secretes the hormone thyroxin.

Metabolic rate is the amount of energy used by an organism in a given period of time.

So metabolism is the sum of all the chemical reactions in your body, and the thyroid gland is involved in regulating the metabolic rate.

So here the thyroid gland secretes the hormone thyroxin.

Some people have problems with their thyroid gland, which then affects the metabolic rate of their body, and it can cause you to have medical health issues.

So it's really important that the thyroid gland functions effectively for you to be as healthy as you can be.

Can you remember the name of these circled glands? These are the adrenal glands.

So the adrenal glands are located at the top of both of the kidneys.

During stressful situations, the adrenal glands secrete the hormone adrenaline, which prepares the body for the fight or flight response.

Now, you may have heard of the fight or flight response.

If you're ever in a very scary or stressful situation, your heart might start to beat faster and you go a little bit shaky, that reaction is the result of adrenaline being pumped through your body.

And it is the adrenal glands that secrete the hormone adrenaline.

So the adrenal glands secrete the hormone adrenaline.

Can you remember the name of this circled gland? This gland is also an organ in the body, and it is the pancreas.

So the pancreas is an organ that also acts as a gland.

The pancreas secretes the hormones insulin and glucagon, which regulate the concentration of glucose in the blood.

So the pancreas secretes insulin and glucagon.

You might have heard of the term insulin before because some people have issues where their pancreas does not secrete insulin, and they have an illness, which is known as type 1 diabetes.

And this can be very, very dangerous.

So making sure that blood glucose levels stay within certain limits is very important.

Can you remember the name of the circled glands here? These are the ovaries.

The ovaries are a female sex organ that control the development of female secondary sex characteristics and play a role in regulating the menstrual cycle.

Secondary sex characteristics are characteristics that develop during puberty.

So this will be things like developing breasts, starting menstruation, developing facial hair in males or pubic hair in males and females.

One hormone that the ovaries secrete, which we have spoken about already, is oestrogen.

So ovaries secrete the hormone oestrogen.

Can you remember the name of this circle gland? And remember, this is the male gland now.

These are the testes.

The testes are the male sex organ that control the development of male secondary sex characteristics and the production of sperm.

The testes are involved in secreting certain hormones that develop the secondary sex characteristics, such as growing facial hair, growing pubic hair, but also, the testes are involved in the production of sperm as well.

One hormone that the testes secrete is testosterone, so the testes can secrete testosterone.

Now, you might have noticed that there is one gland that we have yet to talk about, and that is this gland here.

Can you remember what this gland is? It's found in the brain.

This is the pituitary gland.

Many glands in the body are themselves coordinated by the pituitary gland.

The pituitary gland acts as a master gland, so the master gland is the pituitary gland.

It secretes different hormones in response to changes in body conditions.

These hormones then act on other glands to secrete further hormones.

So we've got two examples here of the pituitary acting as a master gland.

So the pituitary gland can secrete a hormone called follicle-stimulating hormone, known as FSH.

And FSH affects the ovaries, and it indirectly causes oestrogen levels to rise.

So the pituitary gland has an effect on the ovaries.

Another example is that the pituitary gland secretes a hormone called thyroid-stimulating hormone, known as TSH, and TSH then acts on the thyroid gland, which stimulates it to make thyroxine that helps control metabolism.

So in this example, the pituitary gland is having an effect on the thyroid gland.

Let's quickly check our understanding.

So true or false question.

The pituitary gland is known as the master gland, true or false? And justify your answer.

A, the pituitary gland secretes hormones that act on other glands to secrete different hormones.

Or B, the pituitary gland only secretes one hormone that does not target any other glands.

So this is true, and the justification is A, the pituitary gland secretes hormones that act on other glands to secrete different hormones.

And then let's have a go at matching the glands to the hormone that it secretes.

So the glands we've got are the testes, pancreas, ovaries, thyroid, and adrenal glands.

And the hormones are A< insulin, B, thyroxine, C, adrenaline, D, oestrogen, and E, testosterone.

So have a go at matching those up now.

So insulin is secreted by the pancreas, thyroxine is secreted by the thyroid gland, adrenalin is secreted by the adrenal glands, oestrogen is secreted by the ovaries, and testosterone is secreted by the testes.

So fantastic job if you've got those right.

Well done.

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

So in the first part of task B, you need to label the diagram to show the glands of the endocrine system.

Then for part two, you need to complete the table to show the hormones secreted by different glands and their role in the body.

So you have the gland and the hormone that they secrete and the role in the body, and you just need to fill in those blanks in the table.

And then finally, for part three, using the diagrams, explain why the pituitary gland is known as the master gland.

And you've got a picture there of the two examples that we spoke about.

I'm sure you're gonna do a fantastic job.

Pause the video, give it your best go, and then press play when you're ready for me to go through the answers.

Let's see how we did.

So labelling the glands in the endocrine system, the gland in the brain is the pituitary gland.

You might have also have written there that that's the master gland, but do make sure you have got pituitary written down.

Then in the neck, you've got the thyroid gland.

The organ is the pancreas, which acts as a gland.

And then sitting above the kidneys, you've got the adrenal gland.

The female reproductive glands are the ovaries and the male reproductive glands are the testes.

So well done if you manage to get those right.

Filling in this table, the thyroid gland secretes thyroxine, and its role in the body is that it controls the metabolic rate of the body.

Adrenaline is the hormone secreted by the adrenal glands.

Oestrogen is secreted by the ovaries and its role in the body is that it controls development of female secondary sex characteristics and the menstrual cycle.

Testes, they secrete the hormone testosterone.

And insulin is secreted by the pancreas.

And the role of insulin in the body is that it regulates blood glucose concentration.

Fantastic job if you got those right.

And then finally, moving on to the third part, so why is the pituitary gland known as the master grand? And then give examples of why that is the case.

The pituitary gland secretes hormones that then act on other glands to secrete different hormones, bringing about an effect on the body.

And the two examples that we spoke about with the pituitary gland secreting FSH, which is follicle-stimulating hormone, which indirectly causes oestrogen levels to rise.

And then the pituitary gland secretes TSH, thyroid-stimulating hormone, which stimulates the thyroid gland to secrete thyroxin.

Fantastic job if you managed to answer all of those questions, I'd recommend pausing the video and going back just to check you've got all the detail in your answers that you need.

But we're going to move on next to summarise everything that we've learned in the lesson.

So today we have been looking at the human endocrine system, and we said that the human endocrine system consists of glands that secrete hormones into the bloodstream that target specific organs and bring about an effect on the body.

Receptors detect changes in the environment and send electrical impulses down nerves to the brain, which in turn send electrical impulses down motor neurons to glands, triggering them to release hormones.

And some glands that make up the endocrine system are the pituitary gland, the thyroid gland, adrenal glands, the pancreas, ovaries, which are female, and the testes, which are male.

And then finally, we looked at the fact that the pituitary gland is known as the master gland as its secretes hormones that act on other glands, triggering them to secrete further hormones.

The two specific examples we talked about were the pituitary gland releasing FSH and the pituitary gland releasing TSH as well.

I've really enjoyed today's lesson.

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