Describe the blood brain barrier (50% of marks). What characteristics does a drug need to effectively penetrate the blood brain barrier? (50% of marks)

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College Answer

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.