What Is Cerebral White Matter?

Sandra Koehler

The main hub of the central nervous system — responsible for receiving, interpreting, and delivering information entering the body — is the brain. Though the brain is complex, with multiple divisions called lobes that are responsible for different actions and reactions, it is basically divided into two main tissue types: cerebral white matter and gray matter. White matter, the bulk of the deepest sections of the brain, is responsible for the delivery of messages through the gray in order for these signals to be transported to the appropriate part of the body.

Lipid tissue that makes up white matter gives it its white appearance.
Lipid tissue that makes up white matter gives it its white appearance.

Made up of parcels of myelinated axons or nerve cells, the white matter processes and transports both chemical and electrical signals so the body can react to internal and external stimuli or changes. Myelinated axons are projections of a neuron insulated with a myelin sheath or covering. The myelin sheath is an electrically charged casing capable increasing the transmission speed of incoming stimuli. These protected neurons steer electrical impulses away from the soma or cell body, the spherical part of a nerve cell where incoming information is sorted. This is the main pathway to distribute data to the rest of the body.

The axons that carry nerve impulses are protected by a myelin sheath.
The axons that carry nerve impulses are protected by a myelin sheath.

Cerebral white matter appears whitish because it is also made up of lipid tissue. Lipid tissue is a collection of molecules such as fat, some types of steroids, vitamins, and fatty acid chains. This tissue is an important feature of white matter, as it gives it the ability to receive and transmit information while protecting the nerve cell from harm. Inside this lipid tissue of cerebral white matter are small blood vessels called capillaries whose function is to supply nutrients such as oxygen, and to remove wastes such as carbon dioxide.

The myelin insulated nerve cells of cerebral white matter allow information to be distributed to the appropriate part of the body quickly. This method of prompt processing of information gathered by the brain allows the body to instantaneously react to changing circumstances. This process also allows the body to maintain homeostasis, the body’s internal stability.

Within the brain there are three different types of cerebral white matter. The projection tract sends messages from the cortex to other parts of the brain or to the different muscles of the body. The commissural tract sends information between the right and left hemispheres or sides of the brain. The association tract transmits information between different sections or lobes of the brain on the same side. This complex system gives the brain the ability to process and react immediately.

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