Anatomy of CNS wk 9 s2

So we're shifting from physiology to anatomy. It's still going to make this a little easier. The physiology I find quite hard so it's quite raw, heavy. So this is easier but there is still quite a bit of it to cover.

Okay super right we are recording. So we are going to be covering in this session then the anatomy. So that's the structure of the central nervous system. We're going to start off by looking at the meninges of the cerebral spinal fluid then we'll look at the brain and we'll finish off with the spinal cord. Next week we'll be moving on to the anatomy of the peripheral nervous system and then we'll be looking at the spinal nerves, the cranial nerves and the autonomic nervous system. Okay you just start the central nervous system then.

It consists of the brain.

The brain weighs around 1.4 kilos and then the spinal cord. Now the spinal cord runs from the base of the brain but notice it only runs down to about L1, L2. L1, L2 is around here in my back.

Your spinal cord does not run down to the bottom of your spinal column. Okay so this is something slightly different to what we think of at school. You normally think the brain goes from spinal cord going from top to bottom but it doesn't. It runs from the base of the brain down inside the vertebrae. Down as far as about L1, L2. The central nervous system is protected.

The central nervous system is protected. It's protected by the bones so we've got the bony skull. The brain is with inside that bony skull. It provides quite a lot of protection but it does cause some problems too as we'll see. The spinal cord is protected by the vertebrae so it runs within a hollow tube down the centre of the spinal bones, the vertebrae. And then the meninges are our membranous coverings that cover the brain and spinal cord. So if we look, are we all right up at the top there?

All okay? Any questions?

Any questions? No? Okay then. So if we look at a cross section of the spinal cord at T7 we can see we've got the spinal cord making that plastic butterfly shape here. If we do a cross section at T12 here you can see the spinal cord in the middle but surrounding it we have peripheral nerves, peripheral nerves that'll make more sense in a bit. If we do a cross section at L2 below the level of the spinal cord then this is where all we see we no longer have any spinal cord but we've just got lots of peripheral nerves. They're all going to go down to the legs.

Okay? Right, so that's our overview of the brain and spinal cord. Let's start with the meninges. The meninges are these membranous coverings that cover the brain and the spinal cord and it's made with three layers. The dura mater, the arachoid mater and the pia mater.

Dura mater, arachoid mater and pia mater. Now these are named in Latin so mater means mother.

Dura means tough, tough mother.

Pia means soft, soft mother, very dead, very good and soft. Arachoid means like spider webs.

Okay? So tough mother, spider webs and soft mother. The tough mother there, dura mater, is a thick, tough membrane.

If we look at the picture here, in dark gray this is the bony skull. So we're coming inside the brain, inside the skull, from boniness on the outside, directly under the fat there we have this layer of dura mater. The dura mater is made up of two layers.

It's got a peristal layer, which is the layer that's closest to the bone and then the bony dura layer, which is the layer that's closest to the brain. In fact, we'll see why these are important. The arachnoid mater is a bit like a spider's web.

The arachnoid mater is a bit like a spider's web. So in the picture here it's this kind of dark pink with all these blood vessels in here. So it's the spider web appearance and it's provided by that blood-brain barrier. So it's impermeable to the fluid. And then lastly, the pia mater is the layer that's the closest to the brain tissue itself. So in pale gray, it's actually brain. So the pia mater is this palest pink in the cartoon and that's sticky and it goes over every lump and lump. So it follows the shape of the brain down the spinal cord, all the way down, covering the whole of the central nervous system. So why are we bothered about the ninjis?

So why are we bothered about the ninjis? Why is it that they're important? And one of the reasons is about bleeds. So bleeding inside the skull.

As I said, the skull is great because it provides a bony protection for the brain. But the problem is there's nowhere for lumps and bumps to expand.

