Final answer:
Hair serves multiple functions including protection, sensory input, thermoregulation, and communication. However, regulation of body temperature is not a function of hair.
Step-by-step explanation:
Hair serves a variety of functions, including protection, sensory input, thermoregulation, and communication. For example, hair on the head protects the skull from the sun. The hair in the nose and ears, and around the eyes (eyelashes) defends the body by trapping and excluding dust particles that may contain allergens and microbes. Hair of the eyebrows prevents sweat and other particles from dripping into and bothering the eyes. However, regulation of body temperature is NOT a function of hair. Hair also has a sensory function due to sensory innervation by a hair root plexus surrounding the base of each hair follicle. Each hair root is connected to a smooth muscle called the arrector pili that contracts in response to nerve signals, making the external hair shaft 'stand up' to trap a layer of air for insulation.