Here at Seeker World Headquarters -- actually a parallel dimension anchored in rural Indiana -- we like to keep up with our favorite periodicals: Geophysical Research Letters, Advances in Physics, the Journal Of Investigative Dermatology....
And so a recent study published in Nature Neuroscience caught our eye, as it promises to solve an abiding mystery: Why do our nipples get hard sometimes? Julian Huguet gets to the point in today's DNews report.
Researchers were studying the sympathetic nervous system, which is mostly known for triggering the fight-or-flight response, but is actually behind several biological mysteries, including pruney fingers. While experimenting with mice, the scientists followed nerves from the spinal cord to where they connect to other structures like the blood vessels, muscles, and yes, nipples.
RELATED: Does Acupuncture Even Work?
It turns out that there are distinct types of neurons wired to specific areas, each expressing different genes and programmed to respond to different stimuli. All indications are that there is, indeed, a nipple neuron. It's triggered by the neurotransmitter norepinephrine and causes your areola to contract. (A similar neuron causes goose bumps.)
The new study provides an answer to nipple question on the technical level, but what about the big picture? We know that hard nipples are good for breastfeeding -- that's a whole 'nother thing. But why do our nipples tend to get hard in other circumstances -- when it's cold, or when we're sexually aroused, or when the Sunday New York Times crossword puzzle comes out? (That may be a more personal thing.)
The science is a little fuzzier on this end. It's possible that hard nipples are supposed to serve as a signal of arousal, but it's a pretty lousy signal if it also happens just because it's cold. It's possible that the nipple response might be a vestigial trait from when we were more hirsute. The phenomenon appears to be related to triggers that cause our hair to stand on end.
Jules has more details in his report, or click on over to our coverage of the obvious next question: Why Do Men Have Nipples?
-- Glenn McDonald
Live Science: What Nerve: Different Nerve Cells Cause Hard Nipples, Goose Bumps
ScienceDaily: Sympathetic Nervous System
Refinery29: Scientists Finally Figured Out How Your Nipples Get Hard