Eat Happy!

Eat Happy!


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Thursday, April 24, 2014

The Nervous System and Digestion

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There are many branches of the nervous system. I have talked a lot in previous posts about how the vagus nerve affects digestion and other organ actions. But, it occurred to me that I never gave a scientific explanation of where the issues originate. The nervous system is incredibly complex and very difficult to understand. I am going to do the best I can to simplify it and use terms that are easy to understand. Hopefully, the concepts of how the vagus nerve, and both sympathetic and parasympathetic system medications will be easier to understand. I am hoping it will be easier to make the science--->symptom connection clearer.

The nervous system consists of the brain, spinal cord, and sensory organs, and all the nerves that connect. Collectively, they control the body and communication. Most of us know that the brain and the spinal cord form the central nervous system (CNS). This is the headquarters of the nervous system. All of the sensory nerves and ones with organs form the peripheral nervous system (PNS).

The first branch of the PNS is the Somatic Nervous System (SNS). This includes all of the voluntary nerves. It is consciously controlled and is responsible for skeletal muscles. The second branch of the PNS is the Autonomic Nervous System (ANS). This includes all involuntary efferent (motor) neurons that carry signals from the CNS to muscles and glands. The ANS controls our subconscious muscle actions of the organs (viscera) and heart tissue. It also controls the actions of glands.

Two divisions of the Peripheral Nervous System (PNS)
There are two branches of the ANS. The Sympathetic is the classic “fight or flight.” When placed in stress or danger, the body reacts by increasing breathing and heart rate. Stress hormones are released and digestion decreases. The second branch of the ANS is the parasympathetic. This division is coined “rest and digest.” It responds when the body is relaxed, resting, or feeding. It decreases breathing and heart rate. The parasympathetic branch of the Autonomic Nervous System (a branch of the PNS) also increases digestion and helps eliminate waste from the body. This will be important information in this post. (*) This branch also helps calm the body down and undo the work done by the sympathetic branch.

Two divisions of the Autonomic Nervous System

Cranial nerves extend from the underside of the brain. There are 12 pairs. Each one has a roman numeral to identify it. Cranial nerves provide direct connection to the brain for special sensory organs such as muscles in the head, neck, and shoulders. They also innervate (supply with nerves) the heart and GI tract. The cranial nerves, GI tract, and their effect on digestion will be important information to take from this post.(**)


(**) There are a few cranial nerves that help with chewing, swallowing, and digestion. The oculomotor, trochlear, and abducens nerves (III, IV, VI) help with chewing. The glossopharyngeal nerve (IX) helps with swallowing. The hypoglossal nerve (XII) moves the tongue for swallowing. The major cranial nerve that plays a role in digestion is the vagus nerve (X). The vagus nerve travels from the base of the brain through the neck and torso. It carries information from organs to the brain. It also delivers parasympathetic signals for digestion to the organs.

Vagus Nerve Innervation

(*) As you can conclude from the photo above, the vagus nerve seems to be a catch-all. It provides the body with a sense of fullness. It functions to relax the stomach. This prepares the stomach for food. It also empties the stomach contents into the small intestines. The stomach contractions are also signaled by the vagus nerve. In conjunction with the parasympathetic branch of the autonomic nervous system, (PNS ---> ANS ---> Parasympathetic nervous system), the vagus nerve helps both contract and relax the muscles to facilitate emptying the stomach into the small intestines.


The vagus nerve runs very close to the esophagus. During fundoplication surgeries, it is possible to damage this nerve. While that sounds absolutely horrible, it isn’t an all-or-nothing deal. There are varying degrees to which it can be affected. Damage certainly does not always mean severing the nerve. To make matters worse, it is not always possible to diagnose damage. Damage cannot always be seen. There are some test that can be done. I am not familiar with these because I have not heard of them being used in children.

Close proximity of the Vagus Nerve during a Fundoplication surgery

There is a lot of research out there about the vagus nerve and it’s relation to fundoplication surgeries. Unfortunately, it is incredibly hard to sort through. I have tried to categorized this information on the Resource Pages of this BLOG. Categories include: “Surgical” and “Vagus Nerve Damage and Digestion (Gastroparesis).” I have also included a page called “Motility Contacts and Medications” to help find contacts that can help.


There are many symptoms of vagus nerve damage.

1) Gastroparesis is an extremely common symptom. This is where the stomach does not empty properly, allowing food to accumulate in the stomach. Gastroparesis must be managed with diet and medications. Over time, the body can learn to adapt to a new lifestyle that accommodates gastroparesis. Gastroparesis has no cure because of it’s autonomic-pathological causes.

2) Nausea and vomiting (potentially from the early feeling of fullness from gastroparesis) are very common vagus nerve damage side effects. 

3) Diarrhea is another common side effect. The diarrhea may improve over time.