You get a boomer on your arm, it swells up, it's no problem, it just swells up. You get a boomer in your brain, there's nowhere for it to swell up to go to. It's stuck within your bony skull. So that causes a big problem because it puts pressure on parts of the brain. Now bleeds, which will cause pressure on the brain tissue, can either be subdural, so here's a picture of a subdural one. So this is a bleed that's underneath the dura mater, so it's a bleed that's under the dura mater or between the two layers of the dura mater. Now if you have a bleed that's subarachnoid, it doesn't get trapped within a little pocket. It spreads all the way around the brain, so it now squashes the whole brain. Whereas a subdural bleed will compress one patch of brain, a subarachnoid bleed will squash the whole brain. So these will cause different symptoms, won't they? Because we'll get the symptoms of squashing one little bit versus the symptoms of squashing the whole lot. An intracerebral bleed is a bleed actually within the brain itself, and again that's going to squash specific bits of brain tissue, causing specific symptoms. Another technical problem with the meningitis is meningitis.

So meningitis is inflammation of the Now you guys will have heard of it, I'm sure, because of infectious meningitis.

So either bacteria or viral infections that can cause inflammation of your meninges.

These can be really very very serious and they're ones to get self-optile hospital with.

So it used to be that students were at risk and it spread through halls and that kind of thing. These days they're looking around to talk to them these days, don't they? So don't know what's going on there. But meningitis is not only caused by infectious agents, it can be caused by other things as well. So things like cancer treatments, chemotherapy can also inflame the meninges. The epidural space.

I'm sure lots of you have heard of people having the epidural. For example, when having a baby, sometimes with a pain ring you can have an epidural, you can have drugs, put into, as that is put into, the epidural space.

So the epidural space is the space between the duramata and the surrounding tissues.

So outside of the duramata.

In the picture here, it's the one with the blue needle. So here's our syringe going in. It's going to go in, typically an epidural goes in between L3 and 4. Here it's gone in between L2 and 3. And it's going into the space outside of the duramata.

So between the duramata and the tissues, the ligaments, the tendons, the muscles and so on.

And this then provides an aesthetic effect to all of these peripheral nerves that are kind of in this area.

So it knows things below that level. The subarachnoid space is the space between the arachnoid martha and the pyramata.

So between those two layers. And what's important about that is it's the area that's filled with cerebrospinal fluid.

The pyramata follows the surface of the spinal cord and then this terminal film all the way down.

The arachnoid martha is on the outside of that.

So the gap between is our subarachnoid space.

This is filled with cerebrospinal fluid. So if someone needs a lumbar puncture, if someone needs a sample taken out of their cerebrospinal fluid to look for something like meningitis or other problems, they usually go in with a needle, usually just a bubble below l4.

So here they've gone between the vertebrae l34 into that area where the fluid is. The reason they've chosen this level is because it's below the bottom of the spinal cord. You don't want to be putting needles in that might actually hit the spinal cord. That would cause proper damage.

So instead you go lower than the end of the spinal cord and we try to remove a little bit of fluid. So that leaves us nicely on to the cerebrospinal fluid. So this is a clear colourless liquid.

It's pretty similar to plasma, blood plasma, but a little bit weaker. So it's got things like water, salt, glucose, plasma proteins. It often has just a few white blood cells, but it shouldn't have many white blood cells in it. The average adult has about 150 milliliters of cerebrospinal fluid. You produce about 720 men a day and it flows.

We'll see where it's produced in the brain and it flows around the brain, around the spinal cord and then it's reabsorbed into our blood system. So it's constantly being produced and absorbed, produced and absorbed. So the fluid is changing over about every eight hours.

The purpose of our cerebrospinal fluid is to cushion the brain. So it provides a bit of a shock absorber when we move our heads around. Our brain doesn't rattle too much because of the fluid.

They even the outside of the brain and also it's able to transport nutrients, providing the nervous system with important nutrition and removing waste products. And then it also helps maintain a constant pressure in the brain. So we don't want the pressure in the brain to become too great or too small.

too small. If I go back to this slide here, where we've got these swellings, because the scar is bony, what do you think happens when we have too much pressure in the brain? What happens if someone's got a bony on the brain or pressure?

pressure? What holds have we got in the house of skull? So sometimes fluid leaks out through nose, ears, eyes, things like that. So that sometimes there's fluid leaking like fleas. But if it's just a pressure build up, where is the biggest hole in the brain? In the skull, sorry, in the skull.

It's the bit that's going to let the spinal cord come out, isn't it? At the base of the skull, there's a hole of the magnum foramen. See, please, an egg magnum.

Big hole, magnum foramen. And that's where your spinal cord comes out. So when it's swelling on the brain, it's going to push the brain down the magnum foramen. And it pushes the brain stem down.

