Caltech Scientists Make Breakthrough in Understanding How Our Bodies Handle Stress and Digestion

In a discovery that could change how doctors treat digestive disorders, Caltech scientists have uncovered new details about how our nervous system controls our gut and other internal organs.

The research team has shown that the body’s stress response system is far more sophisticated than previously thought. Rather than being a simple “all or nothing” response, it can fine-tune individual organs with surprising precision.

“The anatomy and function of the autonomic system has been known for over a century, but we have surprisingly little understanding of cellular and functional diversity of autonomic neurons,” explains Caltech Biology Professor Yuki Oka.

Most people are familiar with the “fight-or-flight” response — that surge of energy we feel when startled or scared. This response comes from what scientists call the sympathetic nervous system, which works alongside the parasympathetic system, described as the body’s accelerator and brake, respectively.

Using cutting-edge techniques, Wang and colleagues discovered specialized neuron populations.

“Discovering the diverse sympathetic neuron populations with organ-specific innervation was electrifying, because it allows for precise control and modulation of body functions,” says Tongtong Wang, the Caltech graduate student who led the study, published November 27 in Nature.

The team found specialized groups of nerve cells, each controlling different digestive functions. One group regulates the release of bile (a fluid needed for digesting fats) and hormones that control blood sugar, while another group controls the movement of food through the intestines.

“It was like flipping switches in a complex machine and watching how each part responds,” Wang explains.

This finding challenges the traditional view that stress affects all organs in the same way.

“The modular arrangement we uncovered means that the body can fine-tune each organ’s activity without affecting others,” explains Oka. “It’s a level of control that we did not fully appreciate before.”

To measure these subtle changes, the team collaborated with Wei Gao, a Caltech Professor of Medical Engineering, to develop an ultra-sensitive device that can detect microscopic changes in bile secretion.

The implications could be significant. Many common health conditions, from digestive issues to stress-related disorders, might be better understood and treated based on this research. The study also shows that the stress response isn’t just about dealing with immediate dangers — it helps regulate basic body functions like blood sugar levels.

The research team included Caltech postdoctoral scholar Bochuan Teng and graduate student Dickson (Richard) Yao, along with Gao.

The complete study, titled “Organ-specific Sympathetic Innervation Defines Visceral Functions,” builds on earlier research by the Oka laboratory, which in 2022 discovered how the body signals the brain about hydration levels.