Vagus nerve: what is it and what are its functions in the nervous system?
One of the most important cranial nerves, belonging to the parasympathetic 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 see in a brief way what are the cranial nerves, and later we define the vagus nerve.
The cranial nerves
The lower part of our brain is composed of a complex network of nerves known as "cranial nerves" or "cranial nerves". In total there are 12 of them, they originate directly in our brain and are distributed along different fibers through holes at the base of the skull to the neck, thorax and abdomen.
Each of these nerves is composed of fibers that perform different functions and arise from a specific part of the brain (either in the base or in the stem). According to their location and the specific place from which they originate, the cranial nerves are divided into subgroups:
- On the stem are pairs I and II.
- In the midbrain are pairs III and IV.
- In the pons are V, VI, VII and VIII.
- Finally, in the medulla oblongata are IX, X, XI and XII.
In turn, each of them has different names according to their origin, their activity, or the specific function they perform. they fulfill. In the following sections we will see how the vagus nerve is defined and what functions it 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 fiber types. Specifically, it is the cranial nerve number X and it is the most predominant neural effector of the parasympathetic nervous system, comprising 75% of all its nerve fibers (Czura & Tracey, 2007).as it comprises 75% of all its nerve fibers (Czura & Tracey, 2007).
It is known as the "vagus" nerve to refer to digressions and detours. It is the nerve whose course is the longest of the cranial nerves, extending and distributing widely below the level of the head.
It arises in the medulla oblongata or medulla oblongata or medulla oblongata, and proceeds to the jugular foramen, passing between the accessory nerves gygomaticus and the medulla oblongata.It is composed of two ganglia: one superior and one inferior.
Starting from the medulla oblongata and passing through the jugular foramen, the vagus nerve descends towards the thorax, passing through different nerves, veins and arteries. Both its left and right parts extend into the neck up to the thorax; therefore it is responsible for carrying part of the parasympathetic fibers to the thoracic viscera.
The vagus nerve interacts especially with the immune system and the central nervous system, and has motor functions in the larynx, diaphragm and the central nervous system and has motor functions in the larynx, diaphragm, stomach, heart. It also has sensory functions in the ears, tongue and visceral organs such as the liver.
Damage to this nerve can cause dysphagia (swallowing problems), or incomplete closure of the oropharynx and nasopharynx. On the other hand, pharmacological interventions on the vagus nerve can help to control different painsfor example those caused by Cancer and by tumors of the larynx or intrathoracic diseases.
Connection with other nerves
As we saw before, the vagus nerve connects with different nerves, that is, it exchanges several of its fibers and functions. According to Barral, J-P. & Croibier, A. (2009), the nerves with which it connects are as follows:
- 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
Nerve fibers, or nerves, are the extensions that connect the center of each nerve cell to the next. They transmit signals that are known as action potentials and allow us to process stimuli.
The latter are not the only types of fibers, there are also those 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
Activates and regulates the muscles of the pharynx and larynx..
2. Visceral sensory fiber
In charge of transmitting information from a wide variety of organssuch 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 from smooth muscle to the respiratory tract, heart and gastrointestinal tract..
4. Special sensory fiber
The vagus nerve transmits information necessary for taste to the palate and 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 dura mater into the posterior cranial fossa.
Bibliographical references:
- 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.
(Updated at Apr 13 / 2024)