12. The Central Nervous System

Introduction to the Central Nervous System

Anatomy & Physiology

12. The Central Nervous System

Introduction to the Central Nervous System

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Hey, everyone. So, in this video, we're going to be talking about white matter and gray matter. The nervous tissue that makes up the brain and spinal cord is comprised of two types of matter. We have our white matter, which is made mostly of myelinated axons. The presence of all that fatty myelin gives them an actual white appearance, so they actually look white. And then our gray matter is kind of everything else. This includes our neuron cell bodies, our dendrites, and any nonmyelinated axons. These tend to have a tannish gray appearance, which is where we get the term gray matter from.

Now, white matter and gray matter aren't just dispersed throughout the brain and spinal cord all willy-nilly. They follow a very distinctive pattern. In the brain, we have an outer layer of gray matter called the cortex. This is the literal outer layer. This is the part of the brain that you can see. It has that kind of wrinkly appearance to it. We have this outer layer of gray matter, and then we have an inner layer of white matter. In the brain, we also have these subcortical, literally under the cortex, little clusters of gray matter called basal nuclei. If you look down at our brain over here on the left, you can see all the way around the edge, and it goes all the way around covering the entire surface of the brain with our cortical gray matter. Then you can see this inner layer of white matter, that kind of lighter pink color in our image. In the white matter, we have these little pockets or clusters of gray matter, those are our basal nuclei. We have our white matter on the inside there.

That is how they are laid out in the brain. What we see in the spinal cord actually has an opposite pattern. So, if we scooch over let me scooch down so you can see that spinal cord better. Here we're looking at a cross-section of the spinal cord over here on the right, and you can see the outer layer is now white matter and it has this inner layer of gray matter. We see an opposite pattern where the spinal cord has outer white matter and inner gray matter, and the brain has an outer layer of gray matter and an inner layer of white matter with some little subcortical clusters of gray matter.

That is white matter and gray matter in a nutshell, and I will see you guys in our next video. Bye-bye.

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a. What does lateralization of cortical functioning mean? b. Why is the term cerebral dominance a misnomer?

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