Sexual Stimulation

Stimulation Sexual intercourse or other sexual activity can encompass various sexually stimulating factors (physiological stimulation or psychological stimulation), including different sex positions or the use of sex toys. Foreplay may precede some sexual activities, often leading to sexual arousal of the partners and resulting in the erection of the penis or natural lubrication of the vagina. It is also common for people to be as sexually satisfied by being kissed, touched erotically, or held as they are by sexual intercourse. In most mammals, the anatomy of the reproductive organs and some circuits of the nervous system are specifically organized for heterosexual copulation. Copulation corresponds to a succession of innate sexual reflexes: erection, vaginal lubrication, lordosis behavior, immobilization, intromission, pelvic thrust and ejaculation. These copulatory reflexes are controlled by hormones and facilitated by sexual pheromones. In hominidae, including humans, several biological factors that control copulation are modified. These changes in neurobiological control of copulation are particularly evident in females of hominidae. Non-primate females copulate only when in estrus, but sexual intercourse is possible at any time of the menstrual cycle for women. Sex pheromones facilitate copulatory reflexes, but, in humans, the detection of pheromones is impaired and they have only residual effects. Non-primate females put themselves in the crucial lordosis position and remain motionless, but these motor copulatory reflexes are no longer functional in women. Unlike mammalian copulation, where copulation is a reflex controlled by hormones and influenced by pheromones, human sexual intercourse is mostly a voluntary and learned activity that is performed in order to obtain sexual rewards (i.e., pleasure and/or procreation).

During coitus, the partners orient their hips to allow the penis to move back and forth in the vagina to cause friction, typically without fully removing the penis. In this way, they stimulate themselves and each other, often continuing until orgasm in either or both partners is achieved. For human females, stimulation of the clitoris plays a significant role in sexual activity; 70–80% of women require direct clitoral stimulation to achieve orgasm, though indirect clitoral stimulation (for example, via vaginal intercourse) may also be sufficient (see orgasm in females). Because of this, some couples may engage in the woman on top position or the coital alignment technique, a technique combining the "riding high" variation of the missionary position with pressure-counterpressure movements performed by each partner in rhythm with sexual penetration, to maximize clitoral stimulation. Anal sex involves stimulation of the anus, anal cavity, sphincter valve or rectum; it most commonly means the insertion of a man's penis into another person's rectum, but may also mean the use of sex toys or fingers to penetrate the anus, or oral sex on the anus (anilingus), or pegging. Oral sex consists of all the sexual activities that involve the use of the mouth and throat to stimulate genitalia or anus. It is sometimes performed to the exclusion of all other forms of sexual activity, and may include the ingestion or absorption of semen or vaginal fluids. Fingering (or digital penetration or digital intercourse) involves the manual manipulation of the clitoris, rest of the vulva, vagina or anus for the purpose of sexual arousal and sexual stimulation; it may constitute the entire sexual encounter or it may be part of mutual masturbation, foreplay or other sexual activities.