Lesson video

This lesson is called the human nervous system and is from the unit coordination and control of the human nervous system.

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.

In our lesson today, we're going to describe the parts that make up the human nervous system that enables us to sense and respond to changes.

Now, we're gonna come across a number of keywords in our lesson today, and they're listed 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 have a look at the nervous system first before we look at the pathway through the nervous system.

So you ready to go? I am.

Let's get started.

Now, we know that the human body is a really complex collection of very specialised cells and systems, and they are all adapted to help us to survive and thrive within the world around us.

So there's many different specialised cells and systems. I'm sure you can think of a good number.

Things like cardiac muscle and skin cells, lung tissue and organ such as the brain and the heart, and systems such as the digestive system, the reproductive system, and the nervous system.

So information about our internal and our external environment is gathered, processed, and acted upon by the nervous system.

So it's gathering all this information about what is going on around us, both inside us and outside us, coordinating it in a central place and enabling us to respond effectively to it.

So the nervous system allows the brain to control and oversee all of those processes and monitor every single aspect of the body and its function.

So the brain is controlling everything.

It has absolute oversight over everything that is going on inside our body.

Now the nervous system is divided into two main sections.

The central nervous system includes the brain and the spinal cord, and you can see them in yellow on the diagram here.

And then the peripheral nervous system is everything outside of that.

So that's all the parts of the nervous system down to our fingertips and down to our toes, and they're shown in blue on the diagram.

So the central nervous system is the core part, the brain and the spinal cord, and the peripheral nervous system is everything else.

Now, the nervous system includes, well, those two sections, but let's look at that in more detail.

So it includes the brain, which is what is processing messages and coordinating the responses.

Some of these parts are being done consciously, so we're in control of those decisions that the brain is making, and some of those things are ticking along in the background unconsciously that we don't really have any control over, the brain is just overseeing them regardless.

Then the brain is connected to the spinal cord, and this is a really dense column of nerve cells that connects the peripheral nervous system to the brain, and that's part of the central nervous system.

Then we have a collection of nerve cells, also known as neurones, and these transmit electrical impulses between different parts of the body.

So these are relaying messages from one part of the body to another part of the body, and these messages are being transferred in an electrical format.

And then finally, we have sensory receptors, and these are auto detecting changes to our environment, be those changes happening within our body or outside of our body.

So these are the parts of the nervous system, the brain, the spinal cord, neurones, and sensory receptors.

So let's just check our understanding.

Which of the following parts are part of the central nervous system? The brain, sensory receptors, and the spinal cord.

What do you think? I'll give you five seconds to decide.

So hopefully you've identified that parts of the central nervous system include the brain and the spinal cord, remembering that sensory receptors are part of the peripheral nervous system.

Did you get those two right? Well done.

So what I'd like you to do is just summarise this first part of the lesson by first of all labelling the diagram with the central nervous system and the peripheral nervous system.

Then I would like you to complete the table to describe the parts of the nervous system and their general function.

So are the brain, spinal cord, neurones and sensory receptors, part of this central nervous system, the CNS, the peripheral nervous system, the PNS, or both? And what are their functions? So pause the video and come back to me when you're ready.

Okay, let's see how you got on.

So on the diagram, I asked you to label the central nervous system.

So that's the brain and the spinal cord.

And the peripheral nervous system, that's every other part of the nervous system, which does not belong to the central nervous system.

Now, your label arrows might well be located in slightly different locations, but do make sure they're pointing to the right parts of the nervous system.

Then I asked you to complete the table to describe the parts of the nervous system and list their general functions.

So the brain is part of the central nervous system, the CNS, and its function is to process messages and coordinate responses.

The spinal cord is part of the CNS, and it is a dense column of nerve cells that connects the peripheral and the central parts of the nervous system together.

The neurones are found in both the CNS and the PNS, and their function is to transmit electrical impulses between different parts of the body, and then those sensory receptors are found in the PNS, the peripheral nervous system, and their function is to detect changes in the environment.

So just review your work over, make any amendments if you need to, and well done.

So let's have a look now at how we move changes in our environment from the sensory receptors through to the brain and back again, the pathway through the nervous system.

So we know that sensory receptors are located in the peripheral nervous system, and we also know that they can detect changes in the environment.

Now we call these changes in the environment a stimulus and sensory receptors are sensitive to stimuli.

So let's look at some examples.

An internal environment stimulus could be, for instance, an increase in body temperature.

If we look at a cross-section of the skin, we can see that the outerlay of the skin is at the top of the diagram with the hair sticking through it.

Then underneath that are layers of other skin, and then beneath that is a layer of fatty tissue, that's the yellowy blobs.

And then there are a number of other parts within that skin cross-section.

So changes in the body temperature will be detected by a single sensory receptor in the skin and you can see that labelled on the diagram, that light green P-like shape, that's the skin temperature receptor, and that will detect changes in the skin temperature.

And this is a single sensory receptor.

It's one on its own, not operating with any of the others.

There's lots and lots of them distributed across our skin, but they operate on their own and they are operating to detect changes to our internal environment.

An external example might be a change in light intensity.

So if we're talking about light, then we're talking about the eyeball and the eye is detecting light using a group of very sensitive receptors found within the retina.

Now these are a collection of receptors and they work together in order to build up a picture that is comprehensive and seamed together rather than seen as individual pixels.

