In this in-depth look at the parasympathetic nervous system, we'll explore everything you need to know about what it does, its components (including the vagus nerve), and how it can improve your health. We'll cover everything you need to know about this powerful system, from the basics of how the parasympathetic nervous system works to specialized therapies like vagus nerve stimulation.
The Nervous System: Overview
Before we look specifically at the parasympathetic nervous system, let's start at the beginning and consider the basics of how the nervous system works.
The nervous system comprises two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS). Your CNS includes your brain and spinal cord, while your PNS consists of all other nerves throughout the body.
The Central Nervous System
We know this system includes your brain and spinal cord, but we want to break it down even further. The brain controls the entire body, and it's divided into three main parts - the forebrain, midbrain, and hindbrain.
The forebrain
You might think of this as the "thinking center" - it's responsible for higher-level thinking, including cognition, language, and memory. It also plays a vital role in homeostasis, or the body's ability to maintain a balanced and healthy internal environment. This includes everything from hormone production to blood pressure and body temperature.
The midbrain
This part of the brain helps us process what we see and hear. It's also crucial in controlling motor skills, eye movements, and auditory functions. Notably, it's also what connects our brain to our spinal cord.
The hindbrain
Lastly, the hindbrain is the portion of the brain that controls essential life functions like breathing, heart rate, and digestion. It's also involved in reflexive movements - things that happen without conscious thought or intention, like blinking when something comes too close to your eyes. On that note, it's also responsible for our involuntary reflexes, like sneezing.
Peripheral Nervous System: Components
The second major component of your nervous system is the PNS. This consists of all other nerves and can be divided into two main sections - the somatic nervous system (SNS) and autonomic nervous system (ANS).
However, before we get into those systems, let's take a closer look at general nerve anatomy.
Basic Nerve Anatomy
Think of your nerves as highways that carry messages to and from your brain. They consist of bundles of nerve fibers, which are a type of cells called neurons that transmit electrical signals. These neurons have five main parts: axons, dendrites, endoneurium, perineurium, and epineurium.
Axons
These are the longest part of the neuron and act as cables to transmit electrical signals. In addition, they have a protective covering called myelin that helps ensure the signal is sent quickly while staying safe from interference.
Dendrites
These branch out from the axon and help receive information from other cells.
Endoneurium
As explained in this 2009 report, the endoneurium is "the intrafascicular connective tissue. It is composed of several nerve fibers making up a primary fascicle. Glial cells, to which they are attached, provide each nerve with additional reinforcement."
Perineurium
The perineurium acts as a barrier between your endoneurium and the extrafascicular tissues.
Epineurium
Finally, the epineurium is the outermost layer of connective tissue that surrounds all the other layers of neurons. It helps keep everything in place and prevents any damage from occurring to the inner layers of neurons.
Types of Nerves
There are also two primary nerve types we should also discuss: motor nerves and sensory nerves.
Motor nerves
These nerves carry signals from your brain to your muscles and other organs, and they're responsible for things like movement and regulation. An example of your motor nerves in action would be when you walk - your brain sends a signal to your legs and feet, telling them to move.
Sensory nerves
On the flip side, sensory nerves transport information from your body's senses (like sight or touch) back to the brain. This helps you sense and interpret what's going on around you. For example, when you touch something hot, these nerves send a message to your brain so you can immediately pull away and avoid getting burned.
Now that we've gone over some of the basic anatomy, let's examine the two main sections of the PNS in closer detail.
Somatic nervous system (SNS)
Also known as our voluntary nervous system, this is the part of our nervous system responsible for voluntary movements and sensations. It's composed of sensory neurons that send signals from our skin, muscles, and joints to our brain and motor neurons that transmit signals from our brain to those same parts of our body.
Autonomic nervous system (ANS)
This is our involuntary nervous system, meaning it's responsible for things that happen without conscious thought or intention. It comprises three parts - the sympathetic, parasympathetic, and enteric nervous systems.
For our purposes today, we'll explore the parasympathetic nervous system in the most detail because it is home to your vagus nerve.
First, however, we should also discuss the sympathetic and enteric nervous systems to understand better how they work together.
Sympathetic nervous system
When we're in a stressful or dangerous situation, our sympathetic nervous system is the one that kicks into action. It's responsible for initiating our "fight or flight" response, which helps us quickly and efficiently respond to danger.
For example, suppose you hear a loud noise behind you. In that case, your body will immediately release adrenaline and other hormones that prepare you to either stand your ground or run away as fast as possible.
