Discuss the blood-brain barrier and how it protects the brain. The BBB restricts the entry to the brain of some blood-borne substances while allowing others to enter. You should discuss how the structure of the BBB prevents the entry of some molecules but allows others through. You should discuss why this discrimination is necessary. You could discuss the entry of drugs, both those used as medicines and those sold illegally. You may choose to discuss the BBB in newborn babies, or how it makes the treatment of some neurological disorders difficult, or how the CSF is made and differs from the blood. You could describe the blood supply to the brain. Please mention your source.