In my very limited understanding, you are able to perceive smells because the molecules causing the smell fit into positions on the surface of receptor cells, much as a key fits into a lock. This in turn, generated a nerve impulse, which is sent to the brain.
My question: how long do the receptor cells keep the smell molecules locked in? How exactly are they discarded? Take the example of smelling something nastly (like decaying flesh)-you instinctively run away from such a smell. yet, the smell seems to stay with you for a long time-while the smell of a nice flower might last only seconds-why?