Describe the blood brain barrier (50% of marks). What characteristics does a drug need to effectively penetrate the blood brain barrier? (50% of marks)
The BBB is the separation of the blood from the brain extracellular fluid and serves to
maintain consistent internal environment in the brain and protect the brain from large
harmful substances and microorganisms. Most answers displayed some knowledge of the
structure of the BBB but many answers did not include its function. Better answers included
substances to which the BBB is permeable, how permeability changes with age and a
mention of the circumventricular organs and their significance (i.e. are outside the BBB).
Most candidates correctly identified the characteristics of drugs that cross the BBB. Marks
were also allocated for giving examples.