Glial cells

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A note for Lesson no. 2, "Your Brain Is a Network," in Seven and a Half Lessons About the Brain by Lisa Feldman Barrett.
Some context from page 46 is:

...other kinds of brain cells, called glial cells, that function in ways that scientists don’t fully understand yet.

Glial cells are brain cells that are not neurons. There are about 60 billion glial cells in the human brain when counted by stereology.[1] Scientists have learned some things about the various functions of glial cells:[2][3]

  • Astrocyctes are the most common cells in the central nervous system. They wrap around the gaps between neurons, called synapses, and regulate the chemical environment during synaptic transmission to make neural communication more or less efficient. They help to clear excess neurotransmitters from the synaptic space.[4]
  • Oligodendrocytes help to wrap the axons of neurons which speeds their ability to convey information electrically (i.e., they create the myelin sheath around the axon of a neuron to speed the movement of the action potential).[5]
  • Microglia control inflammation in the brain and kill neurons (to improve metabolic efficiency). This can be helpful (e.g., neural pruning during childhood) or contribute to illness.[6]
  • Radial glia guide brain development by helping neurons, after they are born, to migrate to their proper location.[7]

Much is still unknown about glial function, earning glial cells the nickname “the dark matter of the brain.” Scientists used to think that glial cells merely supported neurons, but now it appears they have many functions and may even share information with one another.


  1. Walløe, Solveig, Bente Pakkenberg, and Katrine Fabricius. 2014. “Stereological Estimation of Total Cell Numbers in the Human Cerebral and Cerebellar Cortex.” Frontiers in Human Neuroscience 8: 508.
  2. Allen, Nicola J. and David A. Lyons. 2018. “Glia as Architects of Central Nervous System Formation and Function.” Science 362: 181–185.
  3. García-Cabezas, Miguel Á., Yohan J. John, Helen Barbas, and Basilis Zikopoulos. 2016. “Distinction of Neurons, Glia and Endothelial Cells in the Cerebral Cortex: An Algorithm Based on Cytological Features.” Frontiers in Neuroanatomy 10: 107.
  4. Sofroniew, Michael V., and Harry V. Vinters. 2010. "Astrocytes: Biology and Pathology." Acta Neuropathologica 119 (1): 7–35.
  5. Bradl, Monika, and Hans Lassmann. "Oligodendrocytes: Biology and Pathology." Acta Neuropathologica 119 (1): 37–53.
  6. Li, Qingyun, and Ben A. Barres. "Microglia and Macrophages In Brain Homeostasis and Disease." Nature Reviews Immunology 18 (4): 225.
  7. Kriegstein, Arnold R., and Magdalena Götz. 2003. "Radial Glia Diversity: A Matter of Cell Fate." Glia 43 (1): 37–43.