National Certified Addiction Counselor, Level 2 (NCAC II) Practice Exam Exam

What is the blood-brain barrier?

1. A series of cells that allows all chemicals to reach the brain

2. A series of cells that prevents certain chemicals from reaching the brain

3. A barrier that stimulates brain activity

4. A protective layer surrounding the spinal cord

The correct answer is: A series of cells that prevents certain chemicals from reaching the brain

The blood-brain barrier is a selective permeable barrier composed of specialized cells that tightly regulate the passage of substances between the bloodstream and the brain. This function is critical as it protects the brain from potentially harmful substances, including toxins, pathogens, and fluctuations in blood chemistry while still allowing essential nutrients to pass through. The barrier is primarily formed by endothelial cells that line the blood vessels in the brain, which are joined by tight junctions that prevent unwanted chemicals from entering the brain's extracellular fluid. This mechanism is essential for maintaining the stable environment necessary for proper neuronal function. In contrast, the other choices do not accurately reflect the nature of the blood-brain barrier. The first option incorrectly suggests that all chemicals can pass freely to the brain, which would compromise brain function and safety. The third choice implies that the barrier plays an active role in stimulating brain activity, which is not its primary role; rather, it primarily serves as a protective barrier. Finally, the last option refers to a protective layer surrounding the spinal cord, which is not related to the blood-brain barrier as the spinal cord is part of the central nervous system but is distinct from the mechanisms involved in the blood-brain barrier itself.