The vagus nerve, also known as a pneumogastric nerve, is a nerve that travels from the brain to the abdomen, and along its path, gives rise to several branches that innervate several cervical, thoracic and abdominal organs, with sensory and motor functions, being important for the maintenance of vital functions like regulation of the heart and arterial frequency, for example.
The pair of vague nerves, located on either side of the body, are the 10th pair of a total of 12 cranial nerves that connect the brain to the body. As the cranial nerves are termed as Roman numerals, the vagus nerve is also called the X pair, and is considered the longest of the cranial nerves.
Certain stimuli to the vagus nerve, caused by anxiety, fear, pain, temperature changes or simply by standing for a long time, can cause the so-called vasovagal syncope, in which the person can have an intense dizziness or faint, because this nerve can cause a drop in heart rate and blood pressure. Understand vasovagal syncope and how to treat it.
Anatomy of the vagus nerve
The vagus nerve is the largest cranial nerve and originates from the back of the spinal bulb, a brain structure that connects the brain to the spinal cord, and leaves the skull through an opening called the jugular foramen, down the neck and thorax until it ends in the stomach.
During the course of the vagus nerve, it innervates the pharynx, larynx, heart and other organs, through which the brain perceives how these organs are and regulates several of their functions.
Main functions
Some of the main functions of the vagus nerve include:
- Reflexes of cough, swallowing and vomiting;
- Contraction of the vocal chords for the production of the voice;
- Control of contraction of the heart;
- Decreased heart rate;
- Respiratory movements and bronchial constriction;
- Coordination of movements of the esophagus and intestine, and increase of gastric secretion;
- Production of sweat.
In addition, the vagus nerve divides some of its functions with the glossopharyngeal nerve (IX pair), especially in the region of the neck, being responsible for the gustatory sensation, where the vagus nerve is more related to the sour and the glossopharyngeal with the bitter taste.
Changes in the vagus nerve
A paralysis of the vagus nerve may cause difficulty in swallowing, hoarseness, difficulty speaking, contractions in the pharynx and larynx muscles, and changes in blood pressure and heart rate. This paralysis can occur due to trauma, injury to surgeries, compression by tumors or certain neurological syndromes.
In addition, there are situations that cause excessive stimulation of the vagus nerve, generating a situation called vagal syncope or fainting. It usually occurs in young individuals and is due to the reduction of heart rate and blood pressure due to lack of oxygen in the brain, causing fainting. See what to do in case of fainting.
Vagal syncope may be caused by:
- Heat exposure;
- Strong emotions, like anger;
- Persist long standing;
- Temperature changes;
- Swallowing very large foods;
- Being at an elevated altitude;
- Feeling hunger, pain, or other unpleasant experiences.
Stimulation of the vagus nerve can also be done through a massage in the lateral region of the neck. Sometimes the vagal maneuver is made by the doctors in case of emergency to regularize the cardiac arrhythmia.
