Your second, almost unknown brain

What is the enteric nervous system?

The enteric nervous system (ENS), as a part of the autonomic nervous system, is simpler in structure than the brain but nonetheless highly complex. The ENS consists of up to 600 million nerve cells embedded in our digestive tract. If our brain had to take over the ENS functions, the connecting nerves would be too bulky. It's therefore a good thing our gut can take care of itself.

How do gut and brain communicate via the gut-brain axis?

The connection between gut and brain is called the gut-brain axis. This axis has a 'highway' – the vagus nerve, which links the two organs neuronally and helps them communicate through various chemical messengers. 

The gut microbiota is also involved in this communication. What the gut 'tells' our head is mostly unnoticed, yet the ENS regulates, without our conscious participation, the hormones that tell the brain when and how much we should eat. It also signals the brain when we are full and triggers nausea if we have eaten too much. 

What role does the microbiota play for our wellbeing and under stress?

Almost everyone has felt it: stress causes gut problems and gut issues cause stress in return. What not everyone knows is that, to some extent, whether we cope well with stress or are easily overwhelmed depends on the state of our microbiota. It is an important player in the interplay between gut and brain. 

Under stress, different bacteria survive than in relaxed times. There are bacteria that increase our appetite under stress and others that induce premature satiety. 

The feel-good hormones serotonin and dopamine are produced more than 90% in our belly, where they control gut activity. These pleasure hormones can affect our brain's emotion centre (the limbic system) via the vagus nerve and thus influence our mood. No wonder that the way we deal with stress seems to be, to some degree, 'laid in the gut'. A stressed gut affects the psyche.

How does the enteric nervous system influence our emotions and gut feeling?

It is also known that joy, uncertainty, grumpy moods and wellbeing do not come solely from the brain in our skull. 

In her book “Darm mit Charme” Giulia Enders writes: “Our gut feeling plays a big part in how we feel. We are 'scared' or 'petrified' when we are anxious. 'We can't get anything done' when something doesn't work out. We 'swallow disappointment', need to 'digest' defeats first, and a nasty remark 'leaves a bad taste'. When we are in love, we have 'butterflies in the stomach'. Our 'self' consists of head and gut.” 

Messages from the gut reach the head via the vagus nerve, which runs up from the abdomen along the oesophagus, through the diaphragm between lung and heart, up through the neck into the brain. Thus, for example, our gut can alert the 'vomiting centre' to an unusually high alcohol content or inform the 'pain centre' about severe bloating.

What protective functions does the enteric nervous system perform in the body?

The enteric nervous system also has a protective function. The food we eat can contain potentially dangerous bacteria. Between 70 and 80 percent of lymphocytes — an important part of immune defence — are located in the abdominal cavity. If too many harmful organisms enter the body, the ENS triggers strong contractions and expels toxins from the body through vomiting or diarrhoea.

Optimising the gut-brain axis: small changes, big impact

• Pay attention to a healthy, balanced diet to create a supportive environment for beneficial gut bacteria.
• In times of stress, breathing exercises or deep breaths help relaxation. They stimulate the vagus nerve, lower blood pressure and heart rate, boost digestion, reduce muscle tension and stimulate the immune system.
• An effective breathing exercise is the so-called box breathing: inhale (4 seconds), hold (4 seconds), exhale (4 seconds) and hold (4 seconds). It helps to cope with stressful situations.
• You can do a self-massage. Place both palms on the outer sides of the neck and stroke the skin with gentle circular movements between ear and shoulder. Since the vagus nerve runs along the sides of the neck, this stimulates it and promotes calm and relaxation.
• A good exercise that positively influences the vagus nerve is turning the head. Slowly turn your head to the left and fixate something near you with your eyes. Then slowly turn to the right and briefly focus on an object there as well. Repeat a few times. This stimulates the part of the vagus nerve that runs through the neck and the eye muscles, which are also connected to the vagus nerve.
• A fun exercise for those who can wiggle their ears: raise your eyebrows while moving your ears. This activates the temporal muscle and the seventh cranial nerve, which has an effect on the vagus nerve.
• Gargling can activate the vagus nerve. Simply take a glass of water and gargle. The throat and larynx muscles are closely connected to the vagus nerve.
• Activate the parts of the vagus nerve that run along both sides of the neck by vibrating your voice. Sing your favourite songs. Songs rich in vowels like A, O and U are best suited. Not enjoying it? Simply chant "Ooommmm" like meditating monks.
• Calm down the excitatory part of the nervous system and activate the vagus nerve with cold stimuli. Let cold water run slowly over your arms and legs first and then down the neck across the whole body.
• Stimulate your vagus nerve with accommodation exercises. Extend one finger of your right hand and one finger of your left hand at different distances from you and try to focus alternately on them with your eyes. The eye muscles are connected to the vagus nerve and such eye muscle training leads to pleasant relaxation.

Our second brain cannot think or decide for us, but it strongly influences our quality of life. With these simple tricks you can stimulate it and enhance your wellbeing!