Certified Brain Injury Specialist Practice Exam

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

1. Facilitate the flow of nutrients into the brain

2. Prevent harmful substances from entering the brain

3. Enhance the immune response in the brain

4. Support synaptic transmission

The correct answer is: Prevent harmful substances from entering the brain

The primary function of the blood-brain barrier is to prevent harmful substances from entering the brain. This selective permeability is crucial for maintaining the brain's homeostasis and protecting it from pathogens, toxins, and various chemicals that could interfere with neural function. The blood-brain barrier is composed of tightly packed endothelial cells in the brain’s capillaries, which significantly restricts the passage of substances, allowing only certain molecules, like oxygen and glucose, to cross freely while blocking larger or potentially harmful compounds. The importance of this barrier lies in its role in safeguarding the delicate neural tissue from fluctuations in the bloodstream and maintaining a stable environment necessary for optimal brain function. By effectively regulating what can enter the brain, the blood-brain barrier plays a vital part in preventing inflammation and maintaining the integrity of neural circuits.