The blood-brain barrier:
A)Is a valve-like structure that prevents the peripheral blood from mixing with the cerebrospinal fluid
B)Is formed by pores in the blood vessel walls that control which molecules can pass through
C)Does not allow lipid soluble drugs to enter the brain
D)Requires special transporters to move amino acids and vitamins into the brain

Question

Quizplus · Accepted Answer

The blood-brain barrier (BBB) is a highly selective permeability barrier that separates the circulating blood from the brain and extracellular fluid in the central nervous system (CNS). It does not function as a valve (A is incorrect) nor is it formed by pores in blood vessel walls (B is incorrect). Instead, it consists of tight junctions between endothelial cells in CNS capillaries. Lipid-soluble drugs can actually cross the BBB more easily due to their ability to dissolve in the cell membrane (C is incorrect). Special transporters are indeed required to move amino acids and certain vitamins across the BBB, as it restricts the passage of most substances to protect the brain (D is correct).

The Blood-Brain Barrier