The human body does a pretty good job at keeping critical systems functioning without interrupting our binge watching or bowling night—the gut digests lunch on its own, the heart keeps pumping and our bodies regulate temperature. That’s all due to the autonomic nervous system. In the presence of stress, like the sudden appearance of Freddy Krueger, a section of the ANS called the sympathetic nervous system kicks in, which turns on our fight or flight response.
Until recently, researchers believed the sympathetic nervous system was wired with one type of nerve tissue and had a simple on/off switch that caused goosebumps, increased the heart rate, and turned on the sweat glands no matter the stimuli. Researchers now know that the sympathetic nervous system is much more complicated and activates different organs depending on whether you’re watching a horror movie or jumping into a cold pool. A new study, published in the journal Nature Neuroscience, investigated the system further and found that it has at least eight different types of neurons associated with it, each of which controls a different reaction, reports Ian Sample at The Guardian.
“We’ve shown that the sympathetic system consists of many types of neuron that regulate specific functions in the body,” lead author Alessandro Furlan, a researcher at the Karolinska Institutet in Sweden, says in a press release. “For example, one thing we found was that goose bumps and nipple erection are caused by neurons that are specialized to regulate these functions by controlling the erectile muscles in these tissues.”
The team found the nipple nerves by studying cells in the spines of mice. The researchers stimulated various parts of the body and then traced the nerves associated with the sympathetic nervous system to these stimulated parts, Sample reports. They then looked at the nerve cells, classifying them based on their genetic activity. Through this analysis, they were able to tease out the eight different nerve types. These paths control a variety of reactions, including goosebumps, nipple erections, sweating and blood flow. Yet researchers are still not sure what three of these nerve types control.
“We knew there must be multiple types of nerves wired to different tissues and organs, but we didn’t know what they were,” Sten Linnarsson, a co-author of the paper tells Sample. “It’s the same challenge that an electrician faces when they wire up a house. If the wires all look the same, it’s going to be hard to wire them up correctly.”
Now, the researchers say in the press release they will look at how this complex system forms during gestation and how each of these eight nerves controls various sympathetic functions.