Answer: Tight junctions between brain capillary endothelial cells (and astrocytes).
- A Neurons themselves, by forming an insulating layer around capillaries
- B Tight junctions between brain capillary endothelial cells (and astrocytes)
- C The bony skull enclosing and protecting the brain
- D Cerebrospinal fluid alone, cushioning the brain tissue
Correct answer: B. Tight junctions between brain capillary endothelial cells (and astrocytes)
Explanation: BBB: tight junctions between brain capillary endothelial cells (reinforced by astrocyte end-feet) restrict passage of most substances from blood to brain.
Structure of a neuron. Image: LadyofHats (Mariana Ruiz), Public Domain, via Wikimedia Commons.
Concept context
Brain, spinal cord, neurons, reflex arcs, and sense organs.