White Matter vs. Gray Matter: Difference & Medical Terms

White Matter vs. Gray Matter: Difference & Medical Terms
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  • 0:01 White Matter & Gray Matter
  • 0:40 Why the Color Difference?
  • 1:54 Location and Function
  • 2:57 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov
This lesson will define white matter vs. gray matter, explain why a color difference exists, and go over where each is found in the brain and spinal cord as well as their functions.

White Matter and Gray Matter

White matter vs. gray matter, what does it matter? What's the big difference between these two? Where can we find them? And, why the color difference? Well, you'll learn about that right now. Firstly, let's define white matter vs. gray matter.

White matter is the whitish nerve tissue of the central nervous system that is mainly composed of myelinated nerve fibers (or axons). The central nervous system is the brain and spinal cord. And gray matter is grayish nerve tissue of the central nervous system mainly composed of nerve cell bodies and dendrites.

Why the Color Difference?

To help understand this color difference and the term unmyelinated or myelinated, let's turn to a common household object. Imagine you have a white wire or cable in front of you. Commonly, the wire itself is made up of internal 'naked' fibers that are of a silvery gray color. One reason for why the wire fibers are encased in this white insulation is because it helps the wire conduct signals better.

Well, neurons (nerve cells) have these wire like structures that come off them called axons, which carry a signal from a nerve cell body. If a neuron's axon is myelinated, or that is to say, encased in a protective covering called a myelin sheath, it gives off a whitish color. A whitish myelin casing helps nerve cells conduct signals better and faster. However, a neuron's cell body and its tree-like projections (the dendrites) are not myelinated, they're sort of naked like the grayish wire fibers, and they give off a gray color as a result.

Locations and Function

Depending on whether we are in the brain or spinal cord, the white and gray matter are found in generally different locations. In the brain, the gray matter makes up the cerebral cortex, the superficial portion of the brain, as well as some internal structures, while the white matter sits internally, that is to say deeper, to it. This is the opposite of the spinal cord, where the white matter sits externally, or superficially, to the gray matter.

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