ELI5- How does the blood brain barrier work? Specifically what happens at the crossover?

1.20K views
0

ELI5- How does the blood brain barrier work? Specifically what happens at the crossover?

In: Biology

Blood vessels are leaky. Things can move in and out. This includes hormones and drugs and whatnot. The brain doesn’t want all this, so there are cells called [astrocytes](https://ai2-s2-public.s3.amazonaws.com/figures/2017-08-08/0c5adac783f4d2acd49ee5fd1616d9de26a092a7/5-Figure1-1.png) that encircle all the blood vessels in your brain. They make a big wall around the blood vessels. Then they get to decide what comes in and out. This just adds another layer of control for what can go into the brain.

In normal blood vessels, the wall of the vessel is made of cells, but it contains periodic holes that allow larger molecules like proteins and even entire cells to move through into the extracellular fluid. The BBB has much tighter seals between cells and doesn’t possess these holes, so the only molecules that can move through are those small and polar-enough to do so by passive diffusion (moving straight through the cell membrane) and those that the BBB cells specifically want to move through – they have proteins called channels in their membranes that can pick up key molecules like glucose and pull them in.