Hello and welcome to this lesson from the unit, Hormones and human reproduction.

The title of today's lesson is Hormones: puberty, the menstrual cycle, and the menopause.

So we're going to start by looking what a hormone is, where it comes from and how it travels.

Then we're going to look about how it is involved in the menstrual cycle and the menopause.

My name's Mrs. Barnard and I'm going to be taking you through today's lesson.

So by the end of today's lesson, you should be able to explain the role of hormones in controlling puberty, the menstrual cycle and the menopause in humans.

And we've got some key terms in today's lesson.

And our key terms are hormone, gland, puberty, ovulation, and menstruation.

I'll just put the definitions up for you.

If you want to pause the video in order to write these down, you can.

Otherwise we'll be going through them as part of today's lesson.

So our lesson today is in three parts.

The first part is hormones, the second part is hormones in puberty, and then we are going to finish with hormones in the menstrual cycle.

So let's get started with the first part of today's lesson, which is hormones.

So the human body is made up of systems where the organs work together to carry out a particular function.

And the endocrine system is the system that is made up of glands and hormones.

And we can see in this image here, coloured in there is the glands.

We can see some other key organs there just so you can identify the area of the body.

So in grey, we've got the heart, the lungs, and the kidneys, and in the colours there, those are our glands that make up our endocrine system.

The job of the endocrine system is to regulate the body's many functions.

And those include things from mood, reproduction and metabolism.

Metabolism is all the chemical reactions that take place in your body.

So a gland is a group of specialised cells and they secrete hormones.

There are a number of glands that make up the human endocrine system and they're often part of a larger organ.

So we can see here in our our male and female images, we've got a pituitary gland, which is up there as part of the brain.

We've got the thyroid, then we've got the thymus, which is just above the heart.

We've got the adrenal glands, which just sit on top of the kidneys.

And then we've got the pancreas and then slightly different in males and females because we've got the testes in males and we've got the ovaries in females.

So what are hormones? These hormones that are secreted by glands.

Well, they are chemical messages and they are secreted into the blood and they're transported in the blood plasma.

So the blood plasma is the straw-like fluid part of the blood.

It holds things from digestion in there like glucose, amino acids and lipids.

But it also carries our hormones.

So it carries them through the circulatory system to target organs.

So if we have a look here, we've got our circulatory system and in the blood, and if we look inside the blood, we've got those cells that we recognise, red blood cells and white blood cells.

And then we've got the plasma and that's where the hormones will be carried.

So the hormones that are involved in puberty, reproduction, and the menopause are called sex hormones and they're released from the pituitary gland there.

And they can also be released from the ovaries and the testes because sex hormones are released from specific glands and they do differ in males and females.

So even though we've got the pituitary gland in males and females, in testes, in males, and it's the ovaries in females.

So hormones are specific to a target organ because the cells in the organ will have receptors on the surface that bind to that hormone.

Now this is because our hormones are travelling around in the blood.

So we might say, well, how do they know where to go? And the answer is, they don't know where to go 'cause they're chemicals, they just travel, they travel in the blood by the circulatory system.

And when the hormone attaches to a receptor that has a complementary shape on a specific cell, that will be only at its target organ and that is where it will have an effect.

So the complementary shape of the hormones and the receptor allows the hormone action to be specific, specific to a certain target organ.

So true or false hormones travel in the blood and so affect all organs.

Is this true or false? Now, once you've decided, you need to decide which of the statements below best justifies that answer.

So when you've had to go at that, come back and I'll tell you if you got it right.

Okay, so hormones travel in the blood and so affect all organs.

That is false.

And the reason is because hormones are complimentary to receptors on cells of target organs only.

So if you've got that right, then well done.

So now time for a quick practise task.

And we've got a confidence grid here.

So what I would like you to do is for each of these statements, I would decide, I would like you to decide whether you think it's correct or incorrect.

And then how sure are you? Are you sure it's correct or you think it's correct? Are you sure it's incorrect or you think it's incorrect? And then we'll check back and we'll see if you've got it right.

Okay then, so hormones are transported in the blood plasma.

This is correct.

They are secreted from glands and then carried in the blood plasma of the blood in the circulatory system.

The endocrine system removes waste from the body.

This is incorrect.

Some people might get it mixed up with the excretory system.

So the excretory system is the one that removes waste from the body.

Hormones are made by glands, hopefully everyone's got them.

That is correct.

And reproduction is controlled by sex hormones.

And that is also correct.

Remember those sex hormones that are made in the pituitary gland, the testes in males and the ovaries in females.

Okay, so now it's time to move on to the second part of our lesson, which is hormones in puberty.

