What is the role of astrocytic end-feet in the brain?

• A. They form a glial limiting membrane that contributes to the blood-brain barrier.
• B. They generate electrical impulses to regulate cerebral blood flow.
• C. They line the ventricular lumen.
• D. They secrete cerebrospinal fluid into the ventricles.

Answer: (A)

Astrocytic end-feet form a glial limitans around brain vessels and along the brain surface. This sheet of astrocyte processes wraps the capillaries and interfaces with the pia, helping to seal the neural tissue and supporting the blood-brain barrier. The end-feet not only provide a structural boundary but also send signaling cues to endothelial cells to regulate permeability and help tune blood flow in response to neuronal activity.

They do not generate electrical impulses—their signaling is typically non-electrical and involves calcium waves and release of vasoactive substances to influence blood vessels. They also do not line the ventricular lumen (that’s the role of ependymal cells) or secrete CSF into the ventricles (that’s done by the choroid plexus).