The Vagus nerve is the tenth cranial nerve located in the nervous system of mammals, and this includes both humans and animals, such as dogs and cats. The animal body is a living wonder. It is extremely clever, yet the nerves more especially, the vagus nerve is frequently disregarded, despite the crucial role they play in preserving health (3).
Anatomy Of The Vagus Nerve In Animals
Of the twelve cranial nerves, the vagus nerve is the longest, the paired nerves that emerge from the brainstem and mostly supply cranial regions. The tenth cranial nerve is unique among the others in that the majority of its domain is located outside the head. In animals, the vagus nerve still maintains its position as the tenth cranial nerve as in other mammals (4).
The peripheral nervous system (PNS) and the central nervous system (CNS) both have several components that make up the autonomic nervous system (ANS) (PNS).
The general visceral afferent (GVA) system and the general visceral efferent (GVE) system, which includes parasympathetic and sympathetic components, are their principal afferents and efferents, respectively.
Parts of cranial nerves III, VII, IX, and X include parasympathetic preganglionic axons that exit the brainstem. While the vagus nerve (X) distributes autonomic axons to the cervical, thoracic, and abdominal viscera as far caudally as the left colic flexure, the axons of nerves III, VII, and IX are distributed to the head region.
A considerable portion of the general visceral afferent, GVA axons, and a lesser portion of preganglionic parasympathetic general visceral efferent, GVE axons are among the vagus nerve’s functional components. More than 80% of the “C” axons are claimed to be present in the cervical section of the vagus nerve, with the remaining 20% being myelinated.
The parasympathetic nucleus of the vagus nerve is thought to be the source of the bulk of the “C” axons’ afferent parasympathetic fibers and the remainder of their efferent parasympathetic fibers (nucleus parasympathetic vagi). The paired nucleus is situated ventral to the floor of the fourth ventricle, in the dorsal region of the caudal medulla oblongata, and lateral to the hypoglossal nucleus.
Branches Of The Vagus Nerve In Animals
The vagus nerve gives off four main branches namely: The pharyngeal branches, recurrent laryngeal nerves, superior laryngeal nerves, and superior cardiac nerves (5).
Through the rootlets of cranial nerves IX and XI, the vagal rootlets exit the brain along the dorsolateral sulcus of the medulla oblongata. Certain species have described some vagal axons as being a part of the cranial root of the accessory nerve due to their close relationship with those of the accessory (XI) nerve over a very short distance.
The little proximal vagal ganglion is situated a few millimeters distal to the vagus origin. It is situated at the tympanooccipital fissure level and is made up of unipolar general somatic afferent neurons, whose axons are disseminated along the vagus auricular branch.
It has been demonstrated that this branch is disseminated in part by branches of the seventh cranial nerve, which leaves the vagus at around the level of the proximal vagal ganglion. Additionally, some of the branches in the canine tongue contain cell bodies in the proximal ganglia of the vagus.
Between the proximal and distal vagal ganglia, the vagus gives out its pharyngeal branch. The unipolar GVA neurons that make up the majority of the later ganglia are distributed peripherally throughout the viscera.
At the level of the distal ganglion, the vagus nerve is exited via the cranial laryngeal nerve. The distal vagal ganglion is medial and rostral to the sympathetic cranial cervical ganglion. The two ganglia’s epineurial sheaths may be distinct or exhibit varying degrees of fusion. It is possible to see the branches that emerge from the vagus by carefully dissecting the vagus and its ganglia and peeling back the epineurial sheath. A short, unidentified bundle of vagal axons that bypasses the distal ganglia can be observed in certain cases.
The sympathetic trunk and the vagus merge just distal to the distal vagal ganglion, and they are sheathed together along the whole cervical region. Where it is tightly attached to the vagus, the sympathetic trunk may remain rounded (in cross-section) or may take on a crescent shape. However, in certain specimens, it is simple to distinguish between the two by dissection.
The right vagus nerve travels ventral to the right subclavian artery and continues caudally along the lateral side of the trachea after typically separating from the sympathetic trunk a short distance cranial to the level of the middle cervical ganglion. The ansa subclavia may be briefly and closely connected to the vagus at the level of the subclavian artery.
The middle cervical ganglion or the ansa subclavia may also send branches to the vagus and recurrent laryngeal nerves in this area. The vagus throws out two or more fine cardiac branches that are distal to the origin of the recurrent laryngeal nerve. The pretracheal plexus is mostly served by the cranial branches. The right atrium’s dorsal wall is supplied by the caudal cardiac branches (1).
The Health Of The Vagus Nerve In Animals
The vagus nerve, which is the 10th cranial nerve, is both the key and the remedy to the stress-imbalance problem that animals, particularly working dogs, experience.
The longest nerve in the body, it is also. It descends to the distal large intestine from the brain. It controls everything from digestion to blood pressure to heart rhythm to breathing pace. Even hearing, vision, and brain function are affected by it (among other things) (2).
The vagus nerve, which travels straight from the gut to the brain, and the intimate connection between them influence how the brain regulates emotions and moods as well as physical, mental, and spiritual health.
Diet and way of living influence how the body reacts. The animal’s general health and gut health are very essential. Serotonin, the chemical responsible for tranquility and contentment, is created and stored in the stomach 95% of the time, where it is then transported to the brain via the vagus nerve. The microorganisms in the stomach assist drive serotonin synthesis, and 60% of the serotonin generated in the gut is directly derived from food digestion. Poor lifestyle choices and improper kinds of food are bad for the vagus nerve’s health.
