2014-02-06 10:08:01 UTC
I’ve studied the effects of medications and toxins on living creatures. A design that impresses me is how our brain is protected from dangerous substances and from bacteria. There is a barrier that keeps our blood separate from our brain cells.
What is remarkable about that?
Over a hundred years ago, researchers noticed that substances introduced into the bloodstream enter every area of the body—except the brain and spinal cord. That fact is astonishing to me, because an immense network of tiny capillary vessels takes blood to every cell in the brain. All brain cells are cleaned, fed, and oxygenated by blood. So, how can our blood be kept separate from our brain cells? For many years it was a mystery.
How does the barrier work?
Microscopic blood vessels are not like plastic tubes that keep what’s inside separate from what’s outside. The walls of blood vessels are made of cells. These cells allow substances and microbes to pass through them and between them. However, the cells making up the blood vessels in our brain are different. They’re tightly connected to each other. These cells and the tight junctions between them are amazing. A vast array of complex mechanisms ensure that some things—such as oxygen, carbon dioxide, and glucose—pass between the bloodstream and the brain in a regulated way. But other compounds, proteins, and cells are kept out. So the blood-brain barrier operates at a molecular level to produce physical, chemical, and electrical barriers. For me, such design simply could not have evolved.