glial cells One of the types of cells composing the brain that protect, support and feed neurons, outnumbering them 10 to one—the brain contains more than 100 trillion glial cells. Some of the glial cells seem to act as a sort of bed for neurons. unlike neurons, glial cells do not generate electrical impulses, but they do play an important supportive role in maintaining efficiency along the brain's nerve network. They help to form a covering to protect the large neurons in the spinal cord; myelin is placed around the axons of some neurons by a particular type of glial cell, and axons covered by this myelin sheath conduct impulses up to 12 times faster than those without it. The areas of the brain that contain myelin-covered axons are called the white matter because the myelinated axons look white. In addition, some glial cells may get rid of dead neurons.
glioblastoma A fast-growing, highly malignant type of brain tumor. Glioblastoma multiforme is a type of glioma, a tumor arising from the glial cells within the brain. Most glioblastomas develop within the cerebrum (the main mass of the brain). This type of brain tumor occurs in 10 out of a million people in the United States each year.
The most common primary brain tumor of adults and the third most common of preteens, it occurs most often in those between ages 48 and 60, affecting twice as many men as women and whites more often than non-whites.
It is a rapidly spreading tumor with tentacles that invade nearby tissue, resembling a butterfly pattern of distribution throughout the white matter of both cerebral hemispheres. The spread of this tumor outside the brain and spinal cord is rare.
While glioblastomas may occur in any part of the cerebral hemispheres, they are most common in the FRONTAL, TEMPORAL, and PARIETAL LOBES.
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