And these are detecting an external stimulus, light coming from the outside.

So the sensory receptors receive their signal, be that from an internal stimulus or an external stimulus, and they pass their information on to the sensory neurones.

So the receptors are located at the end of the sensory neurone and trigger a message, an electrical impulse to be fired down the sensory neurone.

So the sensory neurone is connecting the receptor at one end to the central nervous system in the spinal cord at the other end.

So the sensory receptor is passing that message onto the sensory neurones, and that message is relayed along the sensory neurone to the central nervous system.

Then, at the central nervous system, at the spinal cord, that message is transferred to a relay neurone and there are many relay neurones connected one after another.

And these connect the spinal cord up to the brain and then the brain can process that information, coordinate a response, and send a message back down towards wherever part of the body is needed to respond.

And this coordination and control is all being done through relay neurones.

Then at the spinal cord, the relay neurones connect with motor neurones.

So this diagram shows a motor neurone and at one end it will be connecting to a relay neurone, and at the other end, it'll be connecting to something that is going to take action.

So motor neurones transmit electrical impulses through the peripheral nervous system.

We're back out of the central nervous system, and once again, back in the peripheral nervous system.

Once the message has reached the end of the motor neurone, it's arrived at the effector and the effector will have the effect.

Now, an effector might be a gland, for instance, a sweat gland within our skin that increases sweating in response to the increase in temperature detected by the sensory receptor and helps to cool our body down.

So that's an example of an effector, a gland.

Another example is a muscle.

So in response to changes of light intensity, a muscle might be triggered.

The ciliary muscles in the eye might be triggered to contract, which makes the pupil, that's the black bit in the middle of your eye, smaller so that less light can get in, and that will help to protect the eye and manage the light levels being received by the back of the eye.

So an effector could be a gland or it could be a muscle, but either way, it's being triggered by a motor neurone in order to act and respond accordingly as coordinated by the brain.

Now we can put that whole process into a flow chart to see how we go from one end to the other.

So one detection of a stimulus, the sensory receptor passes that information on to a sensory neurone, and the sensory neurone transmits that electrical impulse along to relay neurones in the brain.

Those relay neurones in the brain coordinate the response and then pass that message out to the motor neurones, which electrically transmit that information to the effector and the effector causes a response.

So we've got this very clear flow chart.

It's multi-parted because there are lots of different neurones taking part in this process, but it's also very straightforward.

Sensory receptor to sensory neurone, relay neurones to motor neurone to effector.

So starting with the first, what I'd like you to do is order these parts of the nervous system to show how a stimulus can trigger a response.

The parts include the effector, the sensory receptor, the motor neurone, and the sensory neurone.

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

Okay.

So you should have started off with the sensory receptor, then moved to the sensory neurone, followed by the motor neurone, and then the effector.

And of course, the bit that we are missing is the renal neurone between the sensory neurone and the motor neurone.

Now did you get those right? Well done if you did.

So what I'd like you to do now is to just collate and summarise that information by, first of all, creating a flow chart to show how a message moves through the nervous system from sensory receptor to the effector organ on detection of a stimulus.

So a bit like that flow chart we've just looked at.

Then I would like you to complete the pathway to show how you'd pick up a pencil having seen it, starting with the pencil as a stimulus, then showing me which neurones we would go through, and then picking up the pencil, which is the response.

Then finally, I'd like you to consider this scenario.

So when a frog sees a fly, it fires its tongue out to catch the fly.

So can you describe the pathway from sensing to responding, including the roles of the fly and the tongue in this process? So pause the video and come back to me when you're ready.

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

So firstly, I asked you to create a flow chart to show how a message moves through the nervous system from sensory receptor to effector organ.

So you should've started off with a receptor, then gone onto the sensory neurone, then shown that there's a number of relay neurones in the brain, then the motor neurone, and then the effector.

So just check that you've got them in the right order.

Then I asked you to complete the pathway to show how you'd pick a pencil having seen it.

So the pencil is the stimulus, that moves on to the sensory neurone, then the relay neurones, then the motor neurone, and then the effector muscle, which allows us to pick up the pencil, which is the response.

So again, just check you've got those in the correct order.

Then finally, I asked you to think about this scenario that when a frog sees a fly, it fires its tongue out to catch the fly.

And what I wanted you to do was to describe the pathway from sensing to responding and include the roles of the fly and the tongue in that process.

So you should have said that the fly is the stimulus.

It's triggering the sensory receptors to send an impulse.

The sensory receptors transmit the electrical impulses to the relay neurones in the central nervous system.

Then you should have said that the brain processes this information and sends an electrical impulse down the motor neurone to the tongue.

The tongue is the effector.

So it receives the message to act and carries this out to catch the fly.

So just check that you've got the tongue and the fly correctly identified, and you've got the process properly laid out within this scenario.

Well done indeed.

Okay, so in our lesson today, we have seen that the nervous system enables us to detect changes in our internal and external environments and respond quickly to these changes.

So a stimulus triggers a receptor, and then that message is sent to the brain via sensory neurones in the peripheral nervous system, whereas the brain and the central nervous system then coordinates that response, sending an instruction to the effector, which might be a muscle, or it might be a gland via the motor neurones to trigger a response.

So thank you very much for joining me.

I hope you've enjoyed our lesson today, and I hope to see you again soon.

Bye.