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How Orgasms Work

        Health | Sexuality

Anatomy of an Orgasm
After orgasm comes resolution and relaxation.
After orgasm comes resolution and relaxation.
George Doyle/Getty Images

In their 1966 book "Human Sexual Response," Masters and Johnson divided the sexual response cycle into four phases: excitement, plateau, orgasm and resolution [source: Bolin and Whelehan]. Boiling down one of humans' most subjective physiological experiences to a discrete flowchart attracted criticism in subsequent decades, but the phases still offer an instructive framework for describing how orgasms generally happen inside the body.

Although differences between male and female orgasms abound, both share similar respiratory, circulatory and muscular hallmarks. Sexual excitement in the brain stimulates increased blood flow to the genitals, engorging the penis in men and enlarging and lubricating the clitoris and labia in women. Pulses quicken, and the elevated heartbeats are heard in more intensive inhalations. Central nervous systems fully engage, directing messages of escalating enjoyment along the pelvic, pudendal and hypogastric nerve endings in the genital regions back to the brain's reward system and vice versa during plateau [source: Nuzzo]. This full-body workout then crests with a series of pelvic, cervical and anal muscle contractions in 0.8-second increments that correspond with orgasmic sensations and ejaculation [source: Elliott]. Deep relaxation and resolution typically follow as muscles relax and heart rates slow to a resting pace.

You can easily visualize the clinical description of an orgasm as an "explosive cerebrally encoded neuromuscular response" by watching the brain conduct and react to orgasms via functional MRI (fMRI) screening [source: Komisaruk, Beyer and Whipple]. In one experiment involving participants stimulating themselves to climax, the experience energized more than 30 discrete places in the brain [source: Sukel]. For instance, the nucleus accumbens and ventral tegmental area work in tandem to open the floodgates of pleasure-prompting dopamine, while the pituitary gland pumps out oxytocin, a hormone that mediates bonding [source: Freeman].

As men and women close in on the grand finale, their orgasmic brain activity appears strikingly similar on PET scans, save a couple telling distinctions [source: Georgiadis]. In female brains, orgasms flip off the lateral orbitofrontal cortex, a mechanism located behind the left eye that promotes self-evaluation [source: Portner]. In male brains, activity in the amygdala slows during coitus, dampening aggressive instincts [source: Portner]. But when sexologists move away from mechanics and compare frequency, subjective sensation and environmental components that contribute to orgasms, they quickly encounter distinct biological divides.


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