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 astrocytes isolate the CNS by forming a blood-brain barrier.
C)the neurilemma is impermeable to most molecules.
D)ependymal cells restrict the flow of interstitial fluid between the capillaries and the neurons.
E)Schwann cells form a capsule around neurons.

Question

Quizplus · Accepted Answer

The astrocytes form the blood-brain barrier, which is a highly selective semipermeable membrane that separates the circulating blood from the brain extracellular fluid in the CNS. The blood-brain barrier blocks the entry of many substances, including many medications, into the brain tissue. This is important for the protection of the CNS as some chemicals can be harmful to brain cells.

Many Medications Introduced into the Bloodstream Cannot Directly Affect the Neurons