Glia

Glial cells are non-neuronal cells that play a crucial role in brain function. They make up around half of the total volume of the brain and are often referred to as "support cells" because they provide a stable environment and support neurons.

There are several types of glial cells, each with specific functions. Astrocytes are the most abundant glial cells and are involved in regulating neuronal communication, maintaining homeostasis and protecting neurons from damage. Oligodendrocytes produce the myelin that surrounds the axons of neurons, speeding up the transmission of nerve signals. Microglia are the brain's immune cells and play an important role in the response to injury and infection.

Glial cells are also involved in neurological diseases such as multiple sclerosis, Alzheimer's disease and Parkinson's disease. 

In short, glial cells are non-neuronal cells in the brain that play an important role in regulating neuronal activity, maintaining homeostasis and protecting neurons. Understanding them is essential for a better understanding of normal brain function and neurological diseases.