C_S_D 4430 Lecture 41: L41
Document Summary
Neurons require a bath of consistent ionic composition, they are much less tolerant of changes than are other cells. The barrier isolates the brain form fluctuations in blood chemistry to maintain a stable, well-regulated chemical environment. Substances that circulate in the blood in fluctuating concentrations are excluded from the brain, and those that are needed are allowed in through special transport mechanisms. The bbb is an extensive interface between the brain and circulatory system. Where brain cells come into contact with blood vessels (capillaries) adjacent cell surfaces are in such close contact that no space exists between them = forming a tight junction . The tight junction serves as a hydrophobic barrier that passes only fat- soluble, non-polar (non-charged) molecules. There are special pumps that take up needed polar (charged) molecules such as amino acids and glucose. While the bbb serves to protect the brain from harmful chemicals, it also serves as a barrier to helpful medications.
