An orgasm (sexual climax) is the conclusion of the plateau phase of the sexual response cycle, and may be experienced by both males and females. Orgasm is characterized by intense physical pleasure, controlled by the involuntary, or autonomic, nervous system. It is accompanied by quick cycles of muscle contraction in the lower pelvic muscles, which surround the primary sexual organs and the anus. Orgasms are often associated with other involuntary actions, including muscular spasms in other areas of the body, a general euphoric sensation, and frequently, vocalizations.

Post orgasm is often experienced as relaxing, which is attributed to the release of prolactin. Male and female brains demonstrate similar changes during orgasm, with brain scans showing a temporary reduction in the activity of large parts of the cerebral cortex.

Achieving orgasm

One of the main ways of achieving orgasm is by direct or indirect stimulation of the penis or clitoris. Such stimulation can come from a variety of activities, including but not limited to sexual intercourse, manual masturbation, anal sex, oral sex, non-penetrative sex, a sensual vibrator, or an erotic electrostimulation. Orgasm may also be achieved by stimulation of the nipples or other erogenous zones. In the absence of physical stimulation, orgasm can be from psychological arousal alone, or during dreaming (a nocturnal emission or "wet dream" in males).

Important in sexual stimulation are internal glands, called the Skene's glands in women and the prostate in men, two homologous structures. In common use, the term G-spot refers to these areas.

The stimulation can come from receptive intercourse, fingering, fisting, or penetration with a dildo.

With sufficient stimulation, the prostatic structure can also be "milked." Providing that there is no simultaneous stimulation of the penis, prostate milking can cause ejaculation without orgasm. When combined with penile stimulation, some men report that prostate stimulation increases the volume of their ejaculation.

Vaginal orgasm

The female body can achieve orgasm from stimulation of the clitoris and from stimulation of the G-spot. The Gräfenberg spot, or G-spot, is a small area behind the female pubic bone surrounding the urethra and accessible through the anterior wall of the vagina. The G-spot orgasm is sometimes referred to as "vaginal," because it results from stimulation inside the vagina, including during sexual intercourse.

The "two-orgasm theory" (the belief that in women there is a vaginal orgasm and a clitoral orgasm), has been criticized by feminists such as Ellen Ross and Rayna Rapp as a "transparently male perception of the female body". The concept of purely vaginal orgasm was first postulated

In 1966, Masters and Johnson published pivotal research about the phases of sexual stimulation. Their work included women and men, and unlike Alfred Kinsey earlier (in 1948 and 1953), tried to determine the physiological stages before and after orgasm. One of the results was the promotion of the idea that vaginal and clitoral orgasms follow the same stages of physical response. Masters and Johnson also argued that clitoral stimulation is the primary source of orgasms.