About. The blood brain barrier (BBB) is a dynamic interface that separates the brain from the circulatory system and protects the central nervous system (CNS) from potentially harmful chemicals while regulating transport of essential molecules and maintaining a stable environment.bout. The blood brain barrier (BBB) is a dynamic interface that separates the brain from the circulatory system and protects the central nervous system (CNS) from potentially harmful chemicals while regulating transport of essential molecules and maintaining a stable environment.