How the pressure in ANSYS is implemented?

There are several possibilities for the realization of the presure load.
For
example, when I apply a pressure to an area (lets say, thin rectangular
plate) the area of the plate grows during the deformation process. One
possibility is to keep the pressure per unit area constant (in this case
the total force acting on a plate grows during the deformation) and the
second is to keep constant the total force acting on the plate (in this
case the force per unit area decreases with the deformation). I looked
through the help, but I wasn't able to find which option is choosen in
ANSYS. I would appreciate any hints.