BRAIN – 1
WHITE MATTER AND GRAY MATTER
The upper figure is a schematic drawing of the brain and cerebellum, organs that will be analyzed on the following pages.
In the central nervous system, there are regions with a high concentration of neuronal cell bodies and regions with a high concentration of neuronal extensions, mainly axons but also dendrites.
When a recently removed fresh brain or cerebellum is observed macroscopically, these two regions can be identified.
The regions with a high concentration of neuronal cell bodies have a grayish color, and are therefore called the gray matter of the central nervous system.
On the other hand, the regions with a large number of neuronal extensions have a large amount of myelinated nerve fibers and for this reason have a whitish color. They constitute the white matter of the central nervous system.
While gray matter is the site of reception and integration of information and responses, white matter constitutes the communication pathways between different regions of the central nervous system.
The lower figure
Site of white and gray matter in the brain:
Gray matter is present mainly in two places:
– at the periphery of the organ, just below its surface, forming the cerebral cortex;
– inside the brain and cerebellum, in clusters of different sizes formed by a high concentration of neuron cell bodies called brain or cerebellar nuclei.
White matter occupies the interior of the brain, below the cortex and around the nuclei.
The lower figure shows a cross-section of the brain and, in a simplified way, the distribution of gray matter – in the cortex and brain nuclei – and the white matter.
