Ejaculation is a reflex.
The functions of the prostate, the vasa deferentia and the seminal vesicles are triggered by excitation of the erogenous zones. Ejaculation is triggered by the release of the seminal fluid under the impact of this pressure. This mechanism, sketched very briefly here, is also influenced by chemical interactions which affect the speed of the ejaculation process. The parasympathetic action must be stronger than that of the orthosympathetic system if ejaculation control is to be achieved. But those few seconds are crucial to ejaculation control.