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'White matter' is one of the two main solid components of the central nervous system. The other one is gray matter.

Contents

Structure

Function

Location

Types of astrocytes

Clinical relevance

Notes

External links

Structure

It is composed of myelinated nerve cell processes, or axons, which connect various gray matter areas (the locations of nerve cell bodies) of the brain to each other and carry nerve impulses between neurons.
Cerebral and spinal white matter do not contain dendrites, which can only be found in grey matter along with neural cell bodies and shorter axons.

Function

The white matter is the tissue through which messages pass between different area of gray matter within the nervous system. Using a computer network as an analogy, the gray matter can be thought of as the actual computers themselves whilst the white matter represents the network cables connecting the computers together. The white-matter is white because of the fatty substance (myelin) that surrounds the nerve fibers (axons). This myelin is found in almost all long nerve fibers as the insulation is important for allowing the messages to pass quickly from place to place.
The brain in general (and especially a child's brain) can adapt to white matter damage by finding alternative routes which bypass the damaged areas of white matter and can therefore maintain good connections between the various areas of gray matter.

Location

White matter forms the bulk of the deep parts of the brain and the superficial parts of the spinal cord. Aggregates of grey matter such as the basal ganglia (caudate nucleus, putamen, globus pallidus, subthalamic nucleus, nucleus accumbens) and brain stem nuclei (red nucleus, substantia nigra, cranial nerve nuclei) are spread within the cerebral white matter.
The cerebellum is structured in a similar manner as the cerebrum, with a superficial mantle of cerebellar cortex, deep cerebellar white matter (called the "arbor vitae") and aggregates of grey matter surrounded by deep cerebellar white matter (dentate nucleus, globose nucleus, emboliform nucleus, and fastigial nucleus). The fluid-filled cerebral ventricles (lateral ventricles, third ventricle, cerebral aqueduct, fourth ventricle) are also located deep within the cerebral white matter.and suppl

Types of astrocytes

In 1983, M. C. Raff et al. discovered that tissue samples originating from rat optic nerve contained two morphologically distinct types of astrocytes.

★ So-called "Type 1 astrocytes" had a fibroblast appearance and resided in both grey matter and white matter.

★ "Type 2 astrocytes" has a neuron-like appearance and resided in white matter alone (Sherman, Chris).

Clinical relevance

Multiple Sclerosis is one of the most common disease which affects white matter. In MS lesions, the myelin shield around the axons has been destroyed by inflammation.
Changes in white matter known as amyloid plaques are associated with Alzheimer's disease and other neurodegenerative diseases. White matter injuries ("axonal shearing") may be reversible, while grey matter regeneration is less likely.

Notes

External links

★ White Matter Atlas

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