Prime 4: Risk-taking

Human Physiology : Why Do Humans Have Adrenaline? http://www.youtube.com/watch?v=-OgVUaNZQtw&feature=related

Adrenaline: Fight or Flight Response
http://www.youtube.com/watch?v=4g25d7_Afmc&NR=1

Wingsuit Base Jumping
http://www.youtube.com/watch?v=I4U6T_BB1N8&feature=related