Sexual Arousal

Master’s and Johnson’s Four Phases of Sexual Arousal is a model that explains the different stages our body cycles through on our way to a sexual climax.

The Excitement Phase is the first stage of the process.  When we encounter something that excites us sexually, messages are transmitted to the portion of the brain dedicated to sexual response.  The brain is flooded with endorphins making us think that whatever is causing the sexual arousal is very exciting and enjoyable and should be continued.

As the physical or psychological stimulation continues, our excitement is typically followed by erection. The brain sends a message that causes blood to flow into the spongy bodies in the penis. At the same time, flaps in the veins leading out of the penis enlarge, cutting off the drainage. As a result, the penis fills with blood. Finally, veins in the penis are compressed from the increasing pressure from the erection itself. Our heart rate and blood pressure also increase and the pressure of blood into the penis increases, keeping the penis hard.

In the Plateau Phase, the glans of the penis increases in size, and a few drops of pre-ejaculatory fluid may appear on the head of the penis. Most men will produce pre-ejaculate when anything considered to be sexually exciting occurs. There is no limit to the length of time we can prolong being aroused, and we can continue to produce drops of pre-ejaculate the whole time.

As the penis becomes increasingly erect, the nerve endings located there gradually become more and more sensitive to touch. As the erection grows, our heart and breathing rate increases. The testicles change as well, increasing in size by up to 50% as they also fill with blood. They become harder and are drawn up to the body as the point of ejaculation becomes nearer and nearer.

All of the sections of the erect penis are not equally sensitive. By varying locations being stimulated, we can delay orgasm and intensify our pleasure. Stimulation of the base of the penis, near the body, while pleasant, normally will not be sufficient to achieve orgasm. The underside of the tip of the penis, called the “frenulum”, is very sensitive to manual stimulation. The glans (head) of his penis gets wider and the blood vessels in and around the penis fill with blood. A warm feeling around the perineum (area between the testicles and anus) develops. Our heart rate increases, blood pressure rises, breathing becomes even quicker, and the muscles in our thighs and buttocks begin tighten. We’re getting close to orgasm.

Many men consider the Orgasm Phase to be the same as ejaculation. This is not the case.  Orgasm & ejaculation are actually separate events, although they seem to occur simultaneously. One can happen without the other. Orgasm is the mental and emotional state—the peak feeling that can send shudders throughout the body.  Ejaculation is the physical response—the expulsion of fluid.

It’s pretty amazing all the things that happen during an ejaculation. Ejaculation is actually a two-stage process.  First, there’s emission, where the semen moves out from the seminal vesicles into the base of the penis. Next is propulsion, where the semen leaves the meatus of the penis and is propelled out.

During the emission phase, the muscles of the vas deferens contract more to propel sperm towards the prostate. Secretions emitted from contractions of both the seminal vesicles and prostate combine with the contents of the vas deferens as they come together in the base of the penis. These fluids combine to form semen. Pressure builds in the prostate. Then the bladder sphincter closes—preventing semen from going into the bladder. At this point, a man gets that familiar sense of ejaculatory inevitability—most men recognize this place as the point of no return—you are going to cum and there’s nothing that will stop it.

This is when the propulsion phase takes over. The powerful ejaculation of semen is mediated by nerve complexes in the spine, stimulated by the sensory nerve endings of the penis responding to friction on the touch receptors of the penis. Then the rhythmic wavelike soft-muscle contractions of your PC muscle (remember Kegels?) propel the semen down your urethra and out.

With practice, a man can learn a degree of control over the point when he proceeds to orgasm and ejaculation. Some men believe that male orgasm invariably results in ejaculation, but this is not always true. Some men have learned techniques for having multiple orgasms without ejaculating. Many of these techniques involving squeezing of the urethra such that the semen is not allowed to leave the body.

In the Resolution Phase, the valves which had maintained the erection, open and the penis drains of blood returning to its flaccid state.  Ordinarily our interest in sexual activity of any kind decreases significantly for a period that lasts anywhere from a few minutes to several days. The generally pleasant feelings of satiety, lack of interest in further sexual activity and sleepiness following the male orgasm (which many of our sexual partners do not appear to fully understand or appreciate) are primarily linked to a chemical called oxytocin that is released during orgasm.