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What is the vagus nerve?
We have 12 cranial nerves. The vagus nerve is the tenth and longest of all. It starts in the part of the brainstem called the medulla, at the back of the brain. It then extends from the base of the skull along the neck, through the torso, and to the colon in the lower abdomen. Its name comes from the Latin word for "wanderer." It wanders throughout the body, connecting organs to the brainstem.
The nervous system provides two-way communication between the brain and body. The vagus nerve is one of the most important nerves, communicating with the body's major organs and systems and transmitting information back and forth to the brain. It also controls or plays a vital role in many of the body's sensory, physical, and hormonal functions and activities.
Why is the vagus nerve so unique?
It is the only cranial nerve that extends to the thoracic and digestive organs. The vagus nerve is a key player in the parasympathetic nervous system, which is part of the autonomic nervous system. The parasympathetic nervous system manages rest and digestion, among other things.
The vagus nerve has three functional pathways:
- the visceral efferent pathway;
- the motor efferent pathway; and
- the afferent pathway.
Efferent pathways are motor outputs. These are neurons that carry information from the central nervous system to the body's organs, muscles, and tissues. An afferent nerve does the opposite: it carries peripheral signals back to the central nervous system. In other words, an afferent pathway transmits sensory inputs to the nervous system.
The influence of the vagus nerve on our well-being
The vagus nerve is a major anatomical and physiological player in vital bodily functions and deep well-being. It is essential for the homeostasis of the cardiovascular, gastrointestinal, and respiratory systems.
It controls the body's unconscious activities, such as heart rate, breathing, and sensory communication between organs. It also plays a role in higher-level physiological functions, such as gut-brain communication and relaxation. The vagus nerve is therefore essential for our most basic life needs and helps keep us healthy.
Vital physiological functions related to the vagus nerve:
- breathing;
- heart rate control;
- speech;
- hearing;
- movement of the digestive tract;
- swallowing and gag reflex;
- blood pressure;
- bladder function; and
- sensory processes (pain, touch, temperature).
Respiratory function
The vagus nerve induces the release of a neurotransmitter called acetylcholine, which tells your respiratory system to breathe. Slow, long, and deep breathing exercises are one way to stimulate your vagus nerve. The vagus nerve also works through breathing to help our bodies relax during times of stress.
Heart rate control
Acetylcholine also helps slow the heart rate. The vagus nerve transmits sensory information from the aorta via baroreceptors and chemoreceptors. Baroreceptors send information about blood pressure throughout the circulatory system. Chemoreceptors provide information about blood oxygen levels via the vagus nerve. As the main nerve of the parasympathetic nervous system, the vagus nerve helps slow the heart rate during or after times of stress. If the vagus nerve isn't functioning properly, it can take much longer for the body to calm down after a stressful event, exposing it to even more damaging stress hormones.
Speech and swallowing
The vagus nerve supplies nerves to the muscles of the pharynx and larynx, which help us speak and swallow. It also plays a role in the gag reflex, which is essential for protecting our airways from food, liquids, or foreign bodies. When the throat muscles are relaxed, breathing is easier, which helps maintain the health of the vagus nerve system.
Contributions of the vagus nerve to deep well-being:
- it calms the nervous system;
- it plays a role in the sense of taste;
- it helps communicate the feeling of satiety;
- it fights inflammation;
- it ensures the gut-brain connection;
- it reduces stress and promotes relaxation;
- it contributes to the formation of memory; and
- It contributes to sexual health and fertility.
Anti-inflammation
Inflammation is part of the immune system's normal response to illness or injury. Through its extensive sensory network, the vagus nerve detects when the body produces substances such as cytokines or other markers of inflammation. It then signals the brain to produce anti-inflammatory neurotransmitters. This regulates the immune system's response and protects the body from the harmful effects of chronic inflammation.
Stress reduction and relaxation
When faced with stress, the sympathetic nervous system puts the body into a "fight or flight" state, vital for human survival. This system tells us when something is wrong, whether it's trauma in a truly dangerous situation, or a less problematic event like a negative interaction with a coworker that makes you uncomfortable. Our body's initial response to these events may be due to the calming effects of the vagus nerve.
The sympathetic nervous system releases adrenaline and cortisol, two hormones necessary for our survival. A part of the parasympathetic nervous system, the vagus nerve releases the neurotransmitter acetylcholine. It also directs other parts of the body to release neurotransmitters like oxytocin and vasopressin, which also help calm the body after stressful interactions.
Gut-Brain Connections
The vagus nerve is the only cranial nerve that extends far enough to reach the intestine. This two-way communication between the gut and the brain promotes the feeling of satiety (when the body signals the brain that it is no longer hungry).
Beyond diet-related issues, the vagus nerve contributes significantly to mental health during times of stress and trauma and the body's response. Most of the body's neurotransmitters, such as serotonin, are produced in the gut. Pain, healthy weight management, and glucose/insulin regulation are all linked to stress and mental well-being.
Summary :
- The vagus nerve is the longest cranial nerve and the one that extends the furthest in our body.
- It connects the brain to most of the body's organs and functioning systems.
- It slows down the heart rate and regulates blood pressure.
- It stimulates breathing.
- It processes sensations such as touch, temperature and pain.
- The vagus nerve plays a key role in rest and digestion and contributes even more broadly to stress reduction and relaxation.