The Enteric Nervous System, Our Gastrointestinal Overlord
My friend Suzie (musician and mad scientist) recently alerted me to the fact that our stomachs have BRAINS!
Apparently embedded in the lining of our guts is a network of up to a billion neurons (1% of the number in our head-brains) that is capable of autonomous action. It controls our digestive muscles and the secretion of enzymes, which it varies according to the bulk and nutrient composition of our food. It learns, it remembers, in a sense it can be said to understand digestion. Spooky, but its function doesn’t end there (and neither will my wild over-simplifications).
This enteric nervous system (ENS) can also release neurotransmitter goodies to reward your head-brain for providing it with food. That’s right, this thing in your belly controls you like a puppet on a string.
But you know where I’m really going here? The horrifying, primordial gravity of the situation?
Since the ability to metabolize nutrients for energy was a pre-requisite for the evolution of higher functions like locomotion, our central nervous system (head-brain et al.) developed after our enteric nervous system. This means the “second” brain in your belly was really here first.
If you turn this situation on its side and squint, you can see that our heads, our minds, our opposable thumbs…all exist in the service of our stomachs! Essentially, your entire body is one big prehensile appendage of your digestive system.
Is that why my desire for chocolate overrules my common sense?
Hah! I knew it!
No wonder it made so much sense to call my cat the Walking Stomach. I always figured it was more critical than all those other silly physiological functions.
Another interesting and spooking thing about that brain in the gut is that it also secretes and absorbs neurochemicals — the same chemicals that activate the brain systems for, for example, love. Yes, the gut is full of oxytocin receptors. And oxytocin, the “hormone of love”, also is responsible for feelings of satiety, especially after a fatty meal.
Another intriguing nugget: Kerstin Uvnas Moberg is the scientist who first identified oxytocin’s calming effects. When she blocked CCK, a substance secreted during digestion, in baby lambs, they “forgot” their bonds with their mothers.