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he vagus nerve is the longest and most
complex of the 12 pairs of cranial nerves that emanate from the brain. It
transmits information to or from the surface of the brain to tissues and organs
elsewhere in the body.
The
name "vagus" comes from the Latin term for "wandering."
This is because the vagus nerve wanders from the brain into organs in the neck,
chest, and abdomen.
It is also known as the 10th cranial nerve or cranial
nerve X.
What is the vagus nerve?
The vagus nerve is one of the cranial nerves that connect the brain to the body.
The vagus nerve has two
bunches of sensory nerve cell bodies, and it connects the brainstem to the
body. It allows the brain to monitor and receive information about several of
the body's different functions.
There are multiple nervous system functions provided by
the vagus nerve and its related parts. The vagus nerve functions contribute to
the autonomic nervous system, which consists of the parasympathetic and
sympathetic parts.
The nerve is responsible for certain sensory activities
and motor information for movement within the body.
Essentially, it is part of a circuit that links the
neck, heart, lungs, and the abdomen to the brain.
What does the vagus nerve affect?
The vagus nerve has a number of different functions.
The four key functions of the vagus nerve are:
·
Sensory: From the
throat, heart, lungs, and abdomen.
·
Special
sensory:
Provides taste sensation behind the tongue.
·
Motor: Provides
movement functions for the muscles in the neck responsible for swallowing and
speech.
·
Parasympathetic: Responsible
for the digestive tract, respiration, and heart rate functioning.
Its functions can be broken down even further into
seven categories. One of these is balancing the nervous system.
The nervous system can be divided into two areas:
sympathetic and parasympathetic. The sympathetic side increases alertness,
energy, blood pressure, heart rate, and breathing rate.
The parasympathetic side, which the vagus nerve is
heavily involved in, decreases alertness, blood pressure, and heart rate, and
helps with calmness, relaxation, and digestion. As a result, the vagus nerve
also helps with defecation, urination, and sexual arousal.
Other vagus nerve effects include:
·
Communication
between the brain and the gut: The vagus nerve delivers information
from the gut to the brain.
·
Relaxation
with deep breathing: The vagus nerve communicates with the diaphragm.
With deep breaths, a person feels more relaxed.
·
Decreasing
inflammation:
The vagus nerve sends an anti-inflammatory signal to other parts of the body.
·
Lowering
the heart rate and blood pressure: If the vagus nerve is overactive, it
can lead to the heart being unable to pump enough blood around the body. In
some cases, excessive vagus nerve activity can cause loss of consciousness and
organ damage.
·
Fear
management:
The vagus nerve sends information from the gut to the brain, which is linked to
dealing with stress, anxiety, and fear - hence
the saying, "gut feeling." These signals help a person to recover
from stressful and scary situations.
Vagus nerve stimulation
Stimulation of the vagus nerve is a medical procedure
that is used to try to treat a variety of conditions. It can be done either
manually or through electrical pulses.
The effectiveness of vagus nerve stimulation has been
tested through clinical trials. Consequently, the United States Food and Drug
Administration (FDA) has approved its use to treat two
different conditions.
Epilepsy
In 1997, the FDA allowed the use of vagus nerve
stimulation for refractory epilepsy.
This involves a small, electrical device, similar to a
pacemaker, being placed in a person's chest. A thin wire known as a lead runs
from the device to the vagus nerve.
The device is placed in the body by surgery under
general anesthetic. It then sends electrical impulses at regular intervals,
throughout the day, to the brain via the vagus nerve to reduce the severity, or
even stop, seizures.
Vagus nerve stimulation for epilepsy may have some side effects including sore throat and difficulty swallowing.
Side effects of vagus nerve stimulation for epilepsy
include:
·
hoarseness
or changes in voice
·
shortness
of breath
·
coughing
·
slow
heart rate
·
difficulty
swallowing
·
stomach
discomfort or nausea
People using this form of treatment should always tell
their doctor if they are having any problems as there may be ways to reduce or
stop these.
Mental illness
In 2005, the FDA approved the use of vagus nerve
stimulation as a treatment for depression. It has also been found to help with
the following conditions:
·
rapid
cycling bipolar disorder
·
anxiety
disorders
Further research and considerations
With the vagus nerve having pathways to almost every
organ in the body, researchers are looking to see if stimulation can help other
conditions.
Studies suggest that stimulation of the vagus nerve may help to reduce symptoms of rheumatoid arthritis.
These conditions include:
·
rheumatoid
arthritis inflammation
·
inflammation from diabetes mellitus
·
intractable hiccups
·
abnormal
heart rhythm
·
inflammation
from Crohn's
disease
In the case of rheumatoid arthritis, which affects 1.3
million adults in the U.S., a study in 2016
showed that vagus nerve stimulation could help reduce symptoms. Individuals who
had failed to respond to other treatment reported significant improvements,
while no serious adverse side effects were noted.
This was considered a real breakthrough in how vagus
nerve stimulation might not only treat rheumatoid arthritis but other
inflammatory diseases, such as Crohn's, Parkinson's, and Alzheimer's.
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