The body can withstand a certain amount of stress in the short term, but sustained stress or long-term stressful conditions place an enormous load on all of the body’s systems and eventually cause serious health problems including cardiovascular disease.
The animals continue in a cycle of fight or flight with little to no time for rest and digesting unless nutrition, lifestyle, and level of stress are addressed, cleaned up, and appropriately handled. The development of allergies, states of illness and disease, the body’s capacity to withstand pain, and poorer emotional states like despair, anxiety, wrath, etc. are all linked to poor gut health, according to scientists (3).
Vagus Nerve Damage In Animals
The vagus nerve can be affected by a wide range of conditions, and difficulties with it might result in other health problems. Each animal can exhibit distinct symptoms. There are many common symptoms among a variety of diseases and illnesses, but one thing they all share is inflammation, which occurs when the body is out of balance with its natural environment and away from a healthy pH level. Symptoms may also be the cause of some other disorders.
This is not an exhaustive list; it is merely a wide one. Studies on vagus nerve damage in animals and the causes are scarce and frequently biased, thus much more investigation is required. However, you should consult your holistic veterinarian to ensure the health difficulties you are experiencing are unrelated to the damage to your gut and vagus nerve before undergoing any major treatment or procedures.
The common areas of vagus nerve disorders in animals are:
Gut health
Gut health can affect how well the vagus nerve responds to inflammation and immunological response, which can lead to immune imbalances and auto-immune problems.
Long-term digestive problems can harm the vagus nerve’s full functionality and the body’s capacity to correctly absorb nutrients, leading to diseases like IBS or malnutrition, among other things.
Brain Health
Damage to the vagus nerve can cause issues with mental health, cognitive abilities, emotions, and behavior, including anxiety, fear, compulsive disorders, anger, and house urinating, among others. Sensory information is impacted by the gut-brain link.
A signal either through the sympathetic nervous system (freeze, fight, or flight) or the parasympathetic nervous system is triggered by about 70% of sensory information being carried to the brain through the vagus nerve (rest, digest). The vagus nerve is thought to play a role in a variety of functions, including memory, focus, mood swings, depression, learning ability, and so forth.
Musculoskeletal
difficulties with posture, gait, and movement. A leaky stomach can cause particles to enter the vagus nerve, which then travels to the brain and affects neurotransmitters that influence and limit movement. Some neurological conditions and illnesses are caused by leaks from the gut into the brain via the vagus nerve.
Reflexes
The transmission of messages and a significant role in motor processes are both performed by the vagus nerve. The normal or abnormal firing of impulses along nerve fibers for reflexes and muscular activities depends on the state of the gut-brain axis.
For instance, vagus nerve damage may cause alterations in your pet’s natural reflexes, such as recurrent coughing, gagging, and difficulty swallowing. Problems with motor coordination might also affect your pet’s ability to perceive the world around it visually and audibly.
Cardiovascular health
The vagus nerve and the gut-brain link control how the heart rate reacts at any particular time and any variation in heart rate will affect how the blood reacts to the situation, such as high or low blood pressure, and how long the body stays in either state (3).
Vagal Nerve Activation In Animals
The parasympathetic nervous system, often known as the rest and digest system, is activated when the vagus nerve is stimulated, while the flight or fight reaction is deactivated (also called the sympathetic nervous system). This makes it possible to unwind completely.
An animal should ideally only enter fight-or-flight mode occasionally. (A gazelle being pursued by a lion is an extremely uncommon occurrence!) And as soon as it did activate, the animal would immediately start shaking all over. By doing so, it would be able to discharge the stress hormones that had accumulated during the chase. In the end, this is what enables the animal to reset, returning to its tranquil, at-ease state.
After a stressful experience like this, having a high vagal tone enables fast relaxation (2).
Stimulation of vagus nerve in animals
The following are the various ways to stimulate the vagus nerve in animals:
- For both physical and emotional wellness, proper movement and exercise are crucial. Not only does it improve cardiovascular health, but it also oxygenates the blood, aiding in the removal of stagnation, and stimulates the lymphatic system to remove toxins from the body.
- Reduce environmental sensory overload. putting all electronics, wifi, and modems off at night. Electric-magnetic frequencies from electronics, which constantly bombard the body and have a significant negative influence on health and emotional well-being, must be reduced more than ever. This is becoming more evident in areas where 5G towers have been turned on, where there are growing pockets of ill animals and mortality problems that present with radiation harm.
- Consider acupuncture as a tool to assist with vagus nerve stimulation and nervous system rebalancing.
- Stop using chemical flea treatments. They are all loaded with neurotoxins and harmful to an animal’s short- and long-term health because they alter the gut’s flora, which in turn affects the vagus nerve and all other organs. Additionally connected to vaccination harm and the beginning of neurological disorders in animals is vagus nerve injury.
- Add more enjoyable play and cerebral stimulation. This involves the mind and body equally and can lessen or get rid of physical stress (3).
References
- https://veteriankey.com/the-autonomic-nervous-system-2/
- https://workingdoghq.com/k9-vagus-nerve/#:~:text=The%20vagus%20nerve%20is%20the,to%20the%20distal%20large%20intestine.
- https://authenticapets.com/en/blog/vagus-nerve-in-cats-and-dogs
- https://pubmed.ncbi.nlm.nih.gov/35950655/
- https://www.ncbi.nlm.nih.gov/books/NBK537171/#:~:text=The%20vagus%20nerve%20has%20branches,nerves%2C%20and%20superior%20cardiac%20nerves.
