Vagus nerve: what is it 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’ll briefly consider what cranial nerves are, and then define the vagus nerve.

    The cranial pairs

    The lower part of our brain is made up of a complex network of nerves that we call “cranial nerves” or “cranial pairs”. In total there are 12, they come directly from our brain and are distributed along different fibers by means of holes which are at the base of the skull towards the neck, thorax and abdomen.

    Each of these nerves is made up of fibers that perform different functions and originate from a specific part of the brain (it can be at the base or in the stem). Depending on their location and the precise place from which they depart, cranial pairs are divided into subgroups:

    • On the rod are pairs I and II.
    • In the midbrain are pairs III and IV.
    • In the Varolio bridge, there are the V, VI, VII and VIII.
    • Finally, in the medulla oblongata are the IX, X, XI and XII.

    In turn, each has different names depending on its origin, activity or specific function that are compliant. In the following sections we will see how it is defined and what are the functions of the vagus nerve.

    What is the vagus nerve?

    The vagus nerve is one of the cranial nerves that is distinguished by its four nuclei and five different types of fibers. More precisely, it is the number of cranial pairs X and is the most predominant neural effector of the parasympathetic nervous system, As it comprises 75% of all its nerve fibers (Czura & Tracey, 2007).

    It is known as the “vagus” nerve to denote wanderings and funnels. It is the nerve the course is the longest of the cranial nerves, they extend and are distributed 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 pharyngeal accessory nerves and the shine of the spine, and consists of two ganglia: an upper and an inferior.

    Starting from the medulla oblongata and through the jugular foramen, the vagus nerve descends to the thorax, passing through various nerves, veins and arteries. Its two left and right bands extend inside the neck to the thorax; for this reason, it is responsible for transporting part of the parasympathetic fibers to the thoracic viscera.

    The vagus nerve interacts in particular with the immune system and the central nervous system and performs the motor functions of 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 buccopharynx and nasopharynx. On another side, pharmacological interventions on the vagus nerve can help control different pains, For example those caused by cancer and tumors of the larynx or intrathoracic diseases.

      Connection with other nerves

      As we saw earlier, the vagus nerve connects with different nerves, that is, it exchanges several of its fibers and functions. According to Barral, JP. And Croibier, A. (2009), the nerves it connects with are as follows:

      • Accessory nerves.
      • Glossopharyngeal nerves.
      • Facial nerves.
      • 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 called action potentials and allow us to process stimuli.

      These are not the only types of fibers, they are also available 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

      Activate 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 gastrointestinal tract.

      3. Visceral motor fiber

      It is responsible for the transport of parasympathetic fibers smooth muscle to the respiratory tract, heart and gastrointestinal tract.

      4. Special sensory fiber

      The vagus nerve transmits the information necessary for the taste of the palate and the epiglottis (the fibrous cartilage that closes the entrance to the larynx during swallowing)

      5. General sensory fiber

      This component allows the passage of information from parts of the ear and dura mater to the posterior cranial fossa.

      Bibliographical references:

      • Barral, JP. (2009). Vague nerves. Manual therapy of the cranial nerves. Elsevier: United States.
      • Rea, P. (2014). Nervi Vagus. Clinical anatomy of the cranial nerves. Elsevier Academic Press: United Kingdom.
      • Czura, C. (2007). Cholinergic regulation of inflammation. Psychoneuroimmunology (fourth edition). Elsevier Academic Press: United States.
      • Waldman, S. (2007). Pain management. Saunders: United States.

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