Question

Which of the following is NOT a true statement regarding the blood-brain barrier (BBB)? O it prevents passage of possible therapeutic drugs it prevents the flow of proteins across it O it allows easy passage of lipid-soluble substances O it consists mainly of gap junctions astrocytes play a primary role

Answer 1

The incorrect statement about the blood-brain barrier is that it 'consists mainly of gap junctions,' as it consists of tight junctions. The BBB restricts entry to the CNS, affecting drug delivery and protection against substances.

Step-by-step explanation:

The blood-brain barrier (BBB) is a selective permeability barrier that regulates what substances can enter the central nervous system (CNS) from the blood. Of the statements provided, the one that is NOT true regarding the BBB is that 'it consists mainly of gap junctions'. The BBB consists of tight junctions that form a barrier to prevent most substances, particularly hydrophilic substances, from entering the CNS. However, it does allow certain substances, like glucose, amino acids, and lipid-soluble molecules, to pass. Furthermore, the BBB can be problematic for drug delivery because it can prevent the passage of potential therapeutic drugs. Astrocytes contribute significantly to the BBB as they release factors that promote the tightness of the capillary endothelial junctions and their end feet surround the blood vessels, contributing to the barrier's structure and function.

Answer 2

The incorrect statement about the blood-brain barrier is that it consists mainly of gap junctions. In reality, the BBB is formed by tightly joined capillary endothelial cells, supported by astrocytes, and it regulates the entry of substances into the CNS.

Step-by-step explanation:

The blood-brain barrier (BBB) is a highly selective semipermeable border that separates the circulating blood from the brain and extracellular fluid in the central nervous system (CNS).

The statement that is NOT true regarding the BBB is that "it consists mainly of gap junctions". Instead, the BBB is formed by capillary endothelial cells that are connected by tight junctions, not gap junctions, which create a barrier to most substances.

Astrocytes reinforce this barrier by sending out end feet that surround the endothelial cells of the BBB, thus playing a primary role in its maintenance. The BBB does prevent the passage of certain therapeutic drugs and the flow of proteins across it.