03/04/2015
Under normal circumstances, when a man is s*xually stimulated, his brain sends a message down the spinal cord and into the nerves of the p***s. The nerve endings in the p***s release chemical messengers, called neurotransmitters, that signal the arteries that supply blood to the corpora cavernosa (the two spongy rods of tissue that span the length of the p***s) to relax and fill with blood. As they expand, the corpora cavernosa close off other veins that would normally drain blood from the p***s. As the p***s becomes engorged with blood, it enlarges and stiffens, causing an er****on. Problems with blood vessels, nerves, or tissues of the p***s can interfere with an er****on.