The brain stem, as we'll see in a minute, is important for core basic functions.

So if we push our brain stem down as there, it affects those basic functions. It makes them act like a drunk.

So pressure in the brain triggers symptoms very similar to slurring that kind of problem.

So having a bony skull is brilliant, but does cause some problems. Okay, so the cerebral spinal fluid helps as we're maintaining that constant pressure. But if we find cerebral spinal fluid leaking out of our ears or our noses, that's usually a very bad sign, very bad editing.

We produce cerebral spinal fluid in the ventricles.

Now the ventricles are cavities, hollow cavities, holes within our brains. They're not holes are such because they have to be filmed in the fluid, but they are holes within the brain tissue itself. And we have four of these ventricles, these irregular shaped cavities.

We have two lateral ventricles. You can see those here. These are our lateral ventricles. If we look side on, here they are, they form a C shape.

And it's these lateral ventricles. It's where the cerebral spinal fluid is produced. So the cerebral spinal fluid is produced by an ependymal cell.

We talked about the neuroglia, we had astrocytes, we had oligodendrocytes, ependymal cells, and something else, microglia. So ependymal cells were the ones that produce the cerebral spinal fluid. So they line our lateral ventricles.

From the lateral ventricles, that fluid is produced in the lateral ventricles, it then drains into the third ventricle, the third ventricle. From the third ventricle, it drains into the fourth ventricle.

And from the fourth ventricle, it goes down the center of your spinal cord, down the central canal. So as you can see from this picture, to get from each of these ventricles to the next one, there are narrow gaps.

So to go from the lateral ventricle to the third ventricle, the gap here is tiny. Look, little gap just here, to go from the lateral ventricle into the third ventricle. This is called the intraventricular forraforming act. To go from the third ventricle to the fourth ventricle, it has to go through what's called the cerebral aqueduct.

Now, anywhere where you get narrowing is a potential pinch point, isn't it? It could get blocked and then it causes a problem because if we can't move the fluid around, problems.

From the fourth ventricle, it goes down that central canal.

So the central canal of the spinal cord, or it can head into the subarachnoid space.

We'll look at that in a cord.

So here's another picture of the same thing here. Okay, we've got in our photo here, it's not as easy to see in pale blue. This is where our cerebral spinal fluid is produced, the lateral ventricles.

It then flows into the third ventricle. From the third ventricle, it comes down through that cerebral aqueduct into the fourth ventricle.

From here, there are different choices.

It could go down the central canal of the spinal cord, all the way to the very bottom. At the bottom of the spinal cord, it comes out and it can travel back up the outside. So it can go up around the outside.

When it gets back up to the brain, it then goes around the outside of the brain.

And from here, it drains back into the venous circulation.

So it rejoins the venous, our deoxygenated blood, our venous circulation, what's called venous sinuses. The venous sinuses then drain into the jugular.

The venous sinuses then drain into the jugular. So the jugular is our main vein coming down my neck. 30 second video, I don't even remember what it was. Let's see if it's an interesting one. What have I suggested?

What have I suggested? The adverts move longer than the 30 seconds, isn't it? Okay, so here's it being produced. So the fluid being produced, traveling into the third ventricle, the fourth ventricle, it goes.

the fourth ventricle, it goes. The screen cut out. Oh, for goodness sake, really? Is it because I'm watching YouTube?

Is it because I'm watching YouTube? It is, it doesn't like me watching YouTube. It's nothing daunting.

Right, let's watch it again.

Okay, it's being produced by the lateral ventricles.

It flows into the third ventricle, down to the fourth ventricle. It can go down the spinal cord and then back up the outside, around the outside of the brain, where it then drains into the venous, the superior sash of the sinus, the venous blood vessel there. Okay, there we go.

So hopefully useful to see how cerebral spinal fluid is produced. It then ends up in our venous blood. So it disappears, which is why we then need to produce more.

It drains through the pores. We have to constantly produce it, constantly flowing. These venous blood vessels there, the venous system where the cerebral spinal fluid is draining into, they're specialized veins because they're dead-ended veins.

veins. They're not, normally, we have arteries, capillaries, veins, don't we?

don't we? This just starts with veins. There's no capillary, it just starts with blind-ended veins.

