Which glial cell is most common in the brain and provides structural support for neurons, regulates the chemical environment of the synaptic gap, and helps maintain the blood-brain barrier?

• A. Microglia
• B. Oligodendrocytes
• C. Schwann cells
• D. Astrocytes

Answer: (D)

Astrocytes are the most abundant glial cells in the brain. Their star-shaped processes anchor neurons to blood vessels and provide structural support that helps organize neural networks. They actively regulate the chemical environment around synapses by buffering potassium ions and clearing excess neurotransmitters like glutamate, which keeps synaptic signaling precise and protects neurons from overexcitation. They also contribute to the blood-brain barrier by wrapping around capillaries with end-feet, helping maintain the selective permeability that protects brain tissue. Put together, these roles match the trio of structural support, synaptic chemical regulation, and barrier maintenance described in the question. Microglia are immune cells in the CNS, oligodendrocytes create myelin in the brain, and Schwann cells myelinate the peripheral nervous system, so they don’t fit all three functions as well.