brain complexity: glial cells have functions (Introduction)

by David Turell , Tuesday, January 28, 2020, 00:13 (1550 days ago) @ David Turell

New findings show their many important functions:

https://www.quantamagazine.org/glial-brain-cells-long-in-neurons-shadow-reveal-hidden-p...

"The sting of a paper cut or the throb of a dog bite is perceived through the skin, where cells react to mechanical forces and send an electrical message to the brain. These signals were believed to originate in the naked endings of neurons that extend into the skin. But a few months ago, scientists came to the surprising realization that some of the cells essential for sensing this type of pain aren’t neurons at all. It’s a previously overlooked type of specialized glial cell that intertwines with nerve endings to form a mesh in the outer layers of the skin. The information the glial cells send to neurons is what initiates the “ouch”: When researchers stimulated only the glial cells, mice pulled back their paws or guarded them while licking or shaking — responses specific to pain

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“'In the human brain, glial cells are as abundant as neurons are. Yet we know orders of magnitude less about what they do than we know about the neurons,” said Shai Shaham, a professor of cell biology at the Rockefeller University who focuses on glia. As more scientists turn their attention to glia, findings have been piling up to reveal a family of diverse cells that are unexpectedly crucial to vital processes.

"It turns out that glia perform a staggering number of functions. They help process memories. Some serve as immune system agents and ward off infection, while some communicate with neurons. Others are essential to brain development. Far from being mere valets to neurons, glia often take leading roles in protecting the brain’s health and directing its development. “Pick any question in the nervous system, and glial cells will be involved,” Shaham said.

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"Several cell types are contained within the umbrella category of glia, with varied functions that are still coming to light. Oligodendrocytes and Schwann cells wrap around nerve fibers and insulate them in fatty myelin sheaths, which help to confine the electrical signals moving through neurons and speed their passage. Astrocytes, with their complex branching shapes, direct the flow of fluid in the brain, reshape the synaptic connections between neurons, and recycle the released neurotransmitter molecules that enable neurons to communicate, among other jobs.

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"The work is exposing how microglia respond to brain trauma and other injuries, how they suppress inflammation, and how they behave in the presence of neurodegenerative diseases. The cells “really are at the edge between immunology and neuroscience,” Sierra said.

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"In recent years, microglia have been found to mimic the macrophages of the immune system by engulfing threats to the brain such as cellular debris and microbes. Microglia also seem to go after obsolete synapses. “If you live-image them, you can see them eating neurons,” Brown said.

"Some of these active functions are shared with other types of glia as well. Astrocytes and Schwann cells, for example, may also prune synaptic connections. But despite the commonalities among different subsets of glia, researchers are starting to realize that there’s little to unify glial cells as a group.

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"Neurons and glia cannot function independently: Their interactions are vital to the survival of the nervous system and the memories, thoughts and emotions it generates. But the nature of their partnership is still mysterious, notes Staci Bilbo, a professor of psychology and neuroscience at Duke University. Glia are gaining a reputation for the complexity long attributed to neurons, but it’s still unclear whether one cell type primarily directs the other. “The big unknown in the field is: Who is driving the response?” she said."

Comment: Considering what brains do and control, this degree of complexity is not surprising, and this aspect of brain cellular function is only partially understood. Certainly designed.