The completion of sexual responses depends on the regulation of the nervous and endocrine systems. The nervous system's regulation of sexual responses is primarily reflexive. The primary center is located in the lumbosacral spinal cord. Stimuli from the genitals or other sexually sensitive areas are transmitted to the primary center via sensory nerves and then sent via efferent nerves to the sexual organs, resulting in sexual arousal.
The secondary center is located in the hypothalamus and pituitary gland. The hypothalamus not only exerts direct regulatory effects on the spinal centers below it but also participates in the regulation of sexual responses by controlling the secretion of various pituitary hormones from the anterior and posterior pituitary.
The tertiary or highest center, located in the cerebral cortex and limbic system, includes regions such as the cingulate gyrus, hippocampus, nucleus accumbens, and amygdala. The cerebral cortex processes nerve impulses received from peripheral sensory organs and lower centers, integrating this information to generate arousal or inhibition of sexual response. The human brain is capable of receiving sexual stimuli not only through sensory channels such as touch, vision, hearing, smell, and taste but also through internally generated psychological activities such as sexual fantasies and memories. These psychological processes may lead to sexual arousal and even orgasm.
Unconditioned stimuli are primarily mediated by reflex responses through the lower spinal centers, whereas conditioned stimuli involve the higher cortical centers of the brain. Research suggests that the brain contains two key regulatory centers: a dopamine-responsive center that promotes sexual response and a serotonin-inhibitory center that suppresses it. The balance between these two centers regulates sexual responses. When the dopamine-responsive center is activated, downstream signals are initiated, triggering reproductive tract responses through spinal reflex circuits.
In addition to neural regulation, sex hormones play a crucial role in the modulation of female sexual responses. Among these, androgens are the most important hormones for regulating female sexual response. They can activate the central dopamine-responsive center and induce relaxation of the smooth muscles in genital blood vessels by promoting nitric oxide synthesis.
Estrogens and progestogens are essential for the differentiation, maturation, and functional maintenance of the female reproductive system. Estrogens promote sexual arousal by facilitating the release of various neuropeptides in the hypothalamus, lowering sensory thresholds through enhanced neurotransmission, increasing pelvic blood flow, and promoting the transudation of fluid from vaginal mucosa. At certain ratios of estrogen to progestogen, progestogen may exert an inhibitory effect on female sexual responses.