Introducing the brain: right and left vagus nerves (Introduction)

by David Turell , Monday, August 26, 2024, 23:15 (87 days ago) @ David Turell

Control of all the body:

https://www.quantamagazine.org/how-our-longest-nerve-orchestrates-the-mind-body-connect...

"The supreme organ gives most people a vivid sensory perception of the world. It can preserve memories, enable us to learn and speak, generate emotions and consciousness. But those who might attempt to preserve their mind by uploading its data into a computer miss a critical point: The body is essential to the mind.

"How is this crucial brain-body connection orchestrated? The answer involves the very unusual vagus nerve. The longest nerve in the body, it wends its way from the brain throughout the head and trunk, issuing commands to our organs and receiving sensations from them. Much of the bewildering range of functions it regulates, such as mood, learning, sexual arousal and fear, are automatic and operate without conscious control. These complex responses engage a constellation of cerebral circuits that link brain and body. The vagus nerve is, in one way of thinking, the conduit of the mind.

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"The vagus nerve is one of 13 nerves that leave the brain directly through special holes in the skull. From there it sprouts thickets of branches that reach almost everywhere in the head and trunk. The vagus also radiates from two major clusters of outpost neurons, called ganglia, stationed in critical spots in the body. For example, a large cluster of vagal neurons clings like a vine to the carotid artery in your neck. Its nerve fibers follow this network of blood vessels throughout your body to reach vital organs, from the heart and lungs to the gut.

"As with the brain itself, with its mirrored left and right hemispheres, we have left and right vagus nerve branches, which connect to the two hemispheres. But the organs in our body are not bilaterally symmetrical: The heart is on the left side and the liver is on the right, for example. The right vagal nerve, then, is longer than the left, and the two sides have distinct functions because of the different organs they entwine.

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"All complex body systems require the equivalent of brakes and a gas pedal to maintain control, and the vagus nerve serves these roles for many of our innate responses, nearly all of which occur involuntarily. Signals between the brainstem and the body travel up and down the nerve to twist your gut for digestion, marshal your immune system to keep microbial threats at bay, pace your heart, and dial your blood pressure up and down. The vagus nerve squeezes your bronchial tubes to pipe air into your lungs, triggers your gag reflex and makes you cough.

"Its influence goes beyond basic life support: The vagus nerve is critical to generating mind by integrating the brain and body. Choking is terrifying because death could be mere minutes away. That heightened mental state is dependent on signals coming from the body — the inability to breathe or swallow — and the vagus nerve both senses and controls the choking response. If your heart suddenly starts racing, you might experience a panic attack; controlling heart rate is a prime function of the vagus nerve. Many other mental states, sexual arousal for example, depend on the mind-body connection that involves information going to the brain (sensual touching, for example) and out of the brain (to arouse bodily responses). The vagus nerve is that connection. Its length and widespread nature throughout the brain as well as the body allow it to coordinate such diverse bodily functions in a way that independent nerves could not.

"The primary function of the vagus nerve is to dampen the body’s responses. After a fear episode, for example, the body’s powerful, life-saving threat response must be terminated to restore resting heartbeat, respiration, blood flow and the rest. So powerful is its influence, the vagus nerve can literally stop the beating heart. Conversely, the vagus nerve can also stimulate bodily responses by releasing the brakes to accelerate."

Comment: the necessary influences of the vagus are truly amazing. You feel like vomiting, thank your vagus. You get excited, and your heart races, the vagus again. Many of the control centers are in the hypothalamus at the underside of the brain where the vagus attaches. We are aware of our insides through the two Vagi, a sensation called interoception. After seeing this arrangement can one doubt design?