Expert: Dana Krempels, Ph.D. - 5/20/2009

Question
Today in my psych class we discussed the blood brain barrier. We were told the blood is toxic to the brain and this protects from direct contact of blood. When ask if it was the plasma or the RBC the teacher said he didn't know. I am now curious and can't find an answer except when I read on here blood is not toxic to brain but there are harmful chemicals in the blood. So this barrier allows essential nutrients in but filters the chemicals out. I am so confused!! Can you clarify this topic for me? Is blood harmful or things in blood? If so what parts?

Answer
Dear Wilma,

To say that blood is "toxic" to the brain is a gross oversimplification.  There are substances carried by the bloodstream that would harm the brain, but there are so many different things and ways this could happen that it's not even fully known by scientists who study this phenomenon.

It may be a little goofy, but this site is actually not bad for explaining it:

http://faculty.washington.edu/chudler/bbb.html

But you can get a more serious explanation here:

http://www.elp.manchester.ac.uk/pub_projects/2002/MNQJ9PP2/Webpages/bloodbrainba...

Forget what you were told in class about toxicity of blood.  The real function of the blood brain barrier is far more subtle and complex, and is mainly involved with the delicate homeostasis needed for proper brain function.

Hope this helps!

Dana