This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
[{'content': 'Which of the following is referred to as either physical barriers or physiologic processes (transport system) that separate the circulating blood from the brain extracellular fluid in the central nervous system (CNS)? \nSelect and explain. \nA. Circle of Willis, B. Blood-brain barrier, C. Corticobulbar projections, D. Lateral corticospinal tract', 'role': 'user'}, {'content': 'Answer: B \nExplanation: B:\xa0Blood-brain barrier\xa0serves to restrict and control the movement of substances between the general circulation and brain\xa0extracellular\xa0fluid.\nA:\xa0The Circle of Willis\xa0is an arterial polygon formed as the internal carotid and vertebral systems anastomose around the optic chiasm or chiasma (partial crossing of the optic nerve). It provides blood to the brain and neighboring structures.\nC:\xa0Corticobulbar projections\xa0have several functions including voluntary control over cranial nerves, relay to the cerebellum, activation of other descending pathways and modulation of sensory processing.\nD:\xa0Lateral corticospinal tract\xa0is responsible for controlling the speed and precision of skilled movements of the hands.', 'role': 'assistant'}]