Biomechanical phases of ejaculation [emission and expulsion] and the refractory period

Emission stage and the point of no return

The ejaculation of seminal fluid begins the moment nervous control shifts from the parasympathetic to the sympathetic nervous system.

This first biomechanical phase, called ejaculation, is triggered when erotic stimulation reaches a critical threshold.

During this stage, sympathetic fibers orchestrate the coordinated contraction of the muscular walls of the epididymis and the vas deferens, propelling the sperm toward the urethra.

Simultaneously, the seminal vesicles and the prostate contract their smooth muscles to release their secretions—rich in fructose, enzymes, and alkaline fluids—which constitute the majority of the semen’s volume.

The progressive accumulation of these fluids in the prostatic urethra generates internal pressure that psychologically translates into the sensation known as the point of ejaculatory inevitability.

At this precise moment, the person perceives that the physiological cascade has begun irreversibly, making it impossible to voluntarily stop the imminent expulsion of seminal plasma.

Mechanics of Ejection and Spinal Reflex

Once semen has accumulated in the urethra, the dilation of this duct triggers the second biomechanical phase, known as expulsion.

This physical stimulus activates a spinal reflex that sends immediate motor impulses through the pudendal nerve.

This neurological circuit triggers a series of involuntary, spasmodic, and rhythmic contractions in the striated muscles of the pelvic floor, notably the powerful action of the bulbospongiosus muscle.

These muscle contractions pump the seminal plasma, propelling it outward at high speed and pressure.

Although it is a mechanical event distinct from pleasure, ejaculation occurs synchronously with the cerebral orgasmic climax.

During this pleasurable peak, the brain releases large bursts of dopamine and endorphins, releasing all accumulated sexual tension.

Likewise, the pre-ejaculatory fluid from the bulbourethral glands helps lubricate the duct, allowing the semen to be expelled in a completely fluid, effective, rhythmic, and uninterrupted manner.

The Neurobiology of the Absolute Refractory Period

Following ejaculation and climax, the body enters a recovery phase known as the absolute refractory period.

During this period, the endocrine and central nervous systems radically alter their chemical balance through the massive secretion of prolactin and oxytocin, substances that temporarily block the neurotransmitter action of dopamine.

The presence of these hormones induces a gradual loss of penile rigidity and produces a deep, generalized state of satiety and somatic relaxation.

During this stage, which lasts anywhere from several minutes to several hours depending on the individual’s age and physical condition, the man is biologically incapable of responding to new erotic stimuli or achieving a new erection.

Scientific and educational understanding of this involuntary physiological pause dispels false expectations regarding inexhaustible physical performance and fully normalizes the somatic response following the complete expulsion of male seminal plasma from the human body.

Summary

Male ejaculation begins with the emission phase, which is under sympathetic control, during which sperm and glandular secretions accumulate in the urethra, reaching a pressure that produces the inevitable sensation of an impending climax.

Subsequently, the expulsion phase is triggered by a spinal reflex that activates rhythmic pelvic muscle contractions via the pudendal nerve, mechanically expelling semen in sync with the intense cerebral orgasmic discharge.

Finally, the body enters the absolute refractory period, during which the secretion of prolactin and oxytocin blocks dopamine, temporarily preventing a new erection and restoring somatic satiety and total male physiological rest.