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

The primary function of the blood-brain barrier is to protect the central nervous system by restricting certain molecules. This specialized barrier is formed by tightly packed endothelial cells in the brain's capillaries, which prevent potentially harmful substances, such as toxins and pathogens, from entering the brain while allowing essential nutrients, like glucose and certain amino acids, to pass through. This selective permeability is crucial for maintaining the homeostasis of the brain's environment, ensuring that it remains stable and functional, as the brain is particularly sensitive to fluctuations in its biochemical composition.

The blood-brain barrier plays a vital role in preserving the delicate balance of ions and neurotransmitters that are necessary for neuronal function. Disruptions in this barrier can lead to various neurological disorders, as harmful substances could affect brain activity and health. This protective feature underscores the importance of the blood-brain barrier in safeguarding the brain against external threats while still permitting the passage of necessary substances for its proper function.