Which statement best describes astrocytes' role at synapses?

Which statement best describes astrocytes' role at synapses?

• A. They generate action potentials in neurons.
• B. They are the primary source of myelin in the CNS.
• C. They store neurotransmitters in vesicles for release.
• D. They take up neurotransmitters from the synaptic cleft and regulate ions and energy supply.

Answer: (D)

Astrocytes at synapses help keep the chemical environment stable and ready for signaling. They wrap around the synapse and actively take up neurotransmitters released into the cleft (such as glutamate and GABA), which terminates the signal and prevents excessive stimulation. They also buffer extracellular potassium that accumulates when neurons fire, helping maintain the right ionic conditions for neuronal excitability. Beyond clearing transmitters and buffering ions, astrocytes supply energy to neurons. They can convert glucose to lactate and shuttle it to neurons, supporting ongoing activity when energy demand is high. Altogether, their combined roles in clearing neurotransmitters, regulating ions, and providing metabolic support fit best with this description. In contrast, they do not generate action potentials, they are not the primary source of CNS myelin (that’s done by oligodendrocytes), and they do not store neurotransmitters in vesicles for release in the way neurons do.

Astrocytes at synapses help keep the chemical environment stable and ready for signaling. They wrap around the synapse and actively take up neurotransmitters released into the cleft (such as glutamate and GABA), which terminates the signal and prevents excessive stimulation. They also buffer extracellular potassium that accumulates when neurons fire, helping maintain the right ionic conditions for neuronal excitability.

Beyond clearing transmitters and buffering ions, astrocytes supply energy to neurons. They can convert glucose to lactate and shuttle it to neurons, supporting ongoing activity when energy demand is high. Altogether, their combined roles in clearing neurotransmitters, regulating ions, and providing metabolic support fit best with this description.

In contrast, they do not generate action potentials, they are not the primary source of CNS myelin (that’s done by oligodendrocytes), and they do not store neurotransmitters in vesicles for release in the way neurons do.