Which of the following describes a function of astrocytes?

• A. They generate action potentials.
• B. They regulate the extracellular space, clear neurotransmitters, and limit diffusion.
• C. They form the myelin sheath in the CNS.
• D. They produce cerebrospinal fluid.

Answer: (B)

Astrocytes primarily manage the environment around neurons. They sit in the CNS and shape how signals spread by keeping the extracellular space stable and clean. One key job is clearing neurotransmitters from the synaptic cleft, such as glutamate and GABA, through specialized transporters. This terminates the signal and prevents spillover that could unintentionally activate neighboring synapses. By buffering ions like potassium, astrocytes help maintain the right ionic conditions for neurons to fire reliably, which in turn also limits how far signaling molecules diffuse away from the synapse. Their endfeet wrap around blood vessels and synapses, helping regulate diffusion and contribute to the overall homeostasis of the neural environment.

Some choices don’t fit because they describe functions of other cell types. Generating action potentials is something neurons do, not astrocytes. Forming the myelin sheath in the CNS is the job of oligodendrocytes. Producing cerebrospinal fluid is done by the choroid plexus epithelium, not astrocytes.