So they're called venous sinuses and they're formed where the durumata separates.

Do you remember we had the durumata was made of two layers.

So in some ways it separates out and we can see that in, I've added a little extra, it's not in your downloadable version, but this is on my version here, in grey this is our durumata. So the two layers of the durumata come apart and now venous blood can pool in the gap and we get these form in specific places. So we have what's called the Fox cerebras. So it's a gap that forms down the centre of our skull or centre of our brain rather. So it forms the superior fascia sinus, a blood vessel, a vein that runs down the centre.

The Fout cerebelli is the same but in for the cerebellum. So it sits just between the two sides of the cerebellum and then the Tenterum cerebelli forms these sideways ones. The little gaps between the cerebrum and the cerebellum.

So we end up with little pockets there that form those venous sinuses.

So the cerebrospinal fluid drains into these sinuses and then eventually comes down the neck into the jugular vein. From the jugular it then is going to go into the superior cava and into normal circulation.

So that's our venous circulation for the brain.

circulation for the brain. What about arterial circulation then?

circulation then? Well the brain gets about 15% of our cardiac output so it's quite a high priority for blood and oxygen. Not as high as some areas that we saw seen earlier in the module but still pretty high.

It needs a constant supply of oxygen and glucose and just like the kidneys have auto-regulation to regulate the pressure, the blood pressure in the brain. So if blood pressure goes up it automatically dilates some of the vessels. If blood pressure goes down it automatically contracts them trying to keep the flow going through the brain.

And we have what's called the circle of willis.

This is our circle of willis. So the circle of willis sits underneath. This is our view looking up from the neck looking up at the brain and it looks like a little leg area. So we've got our head with antennae and two eyes. We've got a body and we've got some legs and some arms.

The key thing to highlight here is this circle.

It's a circle a bit like a ring road. This means that if I block part of the circle it means that that bit of rain will not be starved of oxygen because the blood can just go the other way or around the circle.

So even if we ruin the blood the other way around.

ruin the blood the other way around. It's a safety feature. So the circle of willis. Okay true or false?

Okay true or false? The epidural space lies between the duramata and the arachnoid matter.

True or false? False. So it's outside of the duramata.

The subarachnoid space lies between lumbar punctures carried out around l4 to remove cerebral spinal fluid from the epidural space. It's carried out around l4 but it's removed from the subarachnoid space.

So near. Okay 20 seconds decompress and then run to the brain.

Okay so a little short break 20 seconds maybe 30.

Let's do 30. Okay so the next section moves on to the brain. Now the brain can be divided into different regions in different ways. Our core textbook Ross and Wilson which is actually written by Warren Brand. It always confuses me. Warren Brand written with Ross and Wilson.

This book our core textbook divides the brain up into the cerebro the diencephalon and the brain stem and cerebellum.

So here's our cerebro the big bit. Diencephalon is deep inside the brain.

The brain stem is where it attaches to the spinal cord and the cerebellum is the cauliflower sticking out the back.

Just to be awkward I'm not going to divide it that way. I'm going to divide it up slightly differently to the textbook. Okay you can see why.

Aspen archipelae that's our book for those who want the more animal side of things. They divide it up into the forebrain which is the cerebro the midbrain and the hindbrain. We're going to divide up by function.

So we're going to divide it up into cerebro which is what the limbic system and the central core. So not quite what the textbook does.

So functional regions the cerebro is the area of the brain that is well developed in primates.

So for primates this is where we're going to get all the functions that we could do more than other mammals like a sheep. Things that we do differently to sheep that's probably going to come from the cerebro. The limbic system is well developed in all mammals.

So the limbic system includes things like the hifers, the hippocampal, the nipza and the cingulate cortex.

This is well developed in all mammals. So if you think about sheep and cats and dogs as well as us. The central core is well developed in all vertebrates.

So this includes things like reptiles. So the central core provides those functions of life which are relative and that's to be found in reptiles as well as mammals as well as primates and humans.

So the central core is our brain, stem, thalamus and the cerebro. So we'll look at each of these in turn. Let's start with the cerebro then.

It's the largest part of the human brain. So here's a picture of the human brain and then the size of comparison we've got different animals. We've got an elephant brain which is really not much bigger than a human brain because during a size difference an elephant is massive.