So human children cannot produce offspring because their reproductive systems are not mature.

So as a child develops, the levels of hormones that are released from glands that are involved in sexual reproduction will change and that leads to sexual maturity.

So the process of these changes is called puberty.

Most females begin puberty between the ages of eight and 14 years, and most will finish within four years.

There's lots of variability in this.

So these are not hard and fast rules.

And in a male, they tend to begin puberty between the ages of a nine and 14.

And most males finish puberty within six years, so slightly longer.

Again, like I say, there's lots of variation in these.

The changes that happen during puberty are controlled by hormones, and the levels and timings of a hormone release may vary between different individuals.

So the start of puberty is activated by a part of the brain called the hypothalamus, and that's right in the centre of your brain.

And sex hormones are then released by the adrenal and the pituitary glands along with the testes in males and the ovaries in females.

So we've got puberty starting first before the other glands start to release the sex hormones.

And those are the ovaries in females and then the testes in males.

The changes that take place during puberty are controlled by hormones and prepare the body for reproduction and adulthood.

So they would take place in the male reproductive system, so the testes and the penis would get bigger.

The testes will start to produce sperm cells.

And in the female reproductive system we get the ovaries will start to release egg cells and then the menstrual cycle will begin.

Hormones will also control other physical and also emotional changes in males and females.

So these things include emotional changes, growth rate increases, stronger body odour, underarm hair will grow and pubic hair starts to grow.

But in males we've got separate things.

So they would be that the voice deepens and that the shoulders get wider and that the hair would grow on the face and the chest.

And in females we have that breasts develop and hips would widen.

So time for a quick check.

Select the glands that secrete sex hormones.

So pause video while you decide and then come back and I'll see if you've got it right.

Okay, so let's select the glands that secrete sex hormones.

So those are the ovaries and the testes.

So if you've got those right, then well done.

So time for a practise task.

So pupils are discussing puberty.

So Jun says, "Hormones are secreted by glands." And Jacob says, "Hormones control changes to the reproductive organs." And Lucas says, "Puberty starts at different times." And Sofia says, "Boys and girls develop differently during puberty." Now here each pupil has made a correct but quite simple statement.

So what I would like you to do is take each statement and add detail to it, including key words and further explanations.

So you'll need to pause the video to do this, and then when you come back we'll see if we can give you some feedback.

Okay, so let's have a look at these then.

So add detail to each of these correct statements.

So Jun said hormones are secreted by glands.

So we can add detail to this by saying sex hormones are secreted by pituitary and adrenal glands and the testes in males and the ovary in females.

So you need to include all the names of the glands in there to add detail.

And then for Jacob we've got that hormones control changes in the reproductive organs.

So we want to say that in males the penis gets larger and the testes starts to produce sperm.

And in females, the ovaries release eggs and the menstrual cycle begins.

So Lucas says puberty starts at different times.

So we can improve that by saying puberty is activated by the hypothalamus, sex hormones begin to be released.

And this starts at different times for different individuals.

And then Sofia said, boys and girls develop differently during puberty.

So we could improve that by saying in boys, the penis gets bigger and sperm is produced and their voice deepens and shoulders widen, and in females ovulation and the menstrual cycle begins, also breasts develop and hips widen.

So if you've got those right, then well done.

It's time to move on to the third part of our lesson, which is the menstrual cycle.

So the menstrual cycle involves processes that take place within the human female reproductive system.

Now you will have learnt about this when you are a bit younger.

So can you recall any of the reproductive organs? So I'll give you a few seconds to talk to the person next to you, you might want to pause the video while you do this and then I'll come back and I'll see how you got on.

Okay, so let's see if we've got them all then.

So we've got the ovaries there.

So those are our glands.

And then we've got the fallopian tubes and those fallopian tubes lead down to the uterus.

And then we've got the opening to the uterus, which is the cervix and the tube that comes down from there, which is called the vagina.

So if you've got all those right, then well done.

So the menstrual cycle that takes place in that reproductive organ.

And it is approximately a 28 day cycle.

So it's different for different people.

So it's not always 28 days, but often when it's modelled, it's modelled as 28 days and it prepares the adult female body for pregnancy.

And we can see that in this picture here.

We've got an egg entering the uterus there, ready to see if that is ready to implant.

It provides the right conditions for the offspring to be produced and to grow within the uterus.

So once a fertilised egg implants there in the lining of the uterus, then a foetus can develop.

Sex hormones control the menstrual cycles.

We've talked about these sex hormones already, and they control when this menstrual cycle takes place.

And these hormones are produced by the pituitary gland and the ovaries.

So those are the two glands that are involved in controlling this monthly cycle of events.

