When someone runs their hands over your back in just the right way, or when you’re watching/listening to a sensational part of a movie/song, or when you just get really excited in general… biologically, what causes those chills to go up your spine? What’s going on here?
In addition, please excuse me for my deluge of initial posts. These are questions I have accumulated over the past year that I haven’t been able to find any decent answers to. Thanks in advance for everyone’s input. 
Music Is Food To The Brain
Brain areas activated by food or sex are also turned on by music, researchers say. Scientists used PET (positron emission tomography) to measure blood flow and thus brain activity in ten musicians as they listened to music. Music that the participants had chosen as beautiful enough to send “shivers down the spine” elicited a response in areas of the brain previously linked to sex and food. Listening to other music, general noise or silence did not have the same effect, according to a study in the Proceedings of the National Academy of Sciences. Although the participants in the study were all musicians, many people experience these chills while listening to music and may have the same brain response, says lead author Anne Blood of Massachusetts General Hospital in Charlestown, Massachusetts. Blood suggests that because music activates areas of the brain that make people happy, its soothing sounds may improve both physical and mental well-being.
http://www.calacademy.org/thisweek/archive/2001/20010926.html
So biologically, the summary of what’s going on when you get a “spinal chill sensation” is a sudden flow of blood to the brain?