字幕表 動画を再生する 英語字幕をプリント Okay, so this is a tutorial on the parts of the brain. So, this is a basic tutorial and I want to give you an overview of the different parts that make up the brain. So there's not going to be huge amounts of detail here, but this is just a tutorial to sort of orientate yourself with regard to structures of the brain. So we'll start off by looking at the brain stem. So, first of all, I'll just point out what we're looking at here. We're looking at a side view of the brain. Anterior is this side, posterior is this side, and obviously superior and inferior. So, you can sort of see the veins and how it sits there. So I'm just going to rotate it around and we'll take a look at the brain stem. So I've just removed some of the nerves to make it a bit more clearer. So, the brain stem is this bit here and it consists of three parts. You've got the medulla oblongata, the pons, and the midbrain. So the medulla oblongata is this bit here, which is most distal or most inferior, and it starts at the end of the pons and it ends where the spinal cord begins. So the spinal cord begins at the opening of the skull at the foramen magnum, and this is where the medulla oblongata ends. So, just above it you've got the pons, which is this bit here. And above the pons, you've got the midbrain. So, what I'm going to do is just isolate the brain stem. So I've just removed all the other structures. We're looking at the exact same view. You've got the medulla at the bottom; the pons and the midbrain above it. So the midbrain is this region here and it consists of -- so, at the front, you've got these bits, which are called cerebral peduncles and, at the back, you've got these little sort of hills, and these are called the corpora quadrigemina, and this is Latin for quadruplet bodies because obviously there's four little bumps. So, the top ones are called superior colliculi and the bottom two are called inferior colliculi. And the word colliculi is Latin for lower hills, because of their appearance. So, these colliculi sit on the tectum, so the tectum is sort of the roof of the midbrain. So, tectum means roof in Latin, so here corpora quadrigemina sit on the tectum of the midbrain. So the midbrain is this structure here. You've got the cerebral peduncles and you've got the tectum with the four colliculi. So, in the midbrain, you've got loads of nuclei. So, nuclei are collections of cell bodies, which are contained in the nervous system. Sorry, in the central nervous system, whereas ganglia are collections of cell bodies in the peripheral nervous system. So, in the brain stem, there's lots of nuclei, which are important for controlling functions like heart rate and blood pressure and respiration as well as things like the level of consciousness and wakefulness and arousal. And then you've got lots of cranial nerve nuclei and nuclei related to the cerebellum, which I'm just about to show you. So I've just switch back to this model and I'll just show the cerebellum. So, the cerebellum is this part of the brain, which sits behind the brain stem. So you can see it here, sitting directly behind the brain stem, and you can see it has these two lobes. So the cerebellum means little brain in Latin, and this has loads of connections with the brain stem and it's important in motor control and coordination and balance and muscle tone, and that sort of thing. So, if I remove the cerebellum, and I'll just remove the hemispheres as well. So, we can see the midbrain here, so you can identify them by the colliculi. So that's the midbrain sitting. Well, this is the dorsal surface of the brain stem. So, the next part of the brain that we need to talk about is called the diencephalon, and this is the part of the brain that sits on top of the midbrain and it consists of the thalamus, the hypothalamus, and the pineal body or the pineal gland, which is what it's also called. So, I've just removed the cerebral hemispheres and the cerebellum, and we're looking at the back of the brain stem. So, remember, you can see the midbrain here, which is easy to notice, and then, below, you've got the pons and the medulla oblongata. So the midbrain is sitting just above this. So, you can see this paired structure. These paired sort of oval roundish structures. These are called the thalami, and you've got two thalami. So, one on each side, and they're joined at the middle via the interthalamic adhesion. So, just below the thalamus you've got the hypothalamus, which is a little bit smaller. So the hypothalamus sits here. So I just got rid of a few of these structures so you could see the oval-shaped thalamus and the hypothalamus below it. And at the back, just here, you've got the pineal gland. So the thalamus is a really important structure to know about because it essentially acts as a switchboard or gateway to the cerebral hemisphere, so it relays connections to the cerebral hemisphere - to