When a man is exposed to certain stimuli -- either tactile or visual -- there are neurological signals, accompanied by a rush of blood flow, that are sent to the penis. When those signals reach the penis, the two erectile chambers located within the penis fill up with blood. This clamps off the side veins within the penis and traps blood in the erectile chambers. All of this occurs in response to the stimuli to which the man was exposed, causing an erection.

Erectile dysfunction is the persistent or consistent inability to sustain or maintain an erection. The majority of patients have some form of erectile dysfunction, but they vary in terms of the degree and the severity of their condition.

Here are answers to frequently asked questions about erectile dysfunction: