Stimulation of the genital and perineal area can cause the "genital reflex" (erection and ejaculation in the male, vaginal changes and lubrication in the female). This reflex is mediated by the lower spinal cord, and the brain need not be involved.

The process of ejaculation is basically a reflex phenomenon. The afferent impulses arise chiefly in the sense organs of the glans and are transmitted by the internal pudendal nerves to the spinal cord. Efferent impulses leaves the upper lombar segments of the spinal cord, travel over the lumbar rami communicantes and hypogastric nerves through the hypogastric plexus and evoke emission. The impulses that provoke ejaculation are parasympathetic and travel over the internal pudendal nerves.

Author: Dr. Silvia Helena Cardoso, PhD. Psychobiologist, master and doctor in Sciences by the University of São Paulo and post doctoral fellowship by the University of California, Los Angeles. Invited Professor and Associate Researcher of the Center for Biomedical Informatics, State University of Campinas (Unicamp), Brazil. Email: