What is an Astrocyte? Diversity of Structures and Functions

This chapter provides an overview of astrocytes and describes the morphology and functions that depend on the specialized structural, cellular, and molecular features of astrocytes. Some cells with similarities to astrocytes are also briefly discussed. The most well studied of astrocytes as a cell type is currently the protoplasmic astrocytes of mammals. Therefore, we focus on mature mammalian protoplasmic astrocytes of mice and humans. We also describe cells that are related to astrocytes by structural and gene-protein expression similarities-across brain regions and between species. The overarching goal of this chapter is to provide a high-level current summary of astrocytes as a cell type; such understanding is needed for progress toward improved appreciation of human brain health and disease. In addition, this chapter will provide a noncomprehensive discussion of newly available techniques and tools for studying astrocytes. This is intended as a general overview and introduction to what is special about astrocytes, while providing reference to deeper coverage of astrocyte-related diseases, disorders, research methods, and current scientific questions.