4) Gas bloating can also occur. Excess gas in the stomach can also irritate the nerve. With gastroparesis, food remains in the stomach for too long. As food is digested, air is released. As this air remains trapped in the stomach with the food, bloating can occur. This decreased gastric emptying can be caused by the vagus nerve, but then the built up air can aggravate the nerve. It becomes a cyclical pattern that is hard to break.

5) Reflux is also a symptom. Because of the stomach's inability to hold larger amounts of food (from the backing up of gastroparesis), the stomach content may reflux back into the esophagus.

Since the vagus nerve relays messages back and forth to the stomach, as well as controlling the muscles that break down food and allow it to pass into the small intestines, it is easy to see how the slightest damage can cause large problems. There are many other symptoms that can occur. Since it is close in proximity to the esophagus, it is plain to see how easily it can be damaged during routine procedures. Gastric and esophageal (as any) surgeries create scar tissue when they heal. Scar tissue is much lighter in color, thicker, and harder to dissect. If repeat surgeries need to be done, the nerves are even harder to see. The more delicate tissues are then considerably more vulnerable to damage. The risks increases with each surgery.

An actual photograph of the proximity of the Vagus Nerve to the esophagus and stomach


Acetylcholine is a neurotransmitter (chemicals that transmit signals) that helps aid the movement of smooth muscles in the stomach, increasing gastric motility and digestion. Higher acetylcholine levels increase parasympathetic functions such as peristalsis (gastric contractions) and facilitate gastric emptying. There are both Cholinergic and Anticholinergic medications.........

1) Cholinergic medications increase the amount of acetylcholine that can attach to cells. This increases the Parasympathetic nerve function, which facilitate stomach contractions and the digestion of food. So, this means that cholinergic medications increase smooth muscle in the stomach and increase stomach motility. When erythromycin is used in low doses to increase stomach contractions, it is working through a cholinergic pathway.

2) Anticholinergic medications block acetycholine in the CNS and PNS. They inhibit Parasympathetic nerve function by blocking acetylcholine from attaching to cells. As you’ll remember from above, Parasympathetic nerves aid the involuntary movement of smooth muscles in the GI tract. Anticholinergic medications decrease the amount of acetylcholine. So, this means that anticholinergic medications decrease smooth muscle movement in the stomach and decrease stomach motility. However, these meds help ease nausea and relieve diarrhea. They are also able to ease pylorospams (exaggerated and inefficient contractions of the pylorus- the valve that empties the stomach into the small intestines).

Nausea medications and gastric motility medications work in opposite ways from one another. In most cases, one medication needs to take precedence over the other. One of Ian’s medications, Bethanechol, is an Anticholinergic. This helps ease his nausea and reduce vomiting, but as you can see...... it decreases gastric emptying. Finding a good balance between using medications is very important. We had considered using Levsin recently, which is a Cholinergic. Levsin helps relax the pylorus and facilitate gastric emptying. It would not make sense for Ian to take Bethanechol and Levsin at the same time.

It is very important to review all of your medications with your doctors to make sure you are on a correct balance. I often find that different specialists prescribe medications without realizing the others may be canceling the effects. When it comes to medications of the Autonomic Nervous system (Sympathetic and Parasympathetic), it can be extremely difficult to keep things straight.


Cholinergics: Erythromycin

Anticholinergics: Benadryl, Periactin, Bethanechol, Hydrocortisone, Neurontin

While not all of the Anticholinergic medications have strong effects, you can see how it is important to balance meds properly. Right now, Ian is on many anticholinergic medications for the treatment of mucus secretions, organ discomfort, and nausea. But, they are NOT helping him empty his stomach. This is something that needs constant evaluation.


To sum things up....

** The nervous system has two branches: CNS and PNS.

** The PNS then has two branches: Somatic and Autonomic.

** The Autonomic then has two branches: Sympathetic and Parasympathetic.

** The Parasympathetic nervous system is the one that deals the most with digestion by increasing digestion and helping eliminate waste from the body.

** A cranial nerve called the Vagus Nerve is the one with the most responsibility when it comes to organ functions. It carries Parasympathetic (digestion) signals to the organs.

** The Vagus Nerve stimulates digestion stomach contractions and stimulates the emptying of the stomach contents into the small intestines.

** The Vagus Nerve runs extremely close on either side of the esophagus and damage is listed as a risk of surgery.

** Vagus Nerve damage can create many digestive and sensory problems including: nausea, vomiting, reflux, gastroparesis, bloating, and diarrhea.

** Cholinergic medications increase parasympathetic activity and increase gastric emptying while anticholinergic medications decrease parasympathetic activity and decrease gastric emptying, but also decrease nausea.

I know I have repeated myself A LOT in this post, but I find the nervous system to be *e-x-t-r-e-m-e-l-y* confusing! I know hearing things over an over again in different words can help solidify concepts that can then be used when making good medical decisions for our children. I have been looking to put this post together for a long time because I feel it is truly important. I hope it has been a source of clarity for all of you.

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