Some of the functions this component is in charge of include increasing our heart rate, constricting our blood vessels, and raising our blood pressure. This helps us get the energy we need for whatever action we take next - fleeing or fighting.
Enteric nervous system
This part of the ANS is primarily responsible for controlling digestion and other functions related to the gastrointestinal tract. It's made up of layers of neurons that line your digestive organs, such as your stomach, small intestine, and colon. Some of its primary functions include breaking down food for nutrient absorption and regulating hormones like insulin and glucagon that help control your blood sugar levels.
This system modulates immune and endocrine functions, which means it helps your body respond to stress, infection, and other threats. It also plays a role in regulating our appetite and satiety (feeling full after eating).
Together, the sympathetic, parasympathetic, and enteric nervous systems work to maintain balance in your body. This is known as homeostasis - a state of equilibrium that allows your body to perform optimally regardless of external conditions it encounters.
Parasympathetic Nervous System
Now let's discuss the parasympathetic nervous system. Again, this is where our vagus nerve lives. With an overview of the nervous system as a whole, we're ready to understand the role your parasympathetic nervous system plays within it.
The parasympathetic nervous system is responsible for calming our body down when it's in a "fight or flight" state. It acts as the opposite of the sympathetic nervous system, helping us relax and restore our energy levels after a stressful situation. This part of the ANS also plays an important role in keeping other bodily functions running smoothly, such as digestion, elimination, and mental clarity.
Some of its primary functions include stimulating digestive secretions (including saliva), slowing down the heart rate, dilating blood vessels, increasing motility (movement) in the gastrointestinal tract, and modulating hormones like insulin and glucagon. It can even help regulate emotions by sending calming signals from your brain to your body. But, as you can see, many of these functions counter the functions of the sympathetic nervous system.
By engaging with the parasympathetic nervous system, you can tap into its power to help reduce stress and improve your overall health. One of the most effective ways to do this is through vagus nerve stimulation (VNS). We'll discuss VNS in a moment, but let's first discuss some other things you should know about the vagus nerve and the other 11 cranial nerves.
12 Cranial Nerves
Your body has 12 cranial nerves, and the vagus nerve is the longest.
Here's a quick look at each of the 12 cranial nerves:
Olfactory nerve
This is your smell nerve. It transmits signals from your nose to your brain, allowing you to detect smells.
Optic nerve
This is your vision nerve. It helps transmit light and color signals from the eye to the brain, so you can see.
Oculomotor nerve
This nerve helps control the movement of your eyes in various directions.
Trochlear nerve
Your trochlear nerve is responsible for controlling the rotation of our eyes in different directions with the superior oblique eye muscles.
Trigeminal nerve
The trigeminal nerve serves multiple purposes, including helping us sense to touch on our face, as well as helping us control jaw movements.
Abducens nerve
This one helps control eyeball movement away from the midline of our head.
Facial nerve
Your facial nerve has sensory AND motor functions. On the sensory side, for example, it helps transmit the taste sensation from your tongue to your brain. On the motor side, it helps control facial expressions and movements.
Vestibulocochlear nerve
This one has two parts: vestibular and cochlear. The vestibular part helps you maintain balance, and the cochlear portion allows us to hear.
Glossopharyngeal nerve
The glossopharyngeal nerve transmits signals for taste (on the back of our tongue) as well as helps with swallowing reflexes.
Accessory nerve
This nerve combines with our vagus nerve (we'll come back to this later in this post), and it also helps control the muscles of our neck and shoulders.
Hypoglossal nerve
The hypoglossal nerve helps control tongue movement, including when we speak or swallow.
Vagus nerve
And now, finally, we come back to the vagus nerve. This is the longest and most complex of the cranial nerves, running all the way from your brain stem down to your abdomen. It plays a role in many different bodily functions, including moving food through our digestive tract, controlling blood pressure and heart rate, regulating breathing, and calming inflammation. It's also vital in maintaining healthy gut flora and keeping our immune system balanced. Finally, it helps us regulate emotions like stress so we can stay calm even when faced with challenging events.
Because of its incredible number of functions, the vagus nerve is sometimes referred to as our "wandering nerve." It's an essential part of the parasympathetic nervous system and directly impacts our overall health. With that in mind, it's no surprise that so many people are eager to stimulate this nerve and harness its potential benefits.
