Gray and white matter

in this video I'm going to talk about gray and white matter in the central nervous system which is mostly the brain and the spinal cord there are areas called grey matter grey matter that contain most of the neuron somas so most of the neuron somas in the central nervous system are found in the gray matter and then there are other areas called white matter and in the white matter of the central nervous system is most of the myelinated axons myelinated so axons that are wrapped in myelin myelin ated axons and these are actually kind of funny names for these parts of the central nervous system because they're really not gray or white they're all kind of different tan colors in life but when the tissue has prepared certain ways after being removed from the body it can have a grayish appearance or a more whitish appearance and so these are the names that have stuck for these general areas the gray matter and the white matter now the distribution of gray matter and white matter is a little different between the spinal cord and the brain if we look first at the spinal cord here and here we have a really nice illustration of some different sections of the spinal cord so right over here what these drawings represent are different levels of the spinal cord like if we made little sections of it like if we were cutting a loaf of bread and kind of cut from the top down to the bottom and then we're looking down at these sections from the top so that we're kind of looking down this way at the different sections over here in these drawings and what we see in the spinal cord is that most of the gray matter of the spinal cord is on the inside this kind of H shape for this butterfly shape of gray matter and the white matter of the spinal cord is mostly on the outside all this stuff outside this H shape of gray matter and it's a little hard to see on these drawings so let me just take like this one for example and let me just draw it here just a little bigger so I'll just draw kind of an oval like we're looking down at the top of a section of the spinal cord and on the inside is going to be the great that's going to be in this kind of age shape where this butterfly shape you just draw the back part here and all of this stuff would be gray matter so be lots of neuron somas that would give it a different color from the white matter on the outside let me just draw in a little bit of light weight here on the outside because that's how the spinal cord is set up with most of its myelinated axons forming white matter on the outside except for this little bit here where the the gray matter goes to the very back of the spinal cord now for the brain it's a little different than it is for the spinal cord so let's take a look at the brain and make it a little bigger with this drawing over here and on this drawing we're going to be looking at the brain from the left side let me just write that up here so this is the brain from the left side like we're looking over this way at the brain with the cerebrum on top and the cerebellum back here and then the brainstem we just see a little bit right here and then this drawing is going to be of kind of the inside of the brain like if we kind of cut along the brain kind of like this through a bunch of the cerebrum and the brainstem and we're kind of looking at it from the front so we're looking at it this way after cutting it through here so that we can look at the inside of the brain tissue now where the spinal cord had gray matter mostly on the inside the brain actually has gray matter mostly on the outside so here you can see this layer of gray matter that's going all the way around the outside of the cerebrum here and this layer of gray matter on the outside of most of the brain is called cortex core-tex and this cortex covering the surface of the cerebrum is called the cerebral cortex and the cortex covering the cerebellum down here is called the cerebellar cortex and that's all grey matter on the outside of those parts of the brain that contain most of the neuron somas so I'll just draw some little circles here to represent neuron somas although they're actually much smaller than this if we did it to scale and also kind of the reverse of the spinal cord where most of the white matter was on the outside of the spinal cord most of the white matter of the brain is on the inside so this lighter colored stuff here under the cerebral cortex this is all white matter deep inside the cerebrum and white matter down here in the brainstem now there are some other areas deep in the brain that are gray matter that contain lots of neuron somas like this right here and instead of calling these areas cortex like the gray matter on the outside the gray matter that's kind of deep in the brain we call nuclei one would be a nucleus and multiple as nuclei and there are multiple nuclei deep in the brain these areas of gray matter like here are several right here and here's another one right over here now in the white matter of the central nervous system are collections of axons that are traveling together to different areas I'll just draw a dashed line to show that these axons are going to keep going but there are multiple neuron axons that are kind of traveling together they're starting in a similar area and they're heading to a similar area somewhere else in the central nervous system and collections of axons traveling together in the central nervous system we call tracts tracts so this would be one tract right here and a tract could have many many axons in it carrying often a very similar kind of information from one part of the central nervous system to another part of the central nervous system the central nervous system has a huge number of neurons and at doing lots of different functions in addition to neurons involved in motor sensory and automatic functions like we talked about with the peripheral nervous system the central nervous system it also has lots of neurons participating in the higher functions of the nervous system that is participating in cognition emotion and consciousness and that's particularly in the cerebral cortex all this gray matter on the outside of the cerebrum and certain other parts of the brain are very involved in those higher functions of the nervous system as well