Reference.com details that the function of free nerve endings is to sense temperature, pressure and pain. These nerves are known as thermoreceptors, mechanoreceptors and nociceptors respectively.
Free nerve endings relay information from the body to brain, according to Reference.com. They are unspecialized neurons, and they are the most common type found in the human body. These nerves are cutaneous, which means that they are found in the skin.
HowStuffWorks explains that thermoreceptors sense temperature. The exact nature of this process remains a mystery, but HowStuffWorks reports that some scientists suggest that the process involves the movement of ions. Mechanoreceptors deal with touch, stretch and pressure, which govern how much muscles move to accomplish a specific task, as explained by HowStuffWorks. The National Yang-Ming University states that there are more of these receptors on the fingertips and tongue than on other parts of the body. According to the university, the movement of hair stimulates these receptors because they are located close to follicles.
HowStuffWorks also explains that the third free nerve ending receptors are known as nociceptors. These deal exclusively with pain by responding to various stimuli. For example, these receptors communicate the presence of extreme heat to the brain as pain.