In the Breathe2Relax app you will find an interactive diagram of the body under the Learn section of the app.  In this section you can tap on different body parts such as the brain, ears, stomach plus more to find out the impact of the body's flight or fight response.

Another app that can also be used to educate anxious young people about the physiology of anxiety is the MindShift App.  Within this app is a list of physiological symptoms as well as education on the flight or fight response.  Both of these apps are available for Apple and Android devices.