Neurophysiology of Erection and Ejaculation

Abstract

Introduction Penile erection and ejaculation are closely associated during sexual intercourse. Erection is a central psychoneuroendocrine and peripheral neuro-vasculo-tissular event, resulting in blood filling the sinusoidal spaces of the corpora cavernosa and corpus spongiosum. Ejaculation represents the climax of the sexual cycle and comprises emission (secretion of semen) and expulsion (propulsion of semen) phases. Aim This article provides an overview of the proposed neurophysiology of erection and ejaculation. Methods Review of the literature. Main Outcome Measures Current data on the neurophysiology of erection and ejaculation. Results In terms of peripheral innervation, the pelvic plexus represents a junction for efferent nerves to the structures involved in erection and ejaculation. At the spinal level, the spinal cord contains three sets of neurons (thoracolumbar sympathetic, sacral parasympathetic, and somatic) innervating the sexual organs involved in erection and ejaculation. The presence of cerebral descending pathways to spinal erection and ejaculation centers indicates that the brain has an excitatory or inhibitory effect on these processes. Brain structures that modulate spinal command of erection and ejaculation are part of a larger network that is dedicated to regulating sexual responses. Neurophysiological and pharmacological research has elucidated that dopamine and serotonin have central roles in modulating erection and ejaculation. Interestingly, erection is not a prerequisite for ejaculation, and each of these sexual responses can exist without the other. Conclusion Despite the association between erection and ejaculation during intercourse, these two processes can be considered distinct events from an anatomical, physiological, and pharmacological perspective.

Centrally mediated ejaculatory response via sympathetic outflow in rats: role of N‐methyl‐D‐aspartic acid receptors in paraventricular nucleus

“…Ejaculation commonly consists of two successive processes of emission and expulsion (Giuliano, 2011). The emission is characterized by the secretion of seminal fluids from the accessory sex gland and the closure of the bladder neck, and this phase is mainly activated by sympathetic neurons (Birowo et al, 2010).…”

“…The emission is characterized by the secretion of seminal fluids from the accessory sex gland and the closure of the bladder neck, and this phase is mainly activated by sympathetic neurons (Birowo et al, 2010). However, expulsion is the process of propelling spermatozoa from the prostatic urethra to the urethral meatus induced by rhythmic contractions of perineal striated muscles, which depend on the somatomotor system (Giuliano, 2011). The PVN is considered to be a center for neuroendocrine and autonomic integration, which involves appetite, body energy balance, blood pressure, heart rate, and sexual activity (Sakamoto, 2012).…”

Neural Control and Physiology of Sexual Function: Effect of Spinal Cord Injury

“…5 Since there is cerebral descending excitatory and inhibitory control over the pelvic innervations, sexual responses are modulated by minute-to-minute cerebral influences and neurotransmitter alterations. 18 The motor and sensory somatic control is via the pudendal nerve, and the 2 components of the autonomic system are via the pelvic nerve (sacral parasympathetic) and hypogastric nerve (thoracolumbar sympathetic).…”

“…Genital arousal requires dominance of parasympathetic output in the terminal nerve endings in erectile tissue in men and women over the tonic sympathetic tone (responsible for detumescence) through the pelvic nerve, a final common pathway, that receives inputs from the medial preoptic area and genitals. 5 With parasympathetic stimulation, proerectile neurotransmitters, particularly through the NO-cGMP pathway, promote smooth muscle relaxation and tumescence. However, the sympathetic nervous system also has a proerectile component, as demonstrated by lesions of the paravertebral sympathetic chain in humans and stimulation of the hypogastric nerve, and the sympathetic role may be "unmasked" following sacral spinal injury.…”

Polymorphic Variants of Neurotransmitter Receptor Genes May Affect Sexual Function in Aging Males: Data from the HALS Study

“…There are extensive data on associations between brain 5-HT and sexual function [26]. Generally, reduction of 5-HT function facilitates and enhancement inhibits sexual behavior in rodents [27].…”