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.
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.
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 by Sigmund Freud. In 1905, Freud argued that clitoral orgasm was an adolescent phenomenon, and upon reaching puberty the proper response of mature women changes to vaginal orgasms. While Freud provided no evidence for this basic assumption, the consequences of the theory were greatly elaborated, partly because many women felt inadequate when they could not achieve orgasm via vaginal intercourse that involved little or no clitoral stimulation.
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.
Recent discoveries about the size of the clitoris show that it extends inside the body, around the vagina; this complicates or may invalidate attempts to distinguish clitoral vs. vaginal orgasms. Combined with the anatomical evidence that the internal part of the clitoris is a much larger organ than previously thought, these new discoveries could explain credible reports of orgasms in women who have undergone clitorectomy as part of female circumcision. The link between the clitoris and the vagina is evidence that the clitoris is the 'seat' of the female orgasm and is far more wide-spread than the visible part most people associate with it. But it is possible that some women have more extensive clitoral tissues and nerves than others, and so that some women can achieve orgasm only by direct stimulation of the external part of the clitoris.
In both sexes pleasure can be derived from the nerve endings around the anus and the anus itself. Hence, anal-oral contact can still be pleasurable without stimulation of the clitoris. Jack Morin has claimed that anal orgasm has nothing to do with the prostate orgasm, although the two are often confused.
The first orgasm of this type was reported among people who had spinal cord injury (SCI). Although SCI very often leads to loss of certain sensations and altered self-perception, a person with this disturbance is not deprived of sexual feelings such as sexual arousal and erotic desires. Thus some individuals are able to initiate orgasm by mere mental stimulation.
Some non-sexual activity may result in a spontaneous orgasm. The best example of such activity is a release of tension that unintentionally involves slight genital stimulation, like rubbing of the seat of the bicycle against genitals during riding, exercising, when pelvic muscles are tightened or when yawning or sneezing.
It was also discovered that some anti-depressant drugs may provoke spontaneous climax as a side effect. There is no accurate data for how many patients who were on treatment with antidepressant drugs experienced spontaneous orgasm, as most were unwilling to acknowledge the fact.
There are sensational reports of women having too many orgasms, including an unauthenticated claim that a young British woman has them constantly throughout the day, whenever she experiences the slightest vibration.
It is possible for a man to have an orgasm without ejaculation (dry orgasm) or to ejaculate without reaching orgasm. Some men have reported having multiple consecutive orgasms, particularly without ejaculation. Males who experience dry orgasms can often produce multiple orgasms, as the refractory period, is reduced. Some males are able to masturbate for hours at a time, achieving orgasm many times. In recent years, a number of books have described various techniques to achieve multiple orgasms. Most multi-orgasmic men (and their partners) report that refraining from ejaculation results in a far more energetic post-orgasm state. Additionally, some men have also reported that this can produce more powerful ejaculatory orgasms when they choose to have them.
One dangerous technique is to put pressure on the perineum, about halfway between the scrotum and the anus, just before ejaculating to prevent ejaculation. This can, however, lead to retrograde ejaculation, i.e. redirecting semen into the urinary bladder rather than through the urethra to the outside. It may also cause long term damage due to the pressure put on the nerves and blood vessels in the perineum. Men who have had prostate or bladder surgery, for whatever reason, may also experience dry orgasms because of retrograde ejaculation.
Other techniques are analogous to reports by multi-orgasmic women indicating that they must relax and "let go" to experience multiple orgasms. These techniques involve mental and physical controls over pre-ejaculatory vasocongestion and emissions, rather than ejaculatory contractions or forced retention as above. Anecdotally, successful implementation of these techniques can result in continuous or multiple "full-body" orgasms. Gentle digital stimulation of the prostate, seminal vesicles, and vas deferens provides erogenous pleasure that sustains intense emissions orgasms for some men. A dildo device (the Aneros) claims to stimulate the prostate and help men reach these kinds of orgasms.
Many men who began masturbation or other sexual activity prior to puberty report having been able to achieve multiple non-ejaculatory orgasms. Young male children are capable of having multiple orgasms due to the lack of refractory period until they reach their first ejaculation. In female children it is always possible, even after the onset of puberty. This capacity generally disappears in males with the subject's first ejaculation. Some evidence indicates that orgasms of men before puberty are qualitatively similar to the "normal" female experience of orgasm, suggesting that hormonal changes during puberty have a strong influence on the character of male orgasm.
A number of studies have pointed to the hormone prolactin as the likely cause of male refractory period. Because of this, there is currently an experimental interest in drugs which inhibit prolactin, such as cabergoline (also known as Cabeser, or Dostinex). Anecdotal reports on cabergoline suggest it may be able to eliminate the refractory period altogether, allowing men to experience multiple ejaculatory orgasms in rapid succession. At least one scientific study supports these claims. Cabergoline is a hormone-altering drug and has many potential side effects. It has not been approved for treating sexual dysfunction. Another possible reason may be an increased infusion of the hormone oxytocin. Furthermore, it is believed that the amount by which oxytocin is increased may affect the length of each refractory period.
A scientific study to successfully document natural, fully ejaculatory, multiple orgasms in an adult man was conducted at Rutgers University in 1995. During the study, six fully ejaculatory orgasms were experienced in 36 minutes, with no apparent refractory period. It can also be said that in some cases, the refractory period can be reduced or even eliminated through the course of puberty and on into adulthood. Later, P. Haake et al. observed a single male individual producing multiple orgasms without elevated prolactin response.
Orgasm is usually defined in a clinical context strictly by the muscular contractions involved.
In these and similar cases, the sensations experienced are subjective and do not necessarily involve the involuntary contractions characteristic of orgasm. However, the sensations in both sexes are extremely pleasurable and are often felt throughout the body, causing a mental state that is often described as transcendental, and with vasocongestion and associated pleasure comparable to that of a full contractionary orgasm.
For this reason, there are views on both sides as to whether these can be accurately defined as orgasms.
Morris also proposed that orgasm might facilitate conception by exhausting the female and keeping her horizontal, thus preventing the sperm from leaking out. This possibility, sometimes called the "Poleax Hypothesis" or the "Knockout Hypothesis," is now considered highly doubtful.
Other theories are based on the idea that the female orgasm might increase fertility. For example, the 30% reduction in size of the vagina could help clench onto the penis (much like, or perhaps caused by, the pubococcygeus muscles), which would make it more stimulating for the male (thus ensuring faster or more voluminous ejaculation). The British biologists Baker and Bellis have suggested that the female orgasm may have an "upsuck" action (similar to the esophagus' ability to swallow when upside down), resulting in the retaining of favorable sperm and making conception more likely. They posited a role of female orgasm in sperm competition.
A 1994 Learning Channel documentary on sex had fiber optic cameras inside the vagina of a woman while she had sexual intercourse. During her orgasm, her pelvic muscles contracted and her cervix repeatedly dipped into a pool of semen in the vaginal fornix, as if to ensure that sperm would proceed by the external orifice of the uterus, making conception more likely. Elisabeth Lloyd has criticized the accompanying narration of this film clip which describes it as an example of "Sperm Upsuck", saying that it depicted normal orgasmic uterine contractions, which have not been shown to have any effect on fertility.
The fact that women tend to reach orgasm more easily when they are ovulating suggests that it is