Vagus Nerve Stimulation (VNS)
The term "vagus nerve stimulation" is an umbrella term that can refer to various methods of stimulating the vagus nerve. For example, there is surgical VNS, transcutaneous vagus nerve stimulation (including Xen by Neuvana), and other non-invasive VNS methods, like cold exposure, yoga, and gargling.
Benefits of Vagus Nerve Stimulation
Before we detail the different methods of vagus nerve stimulation, let's first look at the wellness benefits of employing these methods.
Could lower inflammation
One of the main benefits of vagus nerve stimulation is that it can help lower inflammation in the body. This can reduce the risk of chronic conditions like heart disease, stroke, and even cancer. As such, it's a great way to reduce your overall risk of developing these conditions.
Could improve digestion
The vagus nerve plays an essential role in our digestive system, so stimulating this nerve could improve digestion and help treat conditions like irritable bowel syndrome (IBS). Surgical VNS is even used in some cases of gastroparesis, a state where the stomach takes too long to empty its contents.
On this topic, we should also touch on the gut-brain axis, a system of communication between the brain and gut via hormones, chemicals, and the vagus nerve. This axis is essential for our overall health since it helps regulate energy balance and nutrient absorption in the body. Therefore, stimulating the vagus nerve could help maintain healthy communication between these two systems, promoting better emotional and digestive health.
Could regulate moods
Studies have shown that vagal stimulation may benefit people with depression or anxiety. It's thought to increase serotonin and dopamine levels in the brain, thus helping to reduce feelings of stress and anxiety.
Even for those who don't have diagnosed mental health issues, stimulating the vagus nerve may help reduce everyday stress and improve overall mood.
Could improve heart health
The vagus nerve is essential for controlling heart rate and blood pressure, so stimulating it could benefit those with cardiovascular issues. In addition, research suggests that VNS has a positive effect on arrhythmia (irregular heartbeat) as well as hypertension (high blood pressure).
Could help you recover faster
Another benefit many VNS users report is faster recovery times. Since VNS helps reduce inflammation and regulate the body's stress response, it can help speed up healing after an injury or illness. Some athletes also use it to help them recover from intense workouts.
Could promote tranquility
Interestingly, many people who try vagus nerve stimulation also report feeling more tranquil as they go about their daily lives.
Could enhance cognition
Cognitive skills, including memory and recall, could also benefit from vagus nerve stimulation. In addition, research suggests VNS can help improve cognitive performance, even in people with Alzheimer's or dementia.
Methods of Vagus Nerve Stimulation
Next, let's explore the various methods of vagus nerve stimulation.
Surgical VNS
There are a few conditions that have FDA approval for surgical VNS. This means that if a doctor believes VNS to be the best treatment option for a patient, they may implant a vagus nerve stimulator (VNS device) into the body. Some of these conditions include treatment-resistant depression and epilepsy.
For surgical VNS, the procedure is similar to that of having a pacemaker installed. It involves placing a vagus nerve-stimulating device under the skin in the chest. The device targets the vagus nerve and emits electrical pulses at regular intervals.
Non-invasive VNS
The good news is surgery isn't required if you're eager to experience the wellness-enhancing benefits of VNS for yourself.
Transcutaneous vagus nerve stimulation (tVNS)
In this case, the vagus nerve is stimulated through the skin rather than needing to be done under it, as is the case with surgical VNS. For example, Xen by Neuvana entails using special headphones that stimulate the vagus nerve through the ear.
If you recall, we said the vagus nerve combines with the accessory nerve in the neck. This makes it easy to stimulate the vagus nerve through the ear since there are a number of nerve endings close by. This is why tVNS is often done on or near the neck and the ears.
Today, tVNS is a lot more accessible than it used to be, and various products on the market make it easy to stimulate your own vagus nerve. Again, this includes Xen by Neuvana.
Users can wear their headphones and control their VNS session with a handheld device and a smartphone app. This gives them the power to customize their VNS treatment and experience greater comfort and relaxation. They could be sitting on their couch, on their porch, lying in bed, or going about their day while their vagus nerve stimulation device works its magic. (And by magic, we actually mean science!)
Cold exposure
Another non-invasive option for stimulating the vagus nerve and reaping the power of the parasympathetic nervous system involves intentional cold exposure. For that reason, cold plunges have become increasingly popular among the health-conscious crowd.
When you submerge your body in a cold body of water, you're activating the vagus nerve at the same time. Furthermore, many experts suggest that regular cold exposure helps reduce inflammation and reverse oxidative damage, which is essential for healthy aging.
