Final answer:
Pericytes are not microglia and do not contribute to the blood-brain barrier; this statement is false. It is astrocytes that play a key role in the formation of the blood-brain barrier by regulating substances that enter the brain from the bloodstream.
Step-by-step explanation:
The statement 'Pericytes are microglia that contribute to the blood-brain barrier' is false. Pericytes are not microglia; they are distinct cells with their own role in the blood-brain system. Microglia are the brain's resident immune cells, which protect the central nervous system (CNS) from infection and are involved in the degradation of dead cells. On the other hand, it is the astrocytes that are closely associated with the formation of the blood-brain barrier by making contact with both capillaries and neurons in the CNS. Astrocytes regulate the concentration of ions in the extracellular fluid, contribute to the uptake and breakdown of neurotransmitters, and create a barrier that limits the passage of substances from the bloodstream into the brain, thereby playing a crucial role in maintaining the brain’s protected environment.
Astrocytes are star-shaped cells in the central nervous system that have many functions, including the regulation of ion concentration in the intercellular space, uptake and/or breakdown of some neurotransmitters, and the formation of the blood-brain barrier.