A Complete Guide to Your Vagus Nerve
Medically reviewed by Smita Patel, DO
The vagus nerve (also called the vagal nerve) is one of the 12 cranial nerves, which are nerves that start in the brain and control most body functions. It is the tenth cranial nerve, and medical scientists typically describe it as the longest cranial nerve.
From its origin in the brain, the vagus nerve sends many nerve fibers to organs and tissues. Nerve fibers are cordlike projections from your neurons (nerve cells). These nerve fibers and their branches control the functions of glands and smooth muscles in most of your internal organs.
Vagus nerve damage or injury can lead you to develop various medical conditions. These include problems with speech or swallowing and gastrointestinal dysfunction, which could lead to digestive issues.
Design by Health
Anatomy of the Vagus Nerve
The autonomic nervous system is a part of your nervous system, which altogether makes up your brain, spinal cord, and the nerves throughout your body. The autonomic nervous system controls unconscious activities such as digestion, sweating, and breathing. It consists of two parts, which are the sympathetic nervous system and the parasympathetic nervous system.
The sympathetic nervous system controls your “fight or flight” response, which enables you to fight or flee when you face danger. In contrast, the parasympathetic nervous system allows you to rest and relax.
The two autonomic nervous systems function to help keep your body in a balanced state.
Structure
Your vagus nerve consists of two different types of nerve fibers. First, there are somatic nerves, which control sensations around your skin and muscles. The second type is visceral fibers, which regulate the functions of your internal organs.
The vagus nerve starts from the medulla oblongata, which is a region found in the base of your brain. It exits the skull through the jugular foramen, a small channel at the base of your skull. Outside the brain, the vagus nerve connects and distributes nerve branches. Most of these nerve fibers supply nerve impulses to your local connective tissues, blood vessels, and organs, directing them as to what they should do.
Location
The right and left vagus nerves exit your brain and travel downwards in your neck. They lie along the carotid sheaths, which are protective covering of connective tissues.
Here, both vagus nerves are close to the major blood vessels in your neck. These are the internal and common carotid arteries and the internal jugular vein.
In the neck, the vagus nerve divides into four major nerve branches—pharyngeal branches, the superior laryngeal nerve, the recurrent laryngeal nerve, and the superior cardiac nerve. These nerves control the muscles and vessels in your neck.
As the vagus nerve descends, it enters your lung cavities (the air space within your lungs) and intestines. At these locations, it divides into multiple terminal nerve fibers that supply the blood vessels, connective tissues, and internal organs in these regions with nerve impulses.
Anatomical Variations
The course and distribution of the vagus nerves vary for each person. A 2022 research study findings suggested that the vagus nerve had different anatomical locations in 34% of the study participants.
Also, some studies have found significant anatomical variability of the vagus nerve. The common place is at the esophageal hiatus. This is the opening in the diaphragm where the esophagus passes into the abdominal cavity.
Awareness of these anatomical variations in the vagus nerve is crucial for surgeons. This is because the vagus nerve is at risk of injury during surgeries around the neck or the area between the stomach and esophagus. Surgeons must be aware of these variations so they can operate with caution to prevent accidental injuries.
What Does the Vagus Nerve Do?
The vagus nerve works by using its branches to provide both sensing and controlling signals to many organs. Also, the brain controls most systemic functions in the body through its connection with vagus nerve fibers.
Involuntary functions of the vagus nerve include:
Breathing: The vagus nerve branches in the lung cavity control your breathing. They coordinate the rhythmic movements of your diaphragm and rib cage muscles.
Gastrointestinal functions: The vagal nerve fibers also control the function of your stomach and intestines, such as bowel movements and the production and discharge of gastrointestinal digestive enzymes.. These activities are necessary for proper digestion of the food you eat.
Cardiovascular functions: The heart and the blood vessels form the cardiovascular system. The vagus nerve fiber to the neck supplies your heart muscles and blood vessels with nerve impulses. These fibers control muscular contractions, blood pressure, heart rate, and rhythm. The vagus nerve regulates your heart rate, blood pressure, and the force of contraction in the heart muscles.
Other involuntary actions: The vagus nerve sends sensory and motor fibers to various tissues. This includes skin receptors (nerve endings that allow you to feel sensations on your skin) and smooth muscles in the neck and intestine. These nerve branches control coughing, sneezing, salivation, swallowing, and vomiting.
Medical conditions such as large tumors can press on these vagal nerve fibers. This could result in functional damage to your organs.
Associated Conditions
Although uncommon, some surgical procedures can also damage vagal nerve branches. The signs and symptoms of vagus nerve injury vary for each person. It also depends on the exact location and intensity of the nerve damage.
Speaking and Swallowing Difficulties
Speaking difficulties occur due to Injury to the vagus nerve branch that supplies the larynx, which is the voicebox. Difficulty swallowing occurs due to injury to the nerve supplying the throat.
These injuries are most likely to occur during throat surgeries. Individuals may present with the following symptoms:
Cracky or hoarse voice
Altered pain sensations around the affected area
Gag reflex loss (the back of the throat loses its ability to respond to touch or stimulus){²}
Cardiovascular Dysfunction
Damage to the vagal nerve fibers to the heart and blood vessels can alter your heart rate, blood pressure, and the force of your heart’s contraction
Symptoms of cardiovascular dysfunction due to vagal nerve injury typically include:
Abnormal heart rate, which may be lower or higher
Fainting spells
Gastrointestinal Dysfunction
Vagal nerve injury to the gastrointestinal tract can interfere with your digestive process. This can affect digestive enzyme secretion, cause smooth muscle paralysis. and ultimately interrupt your bowel movements.
Symptoms of gastrointestinal dysfunction include:
Diagnostic Testing
Various assessment methods can be used to check the function of your vagusnerve. These diagnostic tests are typically needed If you suspect you have symptoms that suggest a vagus nerve injury.
Here are some of the common methods used to assess your vagus nerve.
Clinical Assessment
As part of your assessment, your healthcare provider will review your medical history and conduct a physical exam.
During the physical examination, your healthcare provider may ask you to open your mouth and say a word like “Aah”. During this process, they will stimulate your throat to assess your gag reflex.
A normal gag reflex and a healthy tone in the smooth muscles around your throat are typically suggestive of a normal vagal nerve response.
Valsalva Maneuver
The Valsalva maneuver is a technique in which your healthcare provider instructs you to close your mouth, pinch your nose, and then forcefully exhale. This breathing technique should ideally stimulate your vagus nerve’s parasympathetic effects such as slowing down your heart rate, etc. However, this assessment requires caution. It may create sudden blood pressure changes, which may not be suitable for some people.
Tips for Keeping Your Vagus Nerve Healthy
Proper dietary and lifestyle activities can assist in keeping your vagus nerve healthy.
The following are some examples of healthy lifestyle choices and foods to consider:
Regular deep breathing practices
Yoga
Light to moderate intense physical activities such as walking
Intake of anti-inflammatory foods like salmon, green leafy vegetables and fruits such as berries.
A Quick Review
The vagus nerve is one of the cranial nerves that emerges from the brain. It extends widely into multiple tissues and organ systems.
Its nerve branches supply many glands, smooth muscles, and organs with nerve fibers. These nerve fibers control involuntary functions like breathing and digestion. Compression from large tumors or surgery could damage the vagus nerve fibers. Damage or injury to the vagus nerve may cause dysfunction of multiple organs. This could cause symptoms such as low blood pressure, abnormal heart rhythm, bloating, and vomiting.
Vagal nerve testing is typically helpful if you suspect you have symptoms that indicate possible vagal nerve injury.
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