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).
This version of the Kindle runs the older Android 2.3 (Gingerbread) by default; a special version customized specifically by Amazon called Fire OS.. I mentioned in my article that it is possible to install a full version of the Android operating system on the Kindle Fire to add even more capabilities.