When you’ve only got one job to do, you want it to be a good one, although new research has revealed that there exists a highly specialized type of nerve cell that does absolutely nothing except generate nipple erections. Reporting their discovery in the journal Nature Neuroscience, the study authors also describe another type of neuron with the sole purpose of creating goose bumps.
Both of these functions are normally involuntary, occurring when we feel cold or afraid, for example. Like many other automatic processes, they are controlled by the sympathetic nervous system, which coordinates and regulates our unconscious bodily functions.
Until now, little had been known about the types of neurons that make up this system, and it was for some time assumed that just one type of non-specific nerve cell was involved in transmitting impulses to each of the various organs affected by the sympathetic nervous system. However, this latest research reveals that the sympathetic nerve system is actually composed of several different types of neuron that regulate specific bodily functions.
To conduct their investigation, the researchers examined the genetic profile of neurons extracted from mice over the first few days of their lives, discovering that during this period, these cells become specialized for a range of specific functions.
During their experiments, the study authors found that the nipple-erector muscle tends to develop during the first three days of a mouse’s life, as does the pilo-erector muscle (which is responsible for making hairs stand on end in order to generate goose bumps).
Once these muscles have formed, some generic neurons begin to differentiate into more specialized types. For instance, around five days after mice are born, a type of nerve cell called NA2 neurons suddenly appears and becomes connected to the nipple-erector muscles, while another type, known as NA4-5 neurons, connects up to the pilo-erector muscles.
"We've shown that the sympathetic system consists of many types of neuron that regulate specific functions in the body," explained study co-author Alessandro Furlan in a statement. "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."