Mechanism of penile erection

Sexual stimuli (tactile, visual, olfactory, and imaginative) are processed and integrated in the central nervous system which then activates certain autonomic and somatic pathways within the peripheral nervous system. This coordinated activation of the central and peripheral nervous systems leads to penile erection which is actually a result of relaxation of vascular and cavernosal smooth muscle in the penis. In the flaccid (detumescent) penis, the smooth muscle tone is heightened. Penile erection (tumescence) requires a decrease in the smooth muscle tone. The tone of the penile smooth muscle therefore is the main determinant of erectile function. In this chapter, the current information on the control of erectile function by this central-peripheral-smooth muscle axis will be reviewed.