Dolphin brain similar size to ours.

Gorilla, fair bit smaller. Dog, cat, mouse and that's a macaque, another type of monkey.

We can divide the cerebro into two hemispheres from the left side and the right hand side.

The gyri are the lumpy bits, the ridges, the bits that bump up, they're called gyri. Whereas the sulci are the grooves, the dips. So the surface of the brain is opey bumpy so we've got gyri and sulci, gyri and sulci and this causes a big surface area and it's the surface area is one of the factors that seems to contribute towards intelligence.

So intelligence is not just linked to size because we can see that the human and the elephant sizes are similar but the argument would be that humans are more intelligent. You can either agree or disagree with that, it's up to you. But look at the surface area difference.

Our sulci are much deeper so we've got a bigger surface area, we've got more gyri, more sulci that give us that more surface area.

Dolphins have got quite a lot of these grooves so they have got quite a lot of surface area which might tie in with the fact they are quite intelligent.

Look at the cat brain, not much surface area. I love my cat to pieces but not the most intelligent being in the world. Fishes are deep grooves.

Can you see along the central line? This is where we get fishes, where we get much deeper grooves and that's where we've got the biggest sizes for them, we've got gaps to enough space for those veins to actually form. Human brain not only does it have a bigger surface area, it also has the highest neuron or density in the cerebral cortex, it also has lots of highly myelinated neurons. So we have very fast neural networks.

very fast neural networks. So it's not as simple as size, it's not as simple as lumpy bumpiness, there's more to it than that. But these things that contribute towards supposedly better intelligence. If we look at that cerebrum then, we can divide it into different areas. The cerebral cortex, the cerebral nadala, corpus callosum and the basal ganglia. Let's start with cerebral cortex. The cerebral cortex is the outer gray layer, the gray matter layer. We've met this already, haven't we?

haven't we? We have gray matter following the lumps and bumps, following those gyrin sulci, all around the outside of our cerebrum.

So this is known as our cerebral cortex, cerebral cortex.

It's made of gray matter, so it's where we find the cell bodies, the nuclei, the cell bodies of the neurons. The cerebral nadala on the other hand is the white matter. So this is the white matter inside the brain, we've got lots of white matter and it's white because of the myelinated axons. So we've kind of already covered a lot of this. The corpus callosum is the only connection between the left and the right sides, that's shown in this cartoon as green.

So this is tracks, remember tracks are bundles of axons, bundles of neurons in the central nervous system.

So the corpus callosum contains commissural tracks, commissural tracks.

These are the only connections between left and right in the brain. The basal ganglia, these are shown in this cartoon here in this slightly darker color. These are little groups of cell bodies, so again gray matter, but found in the white matter, it's pockets of gray matter inside the white matter.

And what's important about the basal ganglia is it's where we produce a lot of our dopamine, our dopamine.

Remember from last week, dopamine was important for initiating movement, but also for reward. We do things because we get a dopamine hit. Dopamine hit means we like it and we tend to do it again.

So dopamine is important for reward.

It helps with initiating movement and it helps with coordinating movement. You can also see in the cartoon here other tracks.

So we looked at the corpus callosum, which is our commissural tracks going from left to right, but we've got in pink here, we've got association tracks.

So this is connections between different parts of the brain, connections between different regions, different functional areas. And then in blue, these are our projection tracks. These are the tracks of the bundles and axons as they then head either down the spinal cord.

If they're motor ones, they're going down. If it's sensory, they're coming up.

So it's our projection tracks projecting around the body. So the cerebro, the biggest part of the brain, gray matter on the outside, white matter on the inside, except for our basal ganglia, and various different tracks connecting different parts of the brain to each other. So we've got these two hemispheres left and right, and each hemisphere can be divided into four lobes. So we've got the frontal lobe, which in this cartoon is shown in a kind of orange.

The parietal lobe is shown in yellow, the temporal lobe shown in green, and the occipital lobe shown in blue.

Now they're called the frontal, the parietal, the temporal and the occipital because of the bones of the skull. They're named after the bones that sit directly on top of them. So we have our frontal bone, our parietal bone, our temporal bone, and our occipital bone.

So the lobes are named after the skull bones. And each of these lobes have specialized functions.

