In short, nerve cells instruct muscle cells to contract, causing our hair follicles to stand on end. Our nervous system doesn’t only direct responses to threats or changing temperatures, but also to other environmental stimuli. Scary movies or frightening stories also kickstart our autonomic nervous system and stimulate the release of epinephrine. Goosebumps are the same regardless of stimuliWhether our bodies are responding to heat changes or emotional rollercoasters, the types of goosebumps our skin produces stay the same. Our autonomic nervous system helped us survive prehistoric predators, and it will get us through the next Saw film, too.