So we've got the pituitary gland there and we've got the ovaries there.

Hormone levels change during the cycle.

So all the way through this cycle, as it goes round round, the hormones levels change and that's what controls what is happening.

They are secreted into the blood and they travel to the glands in the ovary and the uterus.

So hormones control the processes of ovulation and menstruation.

Those are the two main processes in this cycle.

And the ovulation is when the egg is released from the ovaries and menstruation is when the uterus lining breaks down.

So let's look at this as a cycle.

So we often will start with one as the menstruation begins.

So this is when the lining of the uterus breaks down and leaves the body.

And then after it's left the body, that means that the egg hasn't been fertilised.

So therefore we're going to start this cycle again.

So then the uterus lining starts to regrow, ready for ovulation, which you can see occurs there at the bottom again.

So another egg is released.

If that egg is fertilised in the fallopian tubes, then it may become a zygote and an embryo and embed in the side of the uterus.

And then this process would stop, but otherwise it will continue.

And then the uterus lining will break down again.

And then this process continues.

So the menstrual cycle is controlled by hormones and it begins at puberty.

The menopause is when the menstrual cycle stops happening.

So it starts at puberty and it stops at the menopause.

And this occurs around the age 50, although some people it can be earlier or it can be later than that.

So we can see in this diagram here, we've got baby, toddler, child.

So puberty's going to start with a child and then it's going to end with an adult.

We've got the menopause in there between adult and elder.

And the menstrual cycle can occur during that period of time.

Changes in hormone levels during pregnancy cause the menstrual cycle to pause.

'Cause we don't want that uterus lining to be breaking down.

We don't want new eggs to be released.

So ovulation stops happening.

So we can see here, even though menstrual cycle occurs, it will pause during pregnancy and then again it will completely stop, which is a bit confusing 'cause the menopause has the word pause in it, but it will completely stop when you get to the menopause.

The levels of sex hormones at this point decrease because later in life, less of them are being produced.

And that means that the menstrual cycle will stop forever and that's what we call the menopause.

And after this point, a female can't become pregnant, therefore reproduction is no longer possible after the menopause has taken place.

So time for a quick check.

True or false, sex hormones control when the menstrual cycle begins and ends.

So once you've decided whether that's true or false, I'd like you to select which statement justifies your answer.

So pause the video while you do that and then we'll come back and we'll see if you've got it right.

Okay, so sex hormones control when the menstrual cycle begins and ends.

That is true.

And what justifies that is that sex hormone levels increase in puberty and decrease at the menopause.

So if you got that right, well done.

So let's have a look at our first practise task.

So what I'd like you to do is to match the keyword to the correct definition.

So we've got hormone, gland, puberty, menstruation, and ovulation.

So I'll give you a few moments to do that.

So pause the video and then check back.

Okay, let's see how you get on with that then.

So a hormone is a chemical messenger secreted by a gland and carried in the blood plasma.

A gland is a group of specialised cells that secrete hormones.

Puberty is the process of physical changes that lead to sexual maturity.

Menstruation is the process of the uterus lining breaking down, and ovulation is the process when an egg is being released from an ovary.

If you've got all those right, then well done.

Okay, so our second practise task is for you to write a description of hormone involvement in puberty, the menstrual cycle and the menopause.

So in your answer, I would like you to include the following key words, hormone, gland, puberty, menstruation, and ovulation.

So you'll need a little bit of time to do this writing.

So pause the video and then we'll come back and we'll look at your answer.

Okay, let's have a look at your answer to this one then.

So this is a model answer.

So sex hormones are chemical messengers released from the pituitary gland and the ovaries, also a gland.

In females, when they start to be released, puberty will begin and when the levels decrease, the menopause will take place.

Between puberty and the menopause, sex hormones will control the menstrual cycle, which includes ovulation and menstruation.

Menstruation is the breakdown of the uterus lining, and ovulation is the release of an egg from an ovary.

Now you might have written that in slightly different order.

It's just an example of how we can get all of our key terms there into our explanation.

So if you wrote a nice long detailed paragraph, then well done.

Now that brings us to the end of our lesson today on hormones, puberty, the menstrual cycle and the menopause.

So hormones are chemicals that are made and secreted by groups of specialised cells called glands.

Hormones are transported around the body in the blood plasma and detected by receptors on cells and tissues.

During puberty, hormones cause maturation of the sex hormones and development of secondary sexual characteristics.

Hormones control the menstrual cycle, in adult human females by causing ovulation and menstruation.

Decreases in hormone levels in older human females cause the menopause, after which the menstrual cycle stops.

Well done for your work in today's lesson and I'll see you soon.