The blood-brain barrier (BBB) makes it hard to understand how the central nervous system (CNS) works. Here are some key points:

1. Selective Permeability:

   • The BBB only allows certain medicines to enter, making it tough to treat brain diseases.
   • This is a big problem when trying to get effective drugs to the brain.

2. Tight Junctions:

   • Cells in the BBB bond tightly together, which limits how nutrients can get through.
   • This can cause a lack of important nutrients in brain diseases, making them worse.

3. Immune Privilege:

   • The BBB stops the immune system from working well in the brain.
   • This makes it hard to fight off infections and leaves the brain open to harmful germs.
   • Autoimmune problems can get worse because the immune system isn’t able to watch out for issues as it should.

Possible Solutions:

• Creating special carriers to help medicines cross the BBB better.
• Looking into new methods (like using ultrasound or focused drug delivery) that might improve treatments for the brain.
• Learning more about how the BBB works so we can send treatments directly where they are needed.