By: Dr. Lalit Mehra
The term autonomic nervous system conjures up in our minds, an image of a set of nerves supplying the smooth muscles of GIT stimulating peristalsis, and supplying the cardiac muscles either increasing or decreasing the rate and force of contraction. The idea of preganglionic and the postganglionic neuron and the chain of sympathetic ganglia abutting the vertebral column is all too familiar to a medical student, since the very beginning of medical school. The effects of sympathetic nervous system are widespread including on the skin covering every inch of the human body and all the appendages associated with it like sweat glands. On the other hand, the action of the parasympathetic system is more focused on internal viscera. From changing the diameter of the pupil to focus on a near object, to relieving a full bladder (or holding it), there are few internal functions of the human body which are not influenced by the autonomic nervous system.
A man bungee jumping from the Rio Grande Bridge to make his vacation memorable is making good use of his body’s sympathetic system. While a woman who instead prefers to bask in the sun on a white-sand beach enjoying a Mojito has given the role of her body’s homeostasis to the parasympathetic system.
We are all too familiar with the effects of the two parts of ANS working together to balance the body in a tug of war between stress and relaxation. However an area of ANS which still remains enigmatic even after years of research is its afferent limb. This part is often ignored in textbooks except for the references generally with respect to referred pain. Our minds refer the pain of myocardial infarction MI to the left arm (in a way erroneously) as it probably did not receive the proper training to recognize visceral pain as well as somatic pain. After all it is not every day that we have an MI.
Other than these pain sensations our Autonomic nervous system carries millions of afferent sensations to the CNS every second which probably never get registered in our conscious minds. We all remember feeling dull after eating too much at a lunch buffet. Can we describe the feeling? Well not really, just like we can’t describe our feelings after listening to a beautiful piece of music. We “know” and yet we don’t.
Let us just call these feelings: “Gut Feelings”.
Do our guts have feelings? Yes they do. Not probably the kind of feelings you could make a romantic comedy on, but yet quite palpable only if at a subconscious level. Recent research suggests that microorganisms in the GIT may influence what we eat by altering these afferent impulses. So next time you have a craving for the chocolate, remember it might be a bacteria in your colon actually sending in an order to your mind to supply it with the sweet stuff. And next time you are feeling low; don’t rush to the psychiatrist immediately. It might just be a tub of ice-cream tumbling through your intestinal loops and your gut telling you to go easy on it the next time.