Because of the chemical nature of impulse and the axon-dendrite structure. Because of the chemical nature of impulse and the axon-dendrite structure. http://www.biologymad.com/nervoussystem/nerveimpulses.htm (Best technical explanation and excellent graphics and animations)
Newborns may sneeze, and this is typically attributed to the irritation of their nasal passages. The most common irritants, explains Dr. Iannelli, are smoke (and simply smoking outside is not enough), animal dander from pets in the house, dust mites, and mold.
Sneezes happen when your body is trying to expel an irritant from the nasal cavity. If you have allergies, pollen or pet dander is usually to blame. If you have a cold, your body makes mucus to trap the virus, and sneezing helps force it (and the sickness) out of your body.