Imagine yourself late at night. You're walking alone towards your car through a dark, desolate parking garage. Its deathly quiet, but you hear something. Footsteps. Footsteps behind you. They start to quicken. They are getting closer to you. Closer and closer...

As you reflect on going through this kind of experience, you would certainly expect to be affected emotionally, but what would you expect physically? What happens to your body? What kinds of physiological reactions take place?