Defending the Fortress
Molecules in the bloodstream pass through the circulatory system directly into the brain via the Blood Brain Barrier (BBB). The BBB is a highly selective network of specialized capillaries, astrocytes and microglia. It functions to keep out destructive substances and mounts the first response aimed at destroying invaders. There are three layers of the BBB. Layer one is composed of capillaries and lets only the smallest substances pass in and out of the brain. Astrocytes comprise layer two. Astrocytic projections or “feet” wrap around the capillaries and strengthen the barrier. They respond to unknown substances with a massive release of inflammatory cytokines that attack the substances and call forth other microglia. The microglia are the third layer of the BBB. They attack anything suspicious with a pinpoint barrage of inflammatory chemicals aimed at destroying the substances.
Look at the graphic on page 31 of the Neuroplastic Transformation workbook. It shows a capillary in the brain running through an astrocyte. Every nerve cell, capillary, microglial cell and oligodendrocyte are contained within astrocytes. Look at the graphic on page 30 of the workbook.