Gutsy: Hey Mindy! What’s up? I see that you are not keeping well these days. It’s really difficult for me to move things fast when you are ill!
Mindy: I’ve kind of started feeling anxious quite often.
Gutsy: Oh, that’s bad! Is there anything I can do to help you with your anxiety?
Mindy: Umm. I might need my medicines. I am running out of stock!
Gutsy: Well, send me the list, and I’ll deliver them to you.
Mindy: 4 tablets of Serotonin, 2 tablets each of Dopamine and Oxytocin, and maybe a tablet of Endorphin!
Gutsy: Ah! All the happy hormones! I got it, friend. Your order will be delivered.
Mindy: Thank you Gutsy! You’ve always been my savior.
Gutsy: No worries, my friend. Which delivery system would you like to opt for? The courier or the fax?
Mindy: Any one will do, as long as they are here!
Gutsy: You are all set, buddy. Your order will be delivered soon! I hope you feel better and then we can get back to work smoothly once again.
Mindy: Great! Waiting for it.
Gutsy: Take care till then. Bye!
Wondering who this hormone dealer Gutsy is? Well, it is none other than our Gut! And Mindy, who is desperately in need of happy hormones, is our Brain.
Our brain cells (neurons) constantly require different types of hormones to communicate with one another, which is an important process of brain and body functioning. More than 30 such hormones, known as neurotransmitters are closely associated with our gut- the microbiota residing in our gut are able to regulate the production of neurotransmitters. These neurotransmitters are capable of directly or indirectly modulating the brain function.
Isn’t it interesting how the remotely residing gut microbiota influences brain functions? This can only happen when there is a concrete connection between the brain and the gut. In our previous article, we briefly touched upon this connection; in this article, we shall explore the connection more.
We know that our gut/intestine is home to many different types of bacteria. These bacteria while thriving in our gut, utilise the nutrients that we consume and produce metabolic waste products/metabolites. Even though these metabolites are waste for the bacteria, they are useful to humans!
Eeuu! So, are we saying that bacterial poop is useful to humans? Oh yes! Certain bacterial metabolites stimulate a special type of cells in the gut which leads to an increased production of selective neurotransmitters, including the happy hormones that Mindy requires.
Hmm.. so now Gutsy must send across these neurotransmitters or at least the information encoded in these neurotransmitters to Mindy to reduce the anxiety. But, how will she do that?
Well, she can use two different types of delivery systems- the fax delivery system or the courier delivery system.
We have learnt about the Vagus nerve in our previous blog, which is the longest nerve that connects the brain and the gut. The ends of the Vagus nerves that are spread onto the gut wall have receptors that can sense specific neurotransmitters. These terminal receptors bind to the neurotransmitters present in the gut lumen, and a signal transduction through the vagus nerve is initiated. Depending on the neurotransmitter produced in the body, different signals can be sent to the Brain through the Vagus nerve.
This works just like the fax delivery system- where the original document is just scanned through the fax machine and the information is decoded at the other end and an exactly similar copy gets printed. When signal transduction takes place through neural pathway, the neurotransmitters from the gut lumen do not reach the brain physically, but simply transmit the relevant information (nerve impulse) to the brain.
Ta-da! Aren’t you impressed by how wisely our body has been constructed? Efficiency increases with the complexity it seems.
How does the courier delivery service work then?
This is the most popular system of our body, functioning continuously that connects each and every body part to one another a.k.a. the circulatory system. It not only provides a constant supply of oxygen-rich blood to all body organs, but also provide nutrients and hormones and is responsible for removing waste products from the different parts of our body.
Now, can you guess how Gutsy uses this system to deliver the neurotransmitters to Mindy? The capillary network in the gut wall absorbs the neurotransmitters and they travel all the way through our blood to the brain, much like a parcel (courier) is physically delivered to the designated address. And just like a courier must be signed off by the recipient upon delivery, the delivered neurotransmitters too must be approved by a special type of cells of the Blood Brain Barrier (BBB) – which is the shield or a gate, around our brain. It is only upon approval that the neurotransmitters are able to cross the blood brain barrier and modulate the brain activity.
We now know that the Neural Pathway (fax delivery system) and Circulatory Pathway (courier delivery system) are the two main routes through which the Gut-Brain connection manifests. But which system is more efficient for the different types of neurotransmitters? And does Gutsy always use the same system for delivering the hormones to Mindy? We shall reflect upon these questions and also talk about the specific influence that neurotransmitters have on our brain activity, in the upcoming articles.
In the meanwhile, rest assured- Mindy might have surely received her order of happy hormones by now! Hurray!
Disclaimer: The content of this article is meant for educational and creative purposes only, and will not be directly used for generation of profits. All rights and responsibilities, including the authenticity of the information presented in this article belong to the original authors and their publications (listed below in the Bibliography section), and there is no copyright infringement intended.
Bibliography
- Bacterial Metabolites of Human Gut Microbiota Correlating with Depression
- Effects of the enteric bacterial metabolic products
- Indigenous Bacteria from the Gut Microbiota Regulate Host Serotonin Biosynthesis
- Vagus Nerve as Modulator of the Brain–Gut Axis in Psychiatric and Inflammatory Disorders
- The Impact of Gut Microbiota Disorders on the Blood–Brain Barrier
- Gut microbes and metabolites as modulators of blood-brain barrier integrity and brain health
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