"Viagra does not cause a man to be sexually stimulated. Viagra is only in effect if a man is sexually stimulated. Understanding how it works, an individual must understand the method of how a man gets an erection. When a man is sexually aroused, the nervous system in the erectile tissue of his penis releases nitric oxide (NO). The nitric oxide stimulates an enzyme that produces something called a messenger cyclic guanosine monophosphate (cGMP). The cGMP relaxes the smooth muscle cells. One result of this is that the arteries in a man’s penis expand and the blood can flow into a man’s penis more easily. One other result is that the erectile tissue itself fills with blood. These processes result in an erection. Viagra works by retaining the level
