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.
Sneezing can occur for a variety of reasons that have in common an irritation of the lining (mucous membranes) of the nose or throat. It is rarely a sign of a serious illness. Many environmental triggers can lead to sneezing, including air pollutants, pollen, dry air, and dust. Spicy foods can sometimes cause sneezing. Allergies, colds, and the flu are common causes of sneezing. Drug withdrawal, emotions, and certain medications are less common causes of sneezing. Some people may sneeze as a reaction to exposure to bright light (known as a photic sneeze reflex).