Changing where Microsoft Security essentials looks for definition updates

Where does MSE look for definitions by default?

Looking in the registry I see this:

Looking at the FallbackOrder value I see "MicrosoftUpdateServer|MMPC".

Does this mean it first checks a WSUS server (does that include internal WSUS servers?) and then falls back to MMPC which goes out to Microsoft's public distribution point?

If I have a WSUS server will MSE use this server to get definitions by default?

Also is there a way to point MSE clients to a UNC path for definition updates?

Thanks for any assitance.