Protoplasmic and fibrous astrocytes are two distinct subtypes of astrocytes, which are a type of glial cell found in the central nervous system.

Protoplasmic astrocytes are typically found in the grey matter of the brain and have a relatively round or irregular cell body with numerous branching processes that form a dense, fine meshwork. These processes are relatively short and stubby, and they terminate in small, bulbous structures called endfeet, which wrap around blood vessels and synapses. Protoplasmic astrocytes play important roles in maintaining the extracellular environment around neurons and in supporting neuronal function.

In contrast, fibrous astrocytes are found in the white matter of the brain and have a more elongated cell body with fewer, longer processes that extend along axons. These processes are relatively straight and unbranched, and they do not form endfeet. Fibrous astrocytes are involved in the formation and maintenance of the myelin sheaths that surround axons in the white matter.

Both protoplasmic and fibrous astrocytes play important roles in supporting and modulating neuronal activity in the central nervous system, but they differ in their morphology, distribution, and functional roles. Understanding the differences between these two subtypes of astrocytes is important for understanding the complex interactions between glial cells and neurons in the central nervous system.