Science of mechanism of ejaculation
The physical process of ejaculation requires two sequential actions: emission and expulsion
The emission phase is the first phase. It involves deposition of seminal fluid from the ampullary vas deferens, seminal vesicles and prostate gland into posterior urethra. The second phase is the expulsion phase. It involves closure of bladder neck, followed by the rhythmic contractions of the urethra by pelvic-perineal and bulbospongiosus muscle, and intermittent relaxation of external urethral sphincters.
It is believed that the neurotransmitter serotonin (5HT) plays a central role in modulating ejaculation. Several animal studies have demonstrated its inhibitory effect on ejaculation. Therefore, it is perceived that low level of serotonin in the synaptic cleft in these specific areas in the brain could cause premature ejaculation. This theory is further supported by the proven effectiveness of selective serotonin reuptake inhibitors (SSRIs), which increase serotonin level in the synapse, in treating PE.
Sympathetic motor neurons control the emission phase of ejaculation reflex and expulsion phase is executed by somatic and autonomic motor neurons. These motor neurons are located in the thoracolumbar and lumbosacral spinal cord and are activated in a coordinated manner when sufficient sensory input to reach the ejaculatory threshold has entered the central nervous system.
Several areas in the brain, and especially the nucleus paragigantocellularis, have been identified to be involved in ejaculatory control. Scientists have long suspected a genetic link to certain forms of premature ejaculation. In one study, ninety-one percent of men who suffered from lifelong premature ejaculation also had a first-relative with lifelong premature ejaculation. Other researchers have noted that men who suffer from premature ejaculation have a faster neurological response in the pelvic muscles. Simple exercises commonly suggested by sex therapists can significantly improve ejaculatory control for men with premature ejaculation caused by neurological factors. Often, these men may benefit from anti-anxiety medication or SSRIs, such as sertraline or paroxetine, as these slow down ejaculation times. Some men prefer using anaesthetic creams, however, these creams may also deaden sensations in the man's partner, and are not generally recommended by sex therapists.
