CPU temperature curiosity

When I run the game on standard textures and filtering, low shadows (off ingame), and no AA my cpu temperatures averaged higher than when I hiked the Textures to High with Very High filtering low shadows(off ingame) Depth of Field ON and 4xaa..

I imagine these things are graphics card related, but it was just sort of confusing to me and I was wondering if anyone knew why this would be happening.
At one point the latter settings were averaging 10 degrees Celsius lower..

Does the game at lower settings rely on your CPU and when you put certain settings higher does it shift from being CPU dependent to leaning a bit more on the GPU?
Sure the game didn't run as smoothly, but it wasn't quite the drop in performance that one would expect running the game on a laptop that is technically below minimum reqs

I run the game on an HP laptop
ATI radeon HD 4650m 1gb video ram (gddr3 I think)
T6600 @2.2ghz (C2D)
4 gigs of ram
Native 1366x768 but I only run the game @1280x768/720

It is same to presume when certain functions, like AA, are in use there are some software features that are not used. Since these features are not used while the GPU is providing processing power, your CPU temperature has a lower load.