They play a very important role indeed. The first cranial nerve is the olfactory nerve. It is an entirely sensory nerve. There are specialised sensory receptive parts of the olfactory nerve which are located in the olfactory mucosa (a layer) of the upper parts of your nose. During breathing, air molecules attach to the olfactory mucosa and stimulate the olfactory receptors. Olfactory bulb cells then transmit electrical activity to other parts of the central nervous system via the olfactory tract. The smell that you are trying to identify is then interpreted by the brain. Thats why when you have a cold, you lose your sense of smell. The second cranial nerve is the optic nerve. The optic nerve starts from the cells of your retina inside your eye, where images that you see from the outside world are projected upside down. The cells then transmit the signals to your brain via the optic nerve. The optic nerve and tract has quite a complicated pathway. Anything that happens to this pathway (