There's no need to jump into the ocean to experience this effect for yourself, either. Instead, you might try a cold shower, splashing your neck and chest with cold water, or holding an ice pack on your neck/chest to achieve the same benefits.
Yoga
One of the reasons you might enjoy your yoga practice so much could be that you're successfully stimulating your vagus nerve. In addition, as most practitioners will report, yoga can effectively reduce stress and anxiety levels.
This could be due to the combination of deep breathing, stretching, and meditation incorporated into many yoga practices today - all of which have been known to stimulate the parasympathetic nervous system and calm the mind.
Acupuncture
Acupuncture is believed to stimulate the vagus nerve as well. This ancient practice involves inserting thin needles into specific points on the body to promote overall wellness. And as it turns out, acupressure points for releasing stress are often located around areas with nerves that connect to the vagus nerve! This means acupuncture might bring relief from pain or tension and offer some of the same benefits as VNS, such as reducing stress levels.
Gargling, singing, and humming
Again, this VNS method brings us back to the vagus nerve's position in our body and how it intertwines and connects with the accessory nerve. Since our voice box (larynx) gets its motor function from the accessory nerve, it makes sense that certain sounds and vibrations could stimulate the vagus nerve.
So next time you feel stressed and overwhelmed, try gargling or humming your favorite song! It might sound funny, but who knows - maybe it will have some real physical benefits too.
Parasympathetic Nervous System and the Vagus Nerve: FAQs
Considering this complex topic, it's natural to have a few lingering questions about how the parasympathetic nervous system and the vagus nerve work together.
Here are some of the most common questions we hear about this topic.
How does VNS work to activate the parasympathetic nervous system?
The vagus nerve is the main communication line between our brain and the organs in our body. By stimulating this nerve with VNS, neurons are activated and send a signal to the brain, activating the parasympathetic nervous system. Then, when the parasympathetic nervous system kicks in, our rest and digest response can too! This can mean more calm, better sleep, balanced hormones, improved digestion, and a more relaxed state overall.
Is VNS safe for everyone to use? Are there any contraindications?
Non-invasive VNS is considered a safe and effective treatment for virtually everyone. But, of course, it's always a good idea to consult with your physician before starting any therapy, even if it is non-invasive.
As for contraindications, people with certain medical devices, such as a pacemaker, should not use VNS. Additionally, pregnant women and people with a history of seizures, irregular heartbeat, or other similar conditions should speak with their doctor before using this treatment.
Are there any side effects associated with VNS?
Surgical VNS for serious medical conditions is more likely to have side effects than non-invasive methods of vagus nerve stimulation. For example, patients may experience hoarseness in their voices, changes in appetite, and abdominal pain.
The side effects of using VNS for health and well-being (such as reducing stress or improving sleep) are usually minimal and short-term. Some people may feel dizzy, nauseous, fatigued, or have a mild headache during their session. This often goes away after a few minutes of rest.
How long does a typical VNS treatment last, and how often is it typically recommended?
This largely depends on the type of vagus nerve stimulation treatment you undergo. For example, most medical trials involve at least four weeks of ongoing VNS. For things like tVNS, cold exposure, and other non-invasive options, the duration and frequency of each session varies.
But keep in mind, the more glimpses of relaxation you offer your brain with VNS, the more it will become accustomed to and benefit from the sensation. So it's best to be consistent and schedule VNS sessions as often as possible for optimal results.
Can I stimulate the vagus nerve at home?
Absolutely! In fact, there are more effective options for doing so than ever before. For example, you can try cold exposure, singing or humming, and even tVNS (transcutaneous vagus nerve stimulation).
When done correctly and consistently, each of these methods can help balance your nervous system and provide deep relaxation - all from the comfort of your own home.
Last Words
We've covered a lot today about the parasympathetic nervous system and the vagus nerve, so let's recap. The parasympathetic nervous system is responsible for our 'rest and digest' responses, which help us to relax and restore balance throughout our body. Vagus nerve stimulation (VNS) can activate this response and provide a plethora of health benefits like a brighter mood, improved digestion, a relaxed state overall, etc.
VNS can come in many forms - from medical treatments such as surgical VNS to more natural methods like humming or singing. And if you're looking to do it at home, you can also try tVNS with Xen by Neuvana for an effective option you can use at home.
No matter which method you choose, the power of the parasympathetic nervous system and its associated relaxation responses can be accessed through vagus nerve stimulation.
