The Ecology of Humans (26-19) Glia


Glia are the conductors. ~ American neurobiologist Douglas Fields

The brain has a predominant cell type: glia. Neurons account for only 15% of human brain cells. 85% are glia.

German doctor and biologist Rudolf Virchow observed glia cells through a microscope in 1858. To him, they looked like “nerve putty.” Hence, the cells of intelligence were relegated by Virchow to the Greek for “glue”: glia. German pathologist Carl Weigert furthered Virchow’s original 1858 “glue” observation, proposing that glia were structural scaffolding for nerve cells.

One of Virchow’s brilliant students, German physiologist Carl Ludwig, went against his mentor in proposing that glia and neurons signaled each other. Ludwig believed that brain functions were accomplished by an interconnected, interactive, neuronal-glial network.

A skilled illustrator and cogent writer, Spanish neurologist Santiago Ramón y Cajal elucidated and fiercely defended in the late 19th century what became known as the neuron doctrine: neurons were the cells of intelligence.

Astrocytes are a major type of glia cell. Based upon dye studies showing astrocyte connectivity, Italian physician and pathologist Camillo Golgi considered glia cells significant, though secondary, in mentation.

Golgi was a contemporaneous rival to neuron supremacist Cajal. The two men shared the 1906 Nobel prize in physiology and medicine.

Despite Golgi’s findings, which brought attention to the role of glia in the brain, Cajal’s simpler and thoroughly neuron-centric influence prevailed in scientific circles. Cajal is credited as the father of modern neurobiology, the mainstream brain ‘science’ religion.

Cajal observed that aging resulted in fewer synapses. From this he bizarrely proposed that neural synapses strengthen from learning. This wrong-headed notion resulted in generations of researchers ardently, but unsuccessfully, striving to prove it. The cloistered world of neurobiology diligently pursued blind alleys rather than question unfounded presumptions. Because of Cajal and his disciples, glia went unstudied for 6 decades.

Glia are still generally considered brain stuffing by neurobiologists, largely filling void space, performing some housekeeping functions for the nerve cells that are considered the center of thought.

The evidence is building up that we can explain everything interesting about the mind in terms of interactions of neurons. ~ Canadian cognition philosopher Paul Thagard in 2015

Into this century neurons are regularly credited with the accomplishments of glia. Nerve cell transitions were studied while astrocytes were studiously ignored. Only in the 2nd decade of the 21st century has this begin to change.

Misattribution is easily had by carelessly mistaking effect for cause. One cannot see what is not looked at, or looked askew via a predetermined perspective. In academic disciplines, only economics has proceeded with as much built-in bias as neurobiology: a shameless disgrace to science.

◊ ◊ ◊

Neurons are utterly dependent on glia to fire their electrical impulses. ~ Douglas Fields

Neurobiologists long assumed that neurons were the governors of consciousness, particularly the transition between sleep and the awake state. Instead, that physiological transition occurs through ion flows regulated by glia.

Once dismissed as mere packing material, glia make up 85% of the cells in our brain, and are now known to control many of the brain’s functions. Astrocytes ferry nutrients and waste and mediate neuronal communication. Oligodendrocytes coat axons with insulating myelin, boosting signal speeds. Microglia fight Infection and promote repair; when they fail, so does the brain. ~ Douglas Fields

Hunger is monitored and its response physiologically controlled by glia, not neurons. This is done by regulating the release of the hormones leptin and ghrelin, which control the sensation of hunger and adjust energy expenditure. The effects of leptin and ghrelin on metabolism come by commanding neural circuits.

Neural activity patterns do not correlate with those of mentation. After extensive study of nerve cells for well over a century, neurobiologists still cannot explain memory via neurons.

By regulating the synapses, glia control the transfer of information between neurons. ~ Italian neurobiologist Maurizio De Pittà

Via ionic calcium waves, glia signal each other in a way that indicates information storage. Neurons have no memory capacity beyond that of other soma cell types. That’s because the physical correlate of mentation transpires in glia, not nerves.

In the brain, astrocytes control how many new neurons are formed from neural stem cells and survive to integrate into the existing neuronal networks. Astrocytes do this by secreting specific molecules, but also by much less understood direct cell-cell interactions with stem cells. ~ Swedish neurobiologist Milos Pekny

Glia guide developing neurons, form myelin, sop up chemicals used in cell-to-cell communication, manage brain washing during sleep for its rejuvenating effect, and generally contribute to the health and well-being of nerve cells and their environment. And glia do much more. Glia are the adult stem cells in the brain: able to reproduce themselves, and neurons if need be. Glia regenerate and grow locally to store more information.