What percentage of brain cells are glial cells?

Glial cells, also known as neuroglia or simply glia, are non-neuronal cells that provide support and protection for neurons in the nervous system. It is well-established in neuroscience that glial cells constitute a significant proportion of the total cell population in the brain, with estimates suggesting that they make up about 90% of the total brain cells.

This high percentage reflects the essential roles that glial cells play, which include supporting neuronal function, maintaining homeostasis, forming myelin, and providing a framework for the nervous system. They are critical for processes such as nutrient support, waste removal, and the modulation of neurotransmission.

The other choices do not accurately represent the current understanding of glial cell prevalence in the brain. For instance, while 50% and 75% suggest a smaller proportion, which underrepresents the significant presence of glial cells, the suggestion of 100% implies that there are no neurons present at all, which is inaccurate as neurons are indispensable components of the brain.

Therefore, the correct understanding is that glial cells comprise approximately 90% of the brain's cell population, emphasizing their importance in both structure and function within the central nervous system.