The star-shaped cells that surround neurons in the central nervous system are called astrocytes. Astrocytes are a type of glial cell, which means that they are non-neuronal cells that provide support and maintain the microenvironment of the nervous system.

Astrocytes have many functions, including providing structural support to neurons and regulating the extracellular environment of the brain. They are involved in the regulation of ions, neurotransmitters, and other chemicals that are important for proper neuronal function. Astrocytes also play a role in the formation and maintenance of the blood-brain barrier, which helps to protect the brain from harmful substances.

In addition to their supportive and regulatory functions, astrocytes also have important roles in neuronal communication and plasticity. They can release chemical messengers, called gliotransmitters, that modulate synaptic activity and contribute to learning and memory processes.

Overall, astrocytes are essential cells in the central nervous system that contribute to brain homeostasis and function. They are an important research tool for understanding brain physiology and disease.