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Anna, Teacher, writer, biologist
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Why is the blood brain barrier considered both good and ba

Resolved Question:

Why is the blood brain barrier considered both good and bad?
Submitted: 5 years ago.
Category: General
Expert:  Anna replied 5 years ago.

The blood brain barrier consists of miles of tiny capillaries throughout the brain, which are packed with endothelial cells that are selective in what gets through to the brain. With only a few exceptions, this allows only small molecules that are fat-soluble to pass through. Caffeine, nicotine, and alcohol are a few of these molecules.

The blood brain barrier is good in that it protects the brain from many chemicals that would be harmful to it. It also maintains a constant chemical state for the brain, allowing it to function better. Some chemicals which are beneficial in cases of certain illnesses can harm the brain, and the blood brain barrier prevents that. For example, in many collie dogs, there is a genetic defect which allows the penetration of chemicals that are not allowed in normal circumstances. In these dogs, treatment with certain anti-parasitic medications, anti-diarrheals, and cancer chemotherapy drugs can be fatal because the blood brain barrier allows them to penetrate, causing neurological damage.

The blood brain barrier can be bad when a certain drug would benefit a person if it could reach the brain, but the blood brain barrier doesn't permit that. For example, there are promising treatments for certain mental illnesses, including bipolar disorder and certain types of depression, but the large-moleculed drugs cannot penetrate the blood brain barrier. Scientists are working on genetically engineered versions, encased in liposomes that may be able to pass through, but so far, they are not available.

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