blood-brain barrier (BBB) [AS, blod + bragen + ME, barrere] , an anatomical-physiological feature of the brain thought to consist of walls of capillaries in the central nervous system and surrounding astrocytic glial membranes. The barrier separates the parenchyma of the central nervous system from blood. The blood-brain barrier prevents or slows the passage of some drugs and other chemical compounds, radioactive ions, and disease-causing organisms such as viruses from the blood into the central nervous system.
