Vagus nerve: what it is and what functions it has in the nervous system
The vagus nerve is the number 10 of the cranial nerves . Among other things, it is responsible for transmitting information related to sensory and muscular activity, as well as anatomical functions.
Next we will briefly see what the cranial nerves are, and later we define the vagus nerve.
- Related article: "Parts of the Nervous System: functions and anatomical structures"
The cranial nerves
The lower part of our brain is composed of a complex network of nerves that we know as "cranial nerves" or "cranial nerves". In total there are 12, they originate directly in our brain and they are distributed along different fibers by means of holes that are in the base of the skull towards the neck, the thorax and the abdomen.
Each of these nerves is composed of fibers that fulfill different functions and that arise from a specific part of the brain (may be at the base or stem). According to their location and the specific place from which they depart, cranial nerves are divided into subgroups :
- On the stem are pairs I and II.
- In the mesencephalon, pairs III and IV are found.
- On the bridge of Varolio are the V, VI, VII and VIII.
- Finally, in the spinal bulb are the IX, X, XI and XII.
At the same time, each of them has different names according to their origin, their activity, or the specific function that they comply In the following sections we will see how it is defined and what functions the vagus nerve has.
What is the vagus nerve?
The vagus nerve is one of the cranial nerves that is distinguished by having four nuclei and five different types of fiber. Specifically, it is the cranial pair number X and it is The most predominant neural effector of the parasympathetic nervous system , since it comprises 75% of all its nerve fibers (Czura & Tracey, 2007).
It is known as "vague" nerve to mention ramblings and rodeos. It is the nerve whose course is the longest of the cranial nerves, they extend and distribute widely below the level of the head.
It arises in the medulla oblongata or medulla oblongata, and advances towards the jugular foramen , passing between the glosso pharyngeal and spinal accessory nerves, and consists of two ganglia: one superior and one inferior.
Starting from the medulla oblongata and through the jugular foramen, the vagus nerve descends towards the thorax, crossing different nerves, veins and arteries. Both the left and the right part extend from the neck to the thorax; for this reason he is responsible for taking part of the parasympathetic fibers to the thoracic viscera.
The vagus nerve interacts especially with the immune system and the central nervous system and performs motor functions in the larynx, diaphragm, stomach, heart . It also has sensory functions in the ears, tongue and visceral organs such as the liver.
The damages of this nerve can cause dysphagia (swallowing problems), or an incomplete closure of the oropharynx and nasopharynx. On the other hand, pharmacological interventions on the vagus nerve can help control various pains , for example those that are caused by cancer and by tumors of the larynx or intrathoracic diseases.
- Maybe you're interested: "Parasympathetic nervous system: functions and travel"
Connection with other nerves
As we saw before, the vagus nerve connects with different nerves, that is, exchanges several of its fibers and functions. According to Barral, J-P. & Croibier, A. (2009), the nerves with which it connects are the following :
- Accessory nerve.
- Glossopharyngeal nerve.
- Facial nerve.
- Hypoglossal nerve.
- Sympathetic nerve
- The first two spinal nerves.
- Phrenic nerve.
Its 5 types of fibers and their functions
The nerve fibers, or nerves, are the extensions that connect the center of each nerve cell with the next. They transmit signals that are known as action potentials and they allow us to process the stimuli.
The latter are not the only types of fibers, there are also to connect and activate effector organs, muscle fibers or glands. According to Rea (2014), the vagus nerve has the following types of fibers.
1. Brachial motor fiber
Active and regulate the muscles of the pharynx and larynx .
2. Sensory visceral fiber
Responsible for transmitting information from a wide variety of organs , such as the heart and lungs, pharynx and larynx, and the upper part of the gastrointestinal tract.
3. Visceral motor fiber
It is responsible for carrying the parasympathetic fibers from the smooth muscle to the respiratory tract, the heart and the gastrointestinal tract .
4. Special sensory fiber
The vagus nerve transmits information necessary for taste of the palate and the epiglottis (the fibrous cartilage that closes the entrance of the larynx during swallowing)
5. General sensory fiber
This component allows the passage of information from parts of the ear and the dura within the posterior cranial fossa.
- Barral, J-P. (2009). Vagus nerve Manual Therapy for the Cranial Nerves. Elsevier: USA.
- Rea, P. (2014). Vagus Nerve Clinical Anatomy of the Cranial Nerves. Elsevier Academic Press: UK.
- Czura, C. (2007). Cholinergic Regulation of Inflammation. Psychoneuroimmunology (Fourth Edition). Elsevier Academic Press: USA.
- Waldman, S. (2007). Pain Management. Saunders: USA.