Introduction to Vagus Nerve
The peripheral nervous system (PNS) of the animal body has two parts- the somatic nervous system and the autonomic nervous system. The autonomic nervous system controls the function of the internal organs of the animal body. The ANS completes its operation through the sympathetic nervous system and the parasympathetic nervous system. The parasympathetic nervous system regulates body functions. The vagus nerve is one of the most important components of the parasympathetic nervous system. It is the longest pair of the 12 pairs of cranial nerves. It consists of the left and right vagus nerves. It connects the brain with the gastrointestinal tract. It sends information to the brain about the states of the internal organs through different fibers. The vagus nerve affects heart rate, digestion, immune response, mood, etc. In this article, we will discuss vagus nerve function, vagus nerve anatomy, vagus nerve pathway, vagus nerve disorders, vagus nerve stimulation in detail.
Anatomy Of Vagus Nerve
The vagus nerve is the longest cranial nerve of the parasympathetic nervous system. It is structured with a pair of nerves- the left vagus nerve and the right vagus nerve. This nerve runs from the brain to the colon. It is also called the ‘wanderer nerve’ for its long extension in the animal body. It carries a massive range of signals from the brain to the internal organs and the digestive system and vice versa. This nerve exits the cranium via the jugular foramen originating from the medulla of the brainstem. It passes into the carotid sheath in the neck. The nerve is divided into the left and right parts at the base of the neck. Two parts of the nerve have different vagus nerve pathways from the neck. The right path creates the posterior vagal trunk and the left part forms the anterior vagal trunk in the thorax. Both the vagal trunks end in the abdomen. You can go through the vagus nerve anatomy PDF to learn the diagram.
Vagus Nerve Function
The vagus nerve plays a vital role in the autonomic nervous system. It has several different functions in the animal body. The vagus nerve affects some important internal body processes such as heart rate, digestive system, immune response, mood, etc. The main four functions of this nerve are sensory, special sensory, motor, and parasympathetic. The sensory functions operate on the throat, heart, lungs, and abdomen. The special sensory function provides taste sensations behind the tongue. The motor functions provide movement functions for the muscles in the neck. The parasympathetic functions are responsible for the respiration and digestive tract. Some other functions are communication between the brain and the gut, relaxation with deep breathing, lowering blood pressure, decreasing inflammation, fear management, etc. Apart from these, the vagus nerve function in the heart is also crucial for the animal body.
(Image Will be Updated Soon)
Vagus Nerve Location
As the Vagus nerve is the longest of all cranial nerves, it is connected from the brain to the bottom part of the body. The Vagus nerve location can be explained systematically. The vagus starts from the brain and moves towards the face and reaches the abdomen through the thorax. The Vagus nerve is quite a complex nerve that has parasympathetic fibers as well as two branches of sensory ganglia.
One is superior sensory ganglion which moves through the skin and reaches the ear's concha. Again, the inferior vagus nerve ganglion is divided into two branches. The pharyngeal nerve and the laryngeal nerve along with esophageal, and pulmonary branches. Each branch functions for different parts of our bodies. These nerves send signals to all parts of the body which include the stomach, cardiac muscles, pancreas, etc.
Functions of Vagus Nerve
The vagus nerve is the 10th cranial nerve in the body and has different types of functions. They are as follows.
Sensory Functions:-
The sensory functions of the vagus are divided into two different components.
One is somatic components which refer to the sensations felt by the brain from the skin as well as muscles.
If the sensations felt by the brain are due to the organs of the body, then those components are known as visceral components.
Besides these components, the sensory functions performed by the Vagus nerve are as follows-
They help to provide the information from the brain to the skin, middle parts of the throat, and external parts of the ear.
The larynx, heart, esophagus, trachea, lungs, and most of the digestive tract receive visceral information through the brain.
Also contributes to providing the information of taste at the bottom part of the tongue. This part is also known as the root part of the tongue. This function is nothing but a special sensory function of the Vagus nerve.
(Image will be Uploaded Soon)
Motor Functions
The motor functions of the Vagus nerves majorly include the transferring of information for the larynx and pharynx.
Provides information and stimulates a muscle of the fleshy part around the tongue and mouth. These parts include the larynx, firings, and a soft palate.
It also has a major part in reducing the resting heart rate.
A motor function that helps to contract the involuntary muscles of the stomach, intestine and helps to move the food through a tract.
These are the different functions performed by the vagus nerve present in the body. Also, some cardiac functions were known as parasympathetic functions of the Vagus nerve. The vagus nerves supply all types of information to various parts of the body. Every function of the vagus nerves has its cell bodies, unique name, etc.
Bottom Line
Hence, the vagus nerve helps to supply various information to various parts of the brain and vice versa. This is the 10th cranial nerve present in the body. The Roman number is used to represent its notation. One should keep all the cranial nerves properly and healthy. Especially the vagus should be healthy as it performs various functions.
