Many Medications Introduced into the Bloodstream Cannot Directly Affect the Neurons

Multiple Choice

Many medications introduced into the bloodstream cannot directly affect the neurons of the CNS because

A) oligodendrocytes form a continuous myelin sheath around the axons.
B) the endothelium of CNS capillaries forms a blood-brain barrier.
C) the neurolemma is impermeable to most molecules.
D) ependymal cells restrict the flow of interstitial fluid between the capillaries and the neurons.
E) astrocytes form a capsule around neurons.