Actually its like this :
Step 1:
The eyes will record the image of the naked supermodels with the room.
Step 2:
The brain will run the image over some overly complicated image and shape detection programs which will conclude the following:
You are in a room
There are nude female bodies present
Based on earlier knowledge recorded from print and digital media they are of supermodel attributes
Step 3:
Lower level functions of reproduction take effect and the brain redirects the flow of blood to your genitalia.
Step 4:
You twitter about your newly acquired state of arousal.
So overall i'd say everything except your ears are highly involved in the process, and irreplaceable.
