Liko,
I believe it is proper to approach this part of your pre-employment check with some apprehension. In fact if you were apprehensive enough so that "all" questions gave more or less the same 'physiological' feedback you would probably pass... that is the whole (to my understanding) concept of 'counter measures'... honest people 'show' little variations in the readings and that leaves the 'discerning' of a 'deception' completely up to the examiner (I'm sure that if that is not correct, others will flesh it out) which you don't really want. There are plenty of YouTube evidences of completely innocent people being called untruthful in (more or less) poly stings to demonstrate that the mind of the examiner has a lot to do with the results... not in intent but perhaps just a subjective leaning. If you can harness that anxiety "across the boards" you might have a better chance than 'just' being calm... I think.