From "Brain Gut Microbiome Interactions and Functional Bowel Disorders":

In response to external and bodily demands, the brain modulates individual cells (ECC – enterochromaffin cells; SMC – smooth muscle cells; ICC – interstitial cells of Cajal) within this network via the branches of the autonomic nervous system (ANS) (sympathetic and parasympathetic/vagal efferents) and the hypothalamic pituitary adrenal (HPA) axis.

What is the meaning of "external demands"? What other possible demands can the brain strive to meet by modulating the activity of the neural network of the gut?


1 Answer 1


From the context, it seems to refer to those demands outside of the human body. i.e. perceptions of the external world. Examples could include a perceived threat, diunal cycles, or stress about that public presentation you're giving later.

If you are about to be chased by a dangerous predator, a sudden urge to poop would probably impair your chances of survival. Luckily, when our sympathetic nervous system kicks in, our GI motility slows down, so our body can focus on surviving the external threat and live to poop another day.


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