So for example, the frontal lobe has a strip just before where the frontal and the parietal lobe meet. That groove there is known as the central sulcus. So it's a groove that sits across the top of the head here, just in front of that groove in the frontal lobe.

This is where we have our motor cortex, our motor cortex.

This is where we control voluntary movement.

So shown in bright orange in this cartoon, this strip that goes across the top of the head, that area controls voluntary movement. In the parietal lobe, we have what's called the somatosensory cortex. So this is a strip shown in the dark yellow here, just the other side of that central sulcus, running across the top of the head here. And this is where our body, our brain, maps our sensation.

So our sensation of our finger is going to go up to the brain and it maps onto that somatosensory cortex and says that's a finger. If the sensation comes from a toe, it maps it to a different part of that strip and says that's where your toe sends messages from. As well as general sensation, we also have within there deep inside there, we have a taste area, which is where we detect consensus different tastes. In the temporal lobe, shown in green here, we have deeper pockets again for auditory functions, that's hearing, auditory, and then deeper inside still is olfaction, which is smell.

So temporal lobes for hearing and the front, but they send their neurons, they cross over, going to the occipital lobe, and that's where we perceive our vision.

That's where we understand what those action potentials mean. And then all over the brain, we have higher order functions. I'll show you a picture for that where we have things like thinking and memory and learning and so on. So I'd like to focus in on these motor cortex and somatosensory cortex. These are these strips that will run across the tongue of your head. So we've got one strip, which is our motor cortex, and then behind it is our somatosensory cortex. And mapped onto that is the human body. It's where our brain is perceiving, whether we are receiving messages from our fingers, our lips, or our toes.

So let's look at here, this is our somatosensory cortex, and it's depicted, it's what's called a homunculus. So the homunculus, here's our person, mapped on across the brain, and then of course you have the same again on the other side. So ignore the right hand side now, that's motor.

Let's focus on sensory here. So mapped onto our brain, we have a really big area for our face, really big area for our hands and fingers, but not much area. Look, the whole of the back is a tiny area of the brain, not much for the legs, but look how big the feet are, really quite big.

Genitalia, sorry to say, they don't get much, much mapping on the brain, not really a lot, not in comparison to say the lips, or the tongue, or the throat.

So much more sensation to certain areas of the body.

For motor, we can see our motor permunculus here, the motor cortex. Again, muscular control of our face, so our mouths, our tongues, mouths, lips, teeth, facial expressions, loads of mapping onto the brain for that, because we use our faces so much for communication.

Hands have a huge representation on the motor cortex, because we have such fine control of our hands and fingers, but not much for the arms, not much for the back, the legs, the buttocks, the feet have got a good amount of control.

the buttocks, the feet have got a good amount of control. No motor control for genitalia, you have no voluntary control over your genitalia, it's all involuntary. Okay, so for the sensory cortex, the size of the area, how much of the brain patch comes from and represents that part of the body, determines how much sensation you've got, so you can imagine it with what's called two point discrimination. Let's have a go at it together. I'd like you to pinch your fingers together, so you've got hopefully two nails, which are about a centimeter apart, and then touch back to the tip of the finger. Can you feel that there's two points of contact? You can feel two nails, don't change that finger there, but now try it on the back of your hand. Okay, so now feel two points, hard isn't it? Now turn it on the arm, can you feel two points of contact or is it just one point of contact?

Try the shoulder, by now you definitely lost two points of contact. Try your lips, can you feel two points of contact there?

Try your lips, can you feel two points of contact there? Yeah, so lips are super sensitive and we know that because it's got a huge area of representation. Fingertips, we can feel two points of discrimination because it's got a big area.

big area. Our back, our back is rubbish. The distance apart, those two points can get on your shoulders is about five centimetres. Put two fingers on your shoulder but just pop two on there. Can you tell if that's two fingers or one finger?

or one finger? Try different distances apart, move fingers, how far apart do you have to go before you can tell it's two? It's rubbish, isn't it? Come head on your lips or your fingers then you can go down to a millimetre. So this is our sensory cortex, mapping onto from past the brain. The same applies to motor, so the area covered on the surface of the brain, that motor cortex, determines how much motor control you've got.

