Introducing the brain: the vagus nerve (Introduction)

by David Turell , Friday, August 25, 2023, 00:37 (456 days ago) @ David Turell

The tenth cranial nerve has a multitude of controls of bodily functions:

https://www.newscientist.com/article/mg25934530-500-unravelling-the-secrets-of-the-vagu...

"...recent research has revealed the vagus nerve’s role in a wider array of processes than we ever realised – not only monitoring organ function, but helping discern facial expressions and even regulating mood. Most enticingly, we are starting to understand how it governs inflammation, the immune response that runs rampant in conditions ranging from heart disease to Parkinson’s.

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"The vagus nerve is a bundle of neural fibres that starts at the brain stem. It splits into two channels that run along either side of the neck, then rejoin at the heart before descending to the gut and other organs.

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"Subsequent experiments revealed that the vagus nerve regulates functions of the heart, stomach, lungs, liver and more. But it wasn’t until about three decades ago that we began to tap into it for medical treatments.

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"Most tantalising is the role the vagus nerve plays in controlling inflammation. Hints of this first emerged in the 1990s, when Kevin Tracey, now at the Feinstein Institutes for Medical Research, and his colleagues developed an anti-inflammatory drug to block production of proteins called cytokines, which spur the body’s immune response to infection or illness. In modest amounts, cytokines and the ensuing inflammation fend off foreign pathogens and heal injuries, but an overabundance of them has the opposite effect, damaging tissues and potentially causing chronic illness or even organ failure.

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"Tracey dubbed the vagus nerve’s ability to mediate inflammation the inflammatory reflex. It kicks in when specialised neurons detect cytokines and send signals to the brain, which in turn relays messages to the spleen to start churning out white blood cells. The discovery suggested that we might be able to interrupt inflammation with an electrode, not just drugs, he says.

"In 2012, a device using an electrode that Tracey designed while at SetPoint Medical, a biotechnology company in California, was tested in a small group of people with the chronic inflammatory condition rheumatoid arthritis. Of those, 70 per cent had at least a 20 per cent reduction in symptoms, and almost half saw a 50 per cent improvement.

"The effect is similar to that of some drugs, but there is a major advantage: anti-inflammatory medications often severely suppress immune function, leaving people vulnerable to infection. Not so with this approach. Vagus nerve stimulation causes white blood cells to shut down cytokine production enough to avoid runaway inflammation, but not so much that our immune system is disarmed completely, says Tracey.

"SetPoint Medical is now conducting a trial of the device in about 250 people. Tracey is hopeful that the FDA could approve the treatment for rheumatoid arthritis within a few years. Meanwhile, similar devices have also shown promise in treating conditions characterised by chronic inflammation, including inflammatory bowel disease, multiple sclerosis and Parkinson’s disease.

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"We can tell what types of signals neurons ferry based on their distinct anatomical features. Afferent neurons transmit sensory information towards the brain, while efferent neurons relay signals for controlling movement from the brain to our muscles. Fibres that are insulated in a fatty coating called myelin generally fire faster than those without it. “So, if it is myelinated and efferent, we know that most likely mediates muscle contractions,” says Zanos.

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"Stephen Liberles at Harvard University believes we can achieve even greater precision by elucidating the mechanisms of specific neurons with genetic sequencing. Of particular interest are sensory neurons, which constitute about 80 per cent of all nerve fibres in the vagus and use specialised receptors to detect changes in an environment. “Some of our landmark discoveries in the external senses were discovering odourant receptors or vision receptors,” says Liberles. “We don’t know the receptors for almost any internal organ sense.”

"Already, he and his colleagues have identified previously unknown types of vagal neurons that mediate breathing, control blood pressure and detect nutrients in the gut.

Comment: Previous entries about gut connection:

2021-03-03, 20:50; 2020-09-04, 20:46; 2018-12-05, 20:55

The Vagus, as a direct brain nerve, offers feedback sensory and motor information, just like all the feedback biochemical controls in working cells. A master design of this sort cann ot develop by chance. Taken from an article about stimulation of the Vagus.