Many men have the experience of not being able to urinate after ejaculation, what is going on? This starts with the physiology of ejaculation. Ejaculation is regulated by the reflexes of the central nervous system, with impulses coming from penile sensory nerves, pubic nerves, sacral nerve roots and spinal cord afferents. After sexual stimulation, sympathetic excitation causes the smooth muscle of the vas deferens to contract and semen is discharged into the posterior urethra, while closing the internal urethral opening. Parasympathetic excitation causes the external urethral sphincter to relax and, in synergy with the perineal nerve, causes the sciatic spongiosus muscle and the bulbocavernosus muscle to produce rhythmic contractions, ejecting semen from the posterior urethra. The process of ejaculation is firstly the convergence of semen, where the secretions of the epididymis and vas deferens under sexual stimulation are driven into the posterior urethra, where they converge; secondly the surge of semen volume in the posterior urethra generates pressure on the area, which stimulates the spinal cord center and causes the bladder sphincter to close, which prevents the reflux of semen through the bladder neck and prevents the leakage of urine from the bladder. The reflexive efferent impulse from the sacral center excites the intrapubic nerves to the skeletal muscle fibers of the sciatic cavernous muscle and the bulbocavernosus muscle at the base of the penis, triggering a strong rhythmic contraction of the above muscle groups with an interval of about 0.8s, and the contraction generates a strong pressure to eject semen out of the body. Having said that, in fact, after ejaculation can not urinate, not seen a clear explanation, personal consideration may be the following reasons: 1, should not period: ejaculation muscle is in a state of tension, after ejaculation muscle relaxation, at this time the muscle is in a period of non-response to the command of urination. 2, spongy body compression: erection after ejaculation is not immediately weak, the spongy body is in a state of congestion, the filling of the spongy body compression of the urethra, so after ejaculation can not urinate, need to wait to adapt to a little. 3, bladder neck closure: the bladder sphincter is closed during ejaculation and still not completely open after ejaculation, resulting in urine not flowing out.