Emission is accomplished by contraction of the vas deferens, seminal vesicles, and ejaculatory ducts. This process is under adrenaline control. Ejection results from the rhythmic contractions of the muscles around the urethra, which causes the forcible ejection of the ejaculate. Within the spinal cord lies the ejaculation center which is the area involved in the coordination of signals from the brain and penis that eventually lead to ejaculation.
In normal men there exists a linear sexual response cycle: desire, arousal, plateau, orgasm, and resolution.
Orgasm can be subdivided into climax and ejaculation. During the resolution phase it is normal for men to experience a refractory period; during the refractory period it is not possible to stimulate the penis back into the erect state. The refractory period is typically very brief in young men but becomes progressively longer with age.
There are four main ejaculatory disorders that are seen in clinical practice: (i) premature ejaculation, (ii) retrograde ejaculation, (iii) delayed ejaculation (orgasm), and (iv) anorgasmia.