What is the Blood-Brain Barrier?

Our bodies are wonderful machines. They do and accomplish literally billions of activities that day and almost all of these activities come off with 100% accuracy almost every single time. Through millions of years of evolution — which is basically nature’s way of engaging in trial and error experimentation on a grand scale — our bodies have learned what works and what does not. Because of this experimentation there are mechanisms within our body that keep us safe from harm, both outside our bodies and from within our bodies.

One such mechanism is what scientists and health professionals refer to as the “blood/brain barrier.” This type of figurative wall acts as a kind of gatekeeper that prevents harmful chemicals or even minor changes in the blood’s chemistry and pH balance from overly affecting the brain through a mechanism that has proven to be highly resistant to certain water-soluble chemicals that could make their way into the brain and the fluid surrounding it and which would lead to ultimate physical harm.

Such chemicals or substances are fairly well known, including heavy metals such as mercury. This kind of exposure to mercury can lead to a wide range of neurological deficit disorders when the metal makes it through the blood/brain barrier due to weakness of the barrier or dysfunction which has created the conditions where heavy metals, chemicals or changes in blood and fluid pH are present. Evolutionary processes work to keep the brain pH levels tightly controlled as possible while also working to prevent any exposure of the brain to toxic agents.

As a physical entity, the blood/brain barrier is comprised of a vast array of what are called “end brain capillaries,” each of which benefit from a seamless and of very tightly knitted junctions that are enclosed even more tightly by a type of connective tissue. Working together, these networks form a highly restrictive barrier, for all intents and purposes that act to prevent the brain from being affected by even very minor changes in pH and other agents having what are called “high molecular weight.”

The barrier has been so completely evolved that it is able to allow fat-soluble, lighter weight substances, for the most part, to pass through. Very specific water-soluble amino acids are also allowed to pass through this barrier to facilitate certain other neurochemical reactions and that is about all that is allowed to make the journey when the blood/brain barrier is working in good order. That is also why — unless the exposure to the heavy metal is very large — this barrier can work to shuttle outward any mercury that has managed to make its way up to the barrier itself.

As an adjunct part of the classic blood/brain barrier, another part of the body — called the choroid plexus — works in a similar manner to restrict the flow between blood vessels like capillaries and the body’s cerebral spinal fluid (CSF). This serves a dual purpose of not only protecting precious cerebral spinal fluid from harm but also works in conjunction to add just a bit more protection for the body’s most precious organism, the brain.

For the layman, it might be helpful to think of a series of increasingly robust filters through which contaminated water must pass. At the end of that filtration cycle pure, fresh water emerges. These filters, the openings — or pores — which become increasingly smaller as the filters get closer to the tap or outlet where the final product will emerge would be self repairing and constantly replenished in a system that resembles how the body utilizes its own blood/brain barrier.

Clinicians and physicians have certain tools and tests available to them to assess whether or not the barrier is functioning at optimal levels. They usually employ these tests when a person begins to demonstrate what they call “neurological deficit.” They will examine the presence or non-presence of certain proteins or normally benign chemicals that will give a specialist in idea of how well the blood/brain barrier is working at that particular moment in time.