There are 12 cranial nerves in the body. They come in pairs and help to link the brain with other areas of the body, such as the head, neck, and torso.
Some send sensory information, including details about smells, sights, tastes, and sounds, to the brain. These nerves are known as having sensory functions. Other cranial nerves control the movement of various muscles and the function of certain glands. These are known as motor functions.
While some cranial nerves have either sensory or motor functions, others have both. The vagus nerve is such a nerve. The cranial nerves are classified using Roman numerals based off of their location. The vagus nerve is also called cranial nerve X.
The word “vagus” means wandering in Latin. This is a very appropriate name, as the vagus nerve is the longest cranial nerve. It runs all the way from the brain stem to part of the colon.
The sensory functions of the vagus nerve are divided into two components:
Sensory functions of the vagus nerve include:
Motor functions of the vagus nerve include:
Explore the interactive 3-D diagram below to learn more about the vagus nerve.
To test the vagus nerve, a doctor may check the gag reflex. During this part of the examination, the doctor may use a soft cotton swab to tickle the back of the throat on both sides. This should cause the person to gag. If the person doesn’t gag, this may be due to a problem with the vagus nerve.
Damage to the vagus nerve can have a range of symptoms because the nerve is so long and affects many areas.
Potential symptoms of damage to the vagus nerve include:
The symptoms someone might have depend on what part of the nerve is damaged.
Experts believe that damage to the vagus nerve may also cause a condition called gastroparesis. This condition affects the involuntary contractions of the digestive system, which prevents the stomach from properly emptying.
Symptoms of gastroparesis include:
Some people develop gastroparesis after undergoing a vagotomy procedure, which removes all or part of the vagus nerve.
Sometimes the vagus nerve overreacts to certain stress triggers, such as:
Remember, the vagus nerve stimulates certain muscles in the heart that help to slow heart rate. When it overreacts, it can cause a sudden drop in heart rate and blood pressure, resulting in fainting. This is known as vasovagal syncope.
Vagus nerve stimulation involves placing a device in the body that uses electrical impulses to simulate the nerve. It’s used to treat some cases of epilepsy and depression that don’t respond to other treatments.
The device is usually placed under the skin of the chest, where a wire connects it to the left vagus nerve. Once the device is activated, it sends signals through the vagus nerve to your brainstem, which then transmits information to your brain. A neurologist usually programs the device, but people often receive a handheld magnet they can use to control the device on their own as well.
It’s thought that vagus nerve stimulation could help to treat a range of other conditions in the future, including multiple sclerosis, Alzheimer’s disease, and cluster headaches.
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