Vagus Nerve Disorders
There are several damages of the vagus nerve that are noticeable in the animal body. The potential symptoms of vagus nerve damage are difficulty in speaking, change of voice, loss of the gag reflex, difficulty swallowing, slow heart rate, low blood pressure, nausea or vomiting, changes in the digestive process, abdominal pain, depression and anxiety, heart diseases, etc. Two common vagus nerve disorders are gastroparesis and vasovagal syncope. The symptoms of gastroparesis are nausea or vomiting, acid reflux, loss of appetite, abdominal pain, fluctuations in blood sugar and blood pressure, unexplained weight loss, etc. The symptoms of vasovagal syncope are warmth, tunnel vision, nausea, low blood pressure, slow or irregular heartbeat ringing in the ears, excessive sweating, etc.
Vagus Nerve Stimulation
The treatment process of vagus nerve diseases is called vagus nerve stimulation. It is a medical process that is done manually or through electrical pulses. Generally, it is used for the treatment of mental illness and epilepsy. The simulation process is used in some specific mental conditions such as bipolar disorder, Alzheimer’s disease, anxiety disorders, etc. For epilepsy, a small electrical device is used for stimulation. A thin wire from the device is connected to the vagus nerve in this process. The side effects of this treatment process are hoarseness or changes in voice, shortness of breath, sore throat, coughing, difficulty in swallowing, slow heart rate, stomach discomfort or nausea, etc.
FAQs on Vagus Nerve
1. What is the Vagus Nerve, and why is it often called the 'wandering nerve'?
The Vagus Nerve, also known as cranial nerve X, is the longest and most complex of the twelve cranial nerves. It is called the 'wandering nerve' (from the Latin word 'vagus' meaning wanderer) because it originates in the brainstem and travels extensively throughout the body, branching out to innervate vital organs in the neck, chest, and abdomen, unlike other cranial nerves which are mostly confined to the head and neck region.
2. What are the primary functions of the Vagus Nerve in the human body?
The Vagus Nerve has several critical functions as it is a mixed nerve containing both sensory and motor fibres. Its primary roles include:
- Parasympathetic Control: It is the main component of the parasympathetic nervous system, responsible for the body's 'rest and digest' functions. It helps slow the heart rate, stimulate digestion, and control involuntary muscle movements in the pharynx, larynx, and digestive tract.
- Sensory Function: It transmits sensory information from the organs in the chest and abdomen (like the heart, lungs, and gut) back to the brain.
- Motor Function: It controls muscles in the throat and larynx, which are essential for swallowing and speaking.
3. What are the common signs and symptoms of vagus nerve dysfunction?
Damage or dysfunction of the vagus nerve can manifest in various ways depending on the affected branch. Common symptoms include difficulty swallowing (dysphagia), a hoarse or altered voice, loss of the gag reflex, irregular heart rate (arrhythmia), low blood pressure, nausea, vomiting, abdominal bloating, and acid reflux. In some cases, it can also contribute to mood disorders like anxiety and depression due to its role in the gut-brain axis.
4. How is the Vagus Nerve (Cranial Nerve X) different from other cranial nerves?
The main difference lies in its extensive distribution. While most cranial nerves (I-XII) provide sensory and motor functions primarily to structures within the head and neck, the Vagus Nerve is unique because it extends far beyond this region. It is the only cranial nerve that innervates thoracic and abdominal organs, playing a crucial role in regulating core bodily functions like heart rate, respiration, and digestion, which sets it apart from the more localised functions of nerves like the optic (II) or facial (VII) nerves.
5. Why is the Vagus Nerve considered a crucial component of the 'gut-brain axis'?
The Vagus Nerve forms the primary physical connection in the gut-brain axis, acting as a two-way communication highway. It sends signals from the gut's environment (e.g., presence of nutrients, state of inflammation) to the brain, influencing mood, stress, and behaviour. Conversely, it sends signals from the brain to the gut, controlling digestion, gut motility, and the release of digestive enzymes. This bidirectional link is vital for maintaining homeostasis and illustrates how our digestive health can directly impact our mental state.
6. How can damage to the vagus nerve lead to a condition like gastroparesis?
Gastroparesis is a condition where the stomach cannot empty itself of food in a normal fashion. The vagus nerve is responsible for stimulating the smooth muscles of the stomach to contract and push food into the small intestine. If the vagus nerve is damaged, these signals are impaired or lost. As a result, the stomach muscles do not contract properly, leading to delayed gastric emptying. Food remains in the stomach for longer than it should, causing symptoms like nausea, vomiting, bloating, and early satiety.
7. What is Vagus Nerve Stimulation (VNS) and what is its main biological purpose?
Vagus Nerve Stimulation (VNS) is a medical treatment that involves sending mild electrical pulses to the vagus nerve. Its biological purpose is to modulate the nerve's activity to influence brain function and autonomic processes. By stimulating the nerve, VNS can help regulate the release of neurotransmitters like serotonin and norepinephrine in the brain, which is why it is used to treat conditions like epilepsy and treatment-resistant depression. It essentially 'resets' or normalises the electrical and chemical signaling pathways controlled by the vagus nerve.
