Physiology of sexual intercourse
The physiological phases of the sexual response cycle include: sex drive, sexual arousal, orgasm, and resolution phase.
The cortex and subcortical formations of the brain, as well as the reproductive centers of the spinal cord, participate in the regulation of human sexual function. All sexual centers are interconnected, are in interaction and subordination, form a single system.
Sexual attraction (libido) depends on the secretory activity of the endocrine glands (testes in men and ovaries in women, adrenal glands in both sexes), as well as metabolism. In addition, sex drive and orgasm can not be carried out without the participation of the brain.
In an adult, the level of excitability of the genital centers and the strength of sexual desire is determined by the level of hormones.
There is a dependence of libido on anthropological characteristics – brunettes have a stronger sex drive than blondes.
In undersized sex drive is stronger than in adults. A thin woman for her sexual satisfaction requires more effort and affection than a full one.
In countries with warm climates, sexual attraction is more intense. It follows that southerners and southerners are more temperamental than northerners and northerners.
The sexual excitability of men and women is different. In general, sexual arousal in a woman is lower than in a man. In a man, desire arises even before the onset of sexual intercourse, during coitus, excitement increases rapidly, erection also arises quickly, and with the onset of orgasm and ejaculation, excitement and erection completely disappear.
With excessive excitability of the reproductive centers, ejaculation occurs very quickly. Such a man is called low-potent. The reasons for this and methods of overcoming are described in the corresponding chapter. Impotence in men is a lack of an erection or a weak erection, insufficient to insert a penis into the vagina.
In addition to hormones and erotic caresses, stimulants of sexual function can also be the so-called key irritants, or releases.
In men, the releases are the appearance of the female genital organs, the perception of signs of sexual arousal of a woman, and touching her genitals. And negative stimuli (for example, an insulting remark of a woman, the presence of strangers) can inhibit this reaction.
Sexual arousal can be caused by visual, auditory, olfactory and other stimuli, that is, mental factors – the “sexy” appearance of the partner, preparation for sexual intimacy, as well as memories of sexual intimacy and erotic fantasies.
These irritants are individual in each person and are associated with his ideas, personal experience and ideals.
Music also has an erotic effect – firstly, by stimulating the deep structures of the brain, and secondly, by revitalizing memories, associations and various experiences.
Women are less likely to respond to the psychic effects of releases than men.
The appearance of attractive women in men causes sexual arousal twice as often as the appearance of attractive men in women.
The appearance of naked female genitalia excites a man, and the appearance of a man’s naked genital organs does not cause an erotic reaction in 50% of women, and for many this is even unpleasant and inhibits sexual arousal.
For many women, expectation of sexual intimacy does not cause sexual arousal, and a man experiences arousal during upcoming sexual contact.
That is, the nature of male and female sexuality varies significantly.
Sexual arousal arises not only under the influence of hormones and releasers, but also with mechanical irritation (other names – stimulation, erotic caresses), that is, touching the erogenous zones (from the Greek word “eros” love, passion) – especially sensitive to caresses body parts.
American sexologists W. Masters and V. Johnson in the dynamics of sexual arousal distinguish the phase of excitation, the plateau phase, the phase of orgasm and the phase of reverse development.
In the phase of sexual arousal in men, after 20-40 seconds from the onset of sexual stimulation, the rush of blood to the pelvic organs increases and their outflow is difficult due to narrowing of the veins. As a result of this, the penis begins to rapidly increase in volume (about 3 times), becomes hard and lengthens by 7-8 centimeters. He changes his position, rises – an erection occurs (from the Latin “erigere” – raise). With the onset of an erection, a man has a tendency to discharge from sexual tension.
If the nerve endings of the penis will experience rhythmic friction against the walls of the vagina during frictions, then the erection is enhanced, and sexual arousal increases. Shortness of breath and palpitations, redness of the face.
If the frictions stop, then the excitation begins to weaken gradually, the veins expand and the outflow of blood increases. The penis decreases in volume and becomes softer. If the frictions resume, then the erection is reinforced again.
Thus, experienced men, either stopping or renewing frictions, can prolong sexual intercourse (you will read more about this technique in the chapter on prolonging sexual intercourse).
A woman needs longer preparation for sexual intercourse and exposure to her erogenous zones, which will help her quickly achieve the desired degree of sexual arousal for taking the penis into the vagina.
There are women very temperamental, with high secretory activity of the ovaries, and they can be even more sensual than men.
However, it is more difficult for a woman with average sensuality to start sexual intercourse than a man, because without preliminary cares her genitals are not ready for copulation – the walls of the genital tube are almost adjacent to each other, there is no lubrication, there is no elasticity. The excitement of a woman is enhanced only when exposed to erogenous zones.
In the phase of excitement in women, the rush of blood to the genitals also intensifies. Small lips increase 2-3 times across, their color from pale pink becomes bright red. The clitoris swells – the organ of the female sexual sense – it increases one and a half to two times, becomes more dense. The excited vagina swells strongly, becomes “hot” due to the filling of its blood vessels with blood, its muscles contract, and it becomes narrower, which contributes to a closer contact with the penis during intercourse.
With sexual arousal, a woman’s genitals become wet, the vagina is covered with a lubricant that facilitates gliding of the penis (lubrication). Lubrication is formed due to the secretion of mucus by the large and small glands of the vestibule of the vagina, as well as due to sweating of fluid from the vaginal veins.
At rest, the walls of the vagina are almost tightly adjacent to each other, leaving only a small gap. With sexual arousal, the vagina lengthens and expands, the cervix and body of the uterus are pulled up and back. The diameter of the vagina near the cervix increases 2.5 to 3 times, which serves as a container for sperm. At this moment, there is no close contact between the penis and the walls of the vagina.
With increasing excitation, it reaches a high level and remains at this level for some time (plateau phase). In this phase, the vagina adapts to the size of the penis of a man. Both partners feel each other well. The front third of the vagina is filled with venous blood and narrows by 50% compared to the previous phase and becomes a narrow tube. Muscles tightly encircle the penis – this is called an orgasmic cuff. This provides a strong stimulation of the nerve endings in both partners.
In this phase, an increase in the volume of the mammary glands and an “erection” of the nipples occur – they are extended by 1 centimeter and increase in diameter by 0.25 – 0.5 centimeters.