The autonomic nervous system has two divisions: The sympathetic division acts to energize the body, preparing it for action. The parasympathetic division acts to calm the body, allowing it to rest. Our everyday activities are controlled by the interaction between the sympathetic and parasympathetic nervous systems.
Update: N2Aos is now available for Kindle Fire HD and Kindle Fire HD 8.9. And you get the full Android experience here, including access to the Google Play store and all the other features offered by Android 4.2 (excepting what's not available via hardware, of course).
A. Dietz says: If you have another android device you can sideload apps from Google Play to your Kindle Fire. Google How to sideload android apps to Kindle Fire for instructions. You can also go to other android app sites like getjar.com and download apps directly to your Kindle Fire.