determines how much motor control you've got. So let's have a look at this one, can you draw your fingers on the table or make lots of noise? Draw your fingers, lots of control, some of you will be nervous, can you draw your toes with as much control? No, okay, so that's because our toes don't have as much representation as our fingers but what happens if in a horrific accident you lose your arms?

accident you lose your arms? What do you think is going to happen to your brain? It's going to change the representation so the area that's represented by hand is a waste of space so it will start to shrink but if you need to learn to write with your toes, to control your face does change, there's some plasticity, plasticity means ability to adapt. Okay so that's our sensory and motor cortex, we've seen this picture before, motor, our motor cortex in that frontal lobe, that strip across the frontal lobe, that's where our cell bodies, our neurons, our cell bodies for the upper motor neurons start so it's in the brain matter of that strip across the brain and it's going to send a message down the primary, not the primary, the upper motor neuron which we know decussates at the medulla, the central nervous system is a tract, synapses in the spinal cord and then synapses with a lower motor neuron which is part of our peripheral nervous system, exits at the front, goes to our neuromuscular junction.

Decussation crosses over left, right, right.

Sensation, we learned earlier three neurons carry sensation starting at the skin, we had our primary sensory neuron coming in at the back of the spinal cord, sometimes it decussates straight away, sometimes it goes up the spinal cord first, then at the medulla it synapses and decussates, going to the thalamus, at the thalamus we get another synapse, going to our somatosensory cortex, the parietal lobe, that strip that goes from left to right, across the brain, lapping where you felt it, did you feel it in your finger and it matched to the toe because it's matched to the toe bit on the autism side, does it go wrong? Most things about the body can go wrong.

So we have to think about what happens when we have injuries, what happens if we injure that part of the brain, will we lose motor or will we lose sensation of the lips on the other side of the body, we lose the sensation for feet, we lose the foot bit, motor, if we have a stroke we lose control of the opposite side of the body but not necessarily all of it, we might maintain it in our feet but we lose it in our arms, we might refine the arms but we lose it in the face. So it depends, if we've got a spinal cord injury, oh so it gets all very complicated doesn't it? So motor cortex and somatosensory cortex, these are the important ones, I think super important but we as humans are able to do much more complicated things, we have higher order areas which coordinate and interpret various mental functions, so for example the frontal lobe is not only responsible for motor, we know it's got motor function but it's also important for things like planning and decision making, so if someone has a head injury to the frontal lobe it can affect their decision making, their ability to plan.

to plan. Broca's area is Broca's on here, Broca's area is for motor speech, where's the motor speech?

Broca's area is for motor speech, where's the motor speech? Motor speech is speech production, now speech is complicated and it can be divided into motor speech, our ability to mechanically, muscally make the sounds and that's different to sensory speech where we can understand the speech, so we have different parts of the brain, Broca's area A is for motor, the ability to make the words, whereas vermic's area B is for understanding sensing speech, so if someone has a stroke that affects Broca's area they're not able to speak but they can understand it perfectly, whereas if someone has a stroke that affects vermic's area they can't understand the speech but they can make noises, they can make words, so it all depends on where in the brain you had either the injury like a whack or a knife or a stroke or whatever. Does that mean you say the words but don't understand what you're saying? It's very hard to work out what people are perceiving until you've had these injuries because how much do we know that they understand and it's yeah but even if you have strengths something can be really frustrating and you can understand it all and you say the words and you think you're saying give me the drugs it hurts and what comes out is cats are pink, it's really frustrating so sometimes brain injuries can be really really frustrating for patients.

Parietal occipital areas, spatial awareness and written words, you might not be able to speak but you can still write, see that's another great one, you cannot make them like that, make those noises but you can still write it all out, that bit still works, it all depends on which bit of the brain has been injured.

So the clinical relevance, damage to the cerebral cortex can cause motor problems, if we've damaged the motor cortex it can cause sensory problems, if there's damage to the sensory cortex it can cause cognitive loss like our ability to pan and to reason and to behave ourselves if we've affected those areas and we can do that through head injuries so things like car accidents, bike accidents, concussions, playing rugby, playing ice hockey, strokes at leaves or crops, subjural hemorrhages and all of those things. I think that's a good place to pause, so next week then we have got the rest of the central nervous system and then you also got the peripheral nervous system and then finishing up we've got our final set for seminar, so if we ease into the seminar it's not the end of the world