The blood-brain barrier is very restrictive, preventing even water and small ions from crossing. However, _______ can pass through the blood-brain barrier by sending a signal that opens up the junction.
A)red blood cells
B)immune system cells
C)platelets
D)complement cells
E)epithelial cells

Question

Quizplus · Accepted Answer

Immune system cells, specifically white blood cells, are able to pass through the blood-brain barrier by sending a signal that triggers the opening of the tight junctions between brain endothelial cells. This allows them to enter the brain and respond to infections or injuries.

The Blood-Brain Barrier Is Very Restrictive, Preventing Even Water and Small