The process of sexual arousal is a body-mind response triggered by any signal we interpret as erotic. These signals may be sensual – a touch, a smell, a visual cue – or they may have to do entirely with internal stimuli, such as a fantasy, memory, or sexual thought. Whatever the trigger, the process of arousal depends on chemical messengers known as neurotransmitters. These elements of the nervous system set into motion the physical changes we experience as sexual arousal.
There are two major components of physiological response. The first is vasocongestion, an increased flow of blood in various parts of the body. In men, the erect penis is the most obvious site of vasocongestion.
The second component of physiological response is a process by which neurotransmitters produce heightened levels of neuromuscular tension–more energy in the nerves and muscles. As a result of these two responses, we may experience heightened sensitivity anywhere from the fingertips to the lips to the genital organs.
The most widely used framework for understanding the workings of the body during a sexual encounter, known as the sexual response cycle, comes from the famous sex researchers William H. Masters, MD, a gynecologist, and Virginia E. Johnson, a psychologist. They describe the process by dividing it into four stages: excitement, plateau, orgasm, and resolution.
Heart rate and muscle tension increase. Nipples may become erect, and other parts of the body may become highly sensitive to touch. The most obvious early sign of arousal in men is erection, the process through which the penis becomes rigid enough for penetrative intercourse.
The testes, or testicles, are organs that play two critical functions in sex and reproduction. First, they set the stage for all male sexual activity by manufacturing the hormone testosterone, which at puberty triggers the development of the mature male body (e.g., deepening voice, increased muscle mass, broadening distribution of body hair). After puberty, testosterone helps to maintain sexual drive and distinctive male physical characteristics.
Second, the testes manufacture sperm, the male’s contribution to the reproductive process. A sperm cell is microscopic – approximately 0.05 millimeters long – and shaped like a tadpole, with a long tail. The tail enables a sperm cell to swim in vaginal fluids, up into the uterus, and finally up into a fallopian tube, where it fertilizes the egg. Sperm are produced in the testes at a rate of about 100 million a day and take about 70 days to mature. Sperm cells mature in the epididymis, tightly coiled tubing inside the testes. Sperm cells travel to the urethra through a canal called the vas deferens.
During the excitement stage of sexual response, the testes are drawn in more tightly to the body, and the scrotum, the sack of skin that holds the testes, becomes thicker and firmer.
Many sexual reflexes increase during the plateau phase. If stimulation continues – from kissing, caressing, penetration, or any other form of sex play – a man’s erection usually becomes more rigid. His testes become enlarged and are pulled up even closer to his body. Heart rate and blood pressure continue to rise, and muscular tension waxes. Researchers have also noted diminished hearing and vision in the plateau phase. About one-quarter of men experience what’s known as sex flush, pink or red blotches typically found around the breasts or elsewhere on the upper body.
Patterns of sexual arousal are highly variable, and a sexual encounter might last anywhere from a few minutes to an hour or more. The process is seldom a straight trajectory of escalating arousal and orgasm. Distractions, awkward positions, an uncomfortable touch–any of these can cause a momentary waning of pleasure or loss of erection. Sometimes sexual partners do not reach orgasm at all. Often, however, they recover quickly from these disruptions and continue stimulation until neuromuscular tension builds to the point where one or both reach the edge of orgasm. In men, this moment is marked by a point of no return called ejaculatory inevitability, meaning that the man is now certain to have an orgasm and to ejaculate.
Ejaculation is the expulsion of semen through the urethral opening at the tip of the penis. Semen is made up of sperm cells and secretions from the prostate gland, the two Cowper’s glands and the seminal vesicles. During the plateau phase, the Cowper’s glands secrete a clear fluid, which enters and lubricates the urethra. The prostate – a small, doughnut-shaped gland that surrounds the urethra where it joins the bladder – also secretes a fluid. At the threshold of orgasm, a series of contractions move this fluid to mix with secretions of the third key organ, the seminal vesicles. The seminal vesicles are, in effect, a basin. In this basin are joined the sperm that have traveled through the vas deferens and the secretions from the prostate and seminal vesicles. At orgasm, this mixture of sperm cells and fluids are expelled from the urethra, as semen, by series of contractions less than a second apart in the urethra and penis.
Yes. Some men can experience orgasmic contractions and whole-body pleasure without ejaculating, but it’s not common. Special exercises may be needed in order for a man to attain this extraordinary level of muscle control.
Some men can learn to have multiple orgasms, researchers say, by developing the ability to separate orgasm from ejaculation and have one or more climaxes before ejaculating. For most men, however, the postorgasmic resolution phase is also a refractory period, lasting at least a few minutes, during which they are unable to have another climax even if the penis is still erect and stimulation continues. Some experts say a small percentage of men have no refractory period and thus can be naturally multiorgasmic.
