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

What is the primary function of the blood-brain barrier?

1. To enhance the effects of psychoactive substances

2. To control the flow of substances to the brain

3. To facilitate the metabolism of substances

4. To absorb nutrients for the brain

The correct answer is: To control the flow of substances to the brain

The primary function of the blood-brain barrier is to control the flow of substances to the brain. This specialized barrier consists of tightly packed cells that line the blood vessels in the brain, preventing harmful substances, pathogens, and toxins from entering the brain while allowing essential nutrients and oxygen to pass through. By regulating the movement of molecules, the blood-brain barrier plays a critical role in maintaining the brain's stable environment, which is crucial for proper neural function. In contrast, some options suggest functions that are not accurate roles of the blood-brain barrier. For example, enhancing the effects of psychoactive substances or facilitating the metabolism of substances does not align with the barrier’s protective role. Additionally, while the brain does require nutrients, the absorption of these nutrients is primarily facilitated by other mechanisms rather than being a direct function of the barrier itself. Thus, controlling the flow of substances is indeed the key role of the blood-brain barrier in ensuring brain protection and health.