The cranial nerves are the nerves found in the human body; They are classified by numbers (and also by names), which correspond to the order in which they are located. They are responsible for various functions related to the control of muscles and some glands, mainly sensory.
Among the cranial nerves, the number X stands out for its long extension, in addition to having great complexity, being responsible for many functions throughout the organism. This nerve is also known as the vagus nerve, however its name does not refer to the fact that it has few functions (quite the opposite), but rather to the fact that it is considered a wandering nerve.
What is the vagus nerve?
The vagus nerve or cranial nerve It is one of the most important parts of the parasympathetic nervous system.
Its classification as Its classification as lazy refers to its wandering quality that leaves the brain and descends to the abdominal area.
Following (2019), the vagus nerve has 4 nuclei, each of them in charge of specific tasks, where its dorsal nucleus is responsible for the parasympathetic innervation of the intestinal area, while the nucleus ambiguus goes directly to the heart with both parasympathetic fibers. as motor efferents.
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On the other hand, there is the solitary nucleus, whose function is to receive visceral and gustatory fibers, and finally, the spinal trigeminal nucleus, whose function is purely sensory.
Origin of the vagus nerve
The vagus nerve has 2 origins, a real one, which is where it is formed, and an apparent one, which is the place in the brain through which the output of its fibers is perceived.
Its apparent origin is found in the medulla oblongata, right at the root of the spinal nerve, close to the exit of the glossopharyngeal cranial nerve, but its sensory fibers come from the jugular and plexiform ganglia, while the motor fibers come from the nucleus ambiguus, near the glossopharyngeal nerve, and its vegetative fibers arise from the dorsal nucleus.
Its innervations and fibers
The vagus nerve, as we have already mentioned, is responsible for various functions in the body depending on its field of innervation, which is divided into:
- General sensory afferent.
- General visceral afferent.
- special afferent.
- General visceral efferent.
Each of them is responsible for collecting and carrying information to and from the brain to control various functions.
On the other hand, it has 5 different types of fibers that have specific functions; these are:
1. Brachial motor fiber. It is the part of the vagus nerve that is responsible for the motor function of the larynx and pharynx, being responsible for their regulation and activation.
2. Sensory visceral fiber. It is one of the most complex because its function covers multiple organs of the body in the thoracoabdominal part, being responsible for carrying information to and from the larynx, pharynx, lungs and heart, and is even responsible for part of the gastrointestinal tract. .
3. Visceral motor fiber. It is responsible for information from the smooth muscle, it is responsible for the heart, gastrointestinal tract and respiratory tract.
4. Special sensory fiber. Fundamental for the swallowing and feeding process, as it controls the epiglottis, which is the part of the larynx that opens and closes in the swallowing process, it also plays a very important role in the reception of sensory information on the palate that allows us to feel taste. of food.
5. General sensory fiber. It collects and carries all the information from the posterior cranial fossa, specifically in the dura mater, in addition to being responsible for the passage of information from some parts of the ear.
Vagus nerve function
The vagus nerve is essential for human beings, as it is responsible for various functions fundamental to life, ranging from the control of various organs to the collection of sensory stimuli. Thanks to this nerve, the heart rate is controlled, and on the other hand, the nerve is also responsible for the motor activity of breathing and the digestive process.
One of its functions is to determine when the activation of the digestive system is necessary for the processing of food, and also when to stop it so that it rests when it is not necessary, being responsible for the function of the movements of both the intestine and the esophagus.
Another of its functions is swallowing; It is responsible for the cough and vomiting reflex, but also, because it is a nerve with sensory qualities, it helps with the perception of gustatory stimuli, helping to identify different flavors.
References:
- Carlson, N. R. (2005). Behavioral physiology. Madrid: Pearson Education.
- Crossman, A.R. and Neary, D. (2019). Neuroanatomy. Barcelona: Elsevier.