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THE VAGUS NERVE

The influence of the vagus nerve on health and well-being.

The Vagus nerve, originating in the brain stem, is the 10th cranial nerve and is responsible for the parasympathetic control of the majority of our internal organs including the heart, the lungs and digestive tract. Therefore, it has a significant impact on our health and well-being.

Vagus Nerve and the Parasympathetic Nervous System.

The autonomic nervous system carries out all of the functions of the body we do not have to consciously control. It is divided into the sympathetic and parasympathetic nervous system. The vagus nerve, the longest nerve of the autonomic nervous system in the human body, is the primary component of the parasympathetic nervous system. It regulates heart rate, breathing rate, peristalsis, sweating, detoxification and much more.
 

 

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Vagus Nerve and Stress.

The vagus nerve has two branches, the dorsal vagus complex (DVC) and the ventral vagus complex (VVC). The dorsal vagus complex is the more primitive unmyelinated branch of the vagus nerve and when activated, produces the freeze response. The ventral vagus complex (VVC) is the newer myelinated branch of the vagus nerve and is known as the social engagement system.
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Dr. Stephen Porges’ poly-vagal theory explains how the nervous system responds to stress or danger. It describes a three-part hierarchical system:
1. Ventral vagus activation – relaxation and social engagement. (We feel engaged and grounded).
2. Sympathetic activation -fight or  flight. (We feel scared, angry, worried etc.).
3. Dorsal vagus activation – immobilization or freeze. (We feel depressed, numb, hopeless etc.).
Therefore, in everyday, safe situations, if we are emotionally healthy, our bodies stay in a happy, relaxed state. In stressful situations, the sympathetic nervous system, our immediate reaction to stress and danger, kicks in to action. This resulting fight or flight state is designed to keep us alive. In fight or flight, at some level, we believe we can still survive the threat we’re facing in that moment. However, if the sympathetic nervous system hasn’t been able to ward off the danger, the dorsal vagal system takes control, causing us to freeze or shut down as a form of self preservation.
Ideally, we would live predominantly in a relaxed state, activate the fight or flight response when we face real danger, then reactivate the relaxation response after the danger has passed. However, most people live in a constant stress state due to chronic fears and anxieties, dwelling on the past or worrying about the future. This chronic activation of the sympathetic nervous system, causes weakening of the parasympathetic nervous system and disrupts the natural balance of the autonomic nervous system.

Chronic disease states are associated with either the fight or flight response or the freeze response. However, no healing or regeneration takes place during fight, flight or freeze activation. We can only heal when our relaxation response (ventral vagus nerve) is activated.

Vagus Nerve and the gut-brain-microbiome connection.

The gut-brain axis is a term for the communication network that connects the gut and the brain. This system is complex but the vagus nerve is one of the key elements of this connection. The vagus nerve sends signals in both directions – 80% of the information transmitted by the vagus nerve flows from the body to the brain and 20% of the vagus nerve is transmitted from the brain to the body. Therefore, the gut microorganisms affect the brain, and the brain, (our thoughts and emotions), affects the gut.
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In animal studies, stress inhibits the signals sent through the vagus nerve and causes gastrointestinal problems. Poor vagus nerve function explains why stress suppresses stomach acid and digestive enzyme production, increases gut permeability (leaky gut), reduces the Migrating Motor Complex (the main cause of SIBO), contributes to dysbiosis and nutrient malabsorption.

Chronic disease states are associated with either the fight or flight response or the freeze response. However, no healing or regeneration takes place during fight, flight or freeze activation. We can only heal when our relaxation response (ventral vagus nerve) is activated.

Vagus Nerve and the Immune System.

Inflammation is a healthy immune system response, which serves to protect and repair the body from something damaging. After it has served its purpose, a well-functioning vagus nerve sends signals to shut down inflammation via the cholinergic anti-inflammatory pathway. However, if the inflammation is not switched off, it becomes chronic. 
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Chronic inflammation is the most common sign of poor vagus nerve function. It is associated with almost all chronic illness. Research shows that those with inflammatory conditions often have decreased heart variability, which is a marker of reduced vagal tone. This is associated with high levels of pro-inflammatory cytokines and an increase in sympathetic nervous system activity and stress hormones, which contributes to systemic inflammation.

Chronic disease states are associated with either the fight or flight response or the freeze response. However, no healing or regeneration takes place during fight, flight or freeze activation. We can only heal when our relaxation response (ventral vagus nerve) is activated.

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