the cerebral cortex of the cerebral hemispheres. And it contains lots of nuclei. So, the thalamus sends and receives fibers from the cortex and it's got thalamo-cortical loops and lots of reciprocal connections. So, it's important for many things such as sleep and wakefulness. It's important in coordinating information from the various sensory systems and it also has links to the basal ganglia, which I'll come to talk about, and also the cerebellum. So, I've just switched to this lateral view. I've removed various structures so you can visualize the thalamus right in the center very clearly. So you get a lot of fibers projecting into the thalamus and the thalamus coordinates all this information and it projects fibers into the cortex and it also receives fibers back from the cortex. So you'll often hear the thalamus referred to as a relay or switchboard or a gateway for this reason. So, the cerebral hemispheres are what most people think of when they think of the brain. So, we're looking at these two cerebral hemispheres here. You've got a right and a left cerebral hemisphere. And the cerebral hemisphere is responsible for higher functions. So, thinking, memory, consciousness, language, emotion, movement, and sensory perception - these kinds of things. So, the cerebral hemisphere consists of an outer cortex, which is made up of six layers of gray matter, and you've got the inner portion of the cerebral hemisphere, which is made up of white matter. So, I'm just going to rotate the brain around and I'm going to switch to a diagram to illustrate the cerebral cortex. So if we take a...so imagine just cutting the brain through this axis here. So, directly -- we're going to take a slice of the brain down here. So we're looking at this cross section of the slice we've just taken, so this is a coronal section. And what I wanted to show you on this slice is the cerebral cortex. So, the cortex is the outer part of the cerebrum and it is gray matter. So, you can see this thin bit on the edge of the cerebrum. This is the cerebral cortex and it consists of up to six layers of neural tissue. So, the neocortex is where the cortex has six layers. Any other parts with less than six layers is referred to as the allocortex. And this allocortex can be subdivided into an archicortex and a paleocortex, so these are part of the cortex with less than six layers. The neocortex is the one to remember because this is the newer, sort of evolutionarily newer, part of the cortex and is responsible for higher functions like language and conscious thought. So the neocortex has six layers. So, just looking at the outside of the cerebral hemisphere, you can see that there are these grooves and you've got ridges. So the ridges are called gyri and the grooves are called sulci. And you've got lots of these different grooves and ridges, as you can see, and they all have different names. But two important ones to remember are the central sulcus, which I'm showing you here with the arrow, and the lateral sulcus. And I'll do another tutorial, which goes through all these different grooves and ridges. But the reason I showed you these - the two sulci, the central sulcus and the lateral sulcus - is because these two sulci can be used to separate some functionally important lobes of the brain. So you've got four lobes of the brain, which are separated by various grooves. So, anterior to the central sulcus, which I'm drawing along here, you've got the frontal lobe because it sits behind the frontal bone of the skull. So, this is the frontal lobe that I've outlined in red. Posterior to the central sulcus, you've got the parietal lobe, and this runs like this, so I'm outlining this in yellow. And this is called the parietal lobe because it lies under the parietal bone. And inferior to the lateral sulcus, which I'm drawing on in green, we've got the temporal lobe. So I'm just outlining the temporal lobe here, and it runs like that. And right at the back we've got this lobe here, called the occipital lobe, which I've just outlined in blue. So this is quite a rough illustration of the four lobes, but I wanted to show you how the central sulcus and the lateral sulcus are important and defining these different areas. So, anterior to the central sulcus, you've got the front lobe; posterior to it, you've got the parietal lobe. And then you've got the lateral sulcus, which, inferior to the lateral sulcus, you've got the temporal lobe. So the frontal lobe is important in decision making, problem solving, and planning. The temporal lobe is important in memory, language, emotion, and hearing. And the parietal lobe acts as sort of integrator of sensory information, so it receives and processes sensory information and the occipital lobe, sitting at the back, is responsible for vision. So, that's a very crude overview of their functions, but it gives you an idea that different lobes have different functions.