Final answer:
Astrocytes maintain the blood-brain barrier by regulating substance transport, providing structural support to capillaries, and secreting molecules that reinforce the barrier.
Step-by-step explanation:
The role of astrocytes in maintaining the blood-brain barrier (BBB) includes several functions. Primarily, astrocytes are responsible for:
- Regulating the transport of substances between the blood and the brain. This involves controlling the passage of ions and molecules, thereby maintaining the chemical environment required for proper neuronal function.
- Providing structural support to the blood vessels that form the BBB. The end-feet of astrocytes envelop the brain's capillaries, contributing to the integrity of the barrier.
- Secreting molecules that are essential in maintaining and strengthening the BBB. These molecules help ensure that the barrier selectively blocks harmful substances from entering the brain while allowing necessary nutrients to pass through.
Considering these functions, the correct answer to the student's question is that astrocytes help maintain the blood-brain-barrier by performing all of the roles listed, including 1) regulating the transport of substances between the blood and the brain, 2) providing structural support, and 3) secreting molecules that strengten the BBB.