Is it true that we have a second brain in the stomach?

Is it true that we have a second brain in the stomach, due to its nervous activity?

Society is advancing technologically by leaps and bounds, and with it, the knowledge and understanding of ourselves and the world around us.

Modern medicine and genetic studies are disciplines that continually challenge preconceived ideas, and thanks to new research, organs of our own body that we thought we already knew are rediscovered with new and fascinating properties.

Such paths lead us to such outlandish statements as "we have a second brain in our stomach". An alien concept for everyone, since we only know of one neuralgic center in our body and this is located inside the cranial cavity.

As with everything in the world of science and biology, we cannot state outright that this postulation is entirely true. Do we have a second brain in our stomach? Yes and no. Read on to discover the correct answer to this question.

A second brain in the stomach: between the myth and the truth

It is clear that in order to understand the concepts to be covered in this opportunity, it is necessary that we first establish the general functioning and structures of both organs involved.

1. About the brain

The brain is the nerve center of the nervous activity of all higher animals, including the human being. It is responsible for thought, memory, speech, language, reflexes and bodily motor control.

A typical brain slice shows two distinct types of tissues: the white matter and the gray matter.. The former presents this "faded" color thanks to the axons of the neurons, those terminations in the form of a "necklace of beads" responsible for transmitting the nerve impulse.

On the other hand, the gray substance corresponds to the agglutination of the neuronal bodies, i.e. the somas.

In order not to get lost in the physiology of the lobes that make it up, we will limit ourselves to say that the brain weighs about one and a half kilograms and that its cortex contains more or less two or three kilograms. and its cortex contains more or less two trillion neurons.. These figures speak for themselves about the extreme importance of this organ in the physiological framework of the human being.

2. About the stomach

The stomach, in turn, corresponds to the dilated section of the digestive tract between the esophagus and the intestine.. Together with the duodenum it forms part of the proximal infradiaphragmatic portion of this system.

We could get lost in the physiology of this structural complex, but again, with a few facts it is more than clear the importance of the stomach for human functioning. This portion of the digestive tract is approximately 25 centimeters high and has a capacity of more than one liter in volume.

It presents a complex mucosa organized in a series of gastric folds, which are highly irrigated and innervated. After all, the function of this section is food decomposition.Therefore, ample contact with the rest of the body is essential.

As we have seen in these lines, the brain and the stomach have little to do from a purely physiological point of view. Yes, both are an integral part of human functioning, but what makes some people claim that we have a second brain in our stomach?

A question of neurons

The answer lies in the neuronal composition of both structures.. We have already said that there are about two trillion neurons in the cerebral cortex, a figure that is certainly not possible to compete with. Yet, in the stomach environment we can find more or less 100 million neurons, i.e. more than those present in the spinal column (or the same as those found in the brain of a cat).

It is because of this neuronal grouping that some media claim that the stomach is our second brain. But what is the function of this neuronal clustering in the stomach? We will reveal it to you below.

1. Regulation of energy balance

The maintenance of weight and body composition depends on hypothalamic factors (i.e., secreted by the hypothalamus) and non-hypothalamic factors, such as those produced in the intestinal tract. which concerns us here.

The stomach alerts the central nervous system (CNS) of the individual's nutritional status and energy homeostasis through distention signals and metabolic processes, i.e. presoreceptors and chemoreceptors. Various protein complexes such as insulin and leptin are generated in a modulated manner in the Gastrointestinal tract depending on the individual's state, which react with central neuropeptides to modulate appetite..

To summarize a little the agglutination of terms shown previously, it could be said that the central nervous system and the stomach participate jointly in the modulation of appetite and energy expenditure in the short and medium term. Investigating these correlations is not trivial, since obesity is an increasingly worrying pathology at the health level (it is present in 10% of the European population) and understanding the mechanisms of its emergence is one of the first steps to curb it.

Modulation of the emotional state

It is not all a matter of neurons, as preliminary studies seem to indicate that there is a clear correlation between the emotional state of the individual and his or her emotional state. correlation between the emotional state of the individual and his or her intestinal microbiota..

We define the microbiota as the set of microorganisms (bacteria) associated in colonies that have evolved together with the human being in a state of symbiosis. a state of symbiosis. These, in the digestive tract, are responsible for promoting the synthesis of vitamins, digesting compounds of vegetable origin and promoting the specialization of the immune system, among others.

What was not so clear until relatively recently is that the composition of the gut microbiota appears to modulate brain development and function and even the individual's moods. For example, preliminary research has shown that there is a clear difference in the microbiota between patients with depression and people who do not suffer from this disorder.

In addition, an increasing number of studies point to possible correlations between autism spectrum disorders (ASD) and dysbiosis (microbiota imbalance) in the gastrointestinal tract.. Of course, there is still a long way to go to fully understand these interactions.

Moreover, 90% of the concentration of serotonin, a molecule that directly modulates human emotions, is found in the gastrointestinal tract. Neurons in the myenteric plexus synthesize it to control intestinal secretions, motility and sensations.

3. Manifestation of stress

As we have seen, the stomach is an important factory of neurotransmitters, the engines of our mood. This portion of the digestive tract warns us, in different ways, that a situation of stress continued over time is not at all sustainable.

Hormones such as cortisol (produced in the adrenal gland) promote gastric acid secretion, among other things. Prolonged exposure to stressful and anxious situations therefore causes dysbiosis (imbalance in the gut microbiota) in the sufferer. This leads to intestinal dysfunctions and reduced regeneration of the digestive mucosa, among other things.

All these mechanisms of action and many more can generate in the patient cramps, pain, gas, reflux and even promote the appearance of ulcers. Thus, the stomach warns us that we have to reduce the stresses of the routine if they get out of control.

Conclusions

As is obvious from the outset, we can affirm that we do not have a second brain in the stomach. This denomination is the result of an enormous exercise of abstraction, because the neuronal agglutination in the stomach system functions in a very different way from that present in the encephalic mass..

Even so, as we have seen, the stomach does modulate, to a certain extent, moods, responses to stress and, of course, the appetite and energy balance of the individual.

Finally, we do not want to end this opportunity without making an appeal to the search for real knowledge and the filtration of information. When talking about this type of topics, we cannot make categorical statements, and it is necessary to be suspicious of those who do so. No, "An imbalance of the microbiota does not cause autism", rather, "the microbiota among people within the autism spectrum seems to be different from that of people without this disorder, so both could be correlated".

It is necessary to filter the information with caution and reserve, because in the world of physiological interactions within the human body there is still much to be known and investigated.

Bibliographic references:

• Dinan, T. G., & Cryan, J. F. (2017). Brain-gut-microbiota axis-mood, metabolism and behaviour. Nature Reviews Gastroenterology & Hepatology, 14(2), 69-70.
• Kolb, B., & Whishaw, I. Q. (2006). Human neuropsychology. Ed. Médica Panamericana.
• Martinez, J. A., & Solomon, A. (2006). Involvement of the nervous system and gastrointestinal tract in energy homeostasis. University of Navarra Journal of Medicine, 27-37.
• Navarro, A. N. D. R. R. E. A. (2009). Surgical anatomy of the stomach and duodenum. Digestive Surgery, 1-22.
• Ostrosky, F., & Neuropsychology, D. L. (2010). Brain development. Neurosciences, National Autonomous University, 1-10.
• Zacarias, M., Cadena, M., & Rivas, P. (2009). Structural modifications in the stomach and liver of Paralabrax maculatofasciatus (Steindacher, 1868) under chronic stress. International Journal of Morphology, 27(2), 425-433.