We all know that we have a brain in our heads – but did you know that we have a second brain? And that it’s located in our gut? It’s official name is the Enteric Nervous System (ENS) – but I think Eric is easier to remember, don’t you?
Eric the ENS has at least 100 million neurons, which is about the same as a cat’s brain – and you know how smart cats can be! This brain is not a mass, as the brain in our head: rather it is a sort of mesh, or network, located under the mucosal lining and between the muscular layers of the esophagus, the stomach and the small and large intestines, so it is several metres long.
Eric the ENS is connected to the brain in our head by the Vagus Nerve, that runs from the abdomen to the brain. But if the Vagus Nerve is cut, Eric the ENS continues to function quite happily, controlling and co-ordinating the process of digestion and all that goes with it. In fact, some 90% of all the signals that pass along that Vagus Nerve are messages from Eric to the brain, and not from the brain to Eric – so it could be said that, actually, Eric’s in charge!
Just think for a moment of all the common expressions we use – “I’m gutted”; “it’s a gut reaction” “I can’t stomach it any more”; “I’ve got butterflies in my stomach” – to mention a few. These are all linked to responses from Eric the ENS to our moods and emotions: in fact it is often Eric the ENS who tells the head brain how we are feeling!
What does Eric the ENS do? Quite a lot, actually –
- it controls the mechanical blending of food in the stomach, and ensures that the pH balance is right at various sections of the system. When we digest food it goes through a process where it is first broken down by an alkaline mix and then by a special acid mix: it is important to keep the two separate and both working as they should.
- it identifies bad bacteria that may have got into the system via the digestive system (eg in something you have eaten). If the sensors on the gut wall detect something that shouldn’t be there, substances such as histamine are released. This alerts Eric to one of several responses – diarrhea perhaps, or a message up the Vagus Nerve to the head brain, who will trigger vomiting: both designed to get the bad stuff out of the system.
- it produces as much dopamine (the pleasure and reward molecule) as the head brain.
- it produces lots of serotonin too. Serotonin is the “feel good” molecule that helps counter depression and regulates sleep. Serotonin that is produced in the ENS passes into the blood stream and helps to repair damaged cells and supports processes such as bone density.
Considerable research is being done on the links between Eric the ENS and not only moods and emotions but also physical conditions. For instance, stress triggers the gut to produce more ghrelin, a hormone that reduces anxiety levels – but it also stimulates feelings of hunger. Hence comfort eating at times of worry and stress – blame it on Ghrelin the Gremlin! And when we have had enough, then PYY comes to the rescue – that’s the chemical that sends the message to the head brain that says, “I’m full.” But that takes the slow route – it can take up to 20 minutes for the brain to get that “I’m full” message, which is why we should eat slowly. Not only does it give Eric and his team time to digest the food in a more efficient way, but it allows time for the PYY to send the full message at the appropriate time, rather than when Eric has been bombarded with a pile of food that has to be sorted through, analysed and sent to the relevant areas for processing!
So next time you have butterflies in your stomach, or you have a gut reaction to something – think of Eric!