Inside the Closed World of the Brain: How brain cells connect, share and disengage--and why this holds the key to Alzheimer's disease by Margaret T Reece

Author:Margaret T Reece [Reece, Margaret T]
Language: eng
Format: epub
Publisher: Reece Biomedical Consulting LLC
Published: 2015-06-15T23:00:00+00:00

ADULT GLIA AND MICROGLIA

ASTROCYTES

Astrocyte glia comprises the most abundant cell population in the adult brain and spinal cord. Astrocytes outnumber neurons by over fivefold. No region of the brain lacks astrocytes (Figure 6-2).

Figure 6-2: Protoplasmic astrocytes in the human cerebral cortex stained with Cajal’s gold sublime method. Photomicrograph: ©Jose Luis Calvo

Astrocytes tile the brain in an ordered non-overlapping arrangement. Individual astrocytes manage distinct domains. Only the most distal tips of membrane extensions radiating from individual astrocyte cell bodies touch one another. Each astrocyte exhibits 5-10 main radiating extensions that give rise to numerous finer branches.

Astrocytes divide into two main subtypes, protoplasmic and fibrous, based upon their morphology and anatomic location in the brain. Protoplasmic astrocytes spread in the gray matter near neuron bodies. Fibrous astrocytes (Figure 6-3) position themselves throughout all white matter where they make contact with axons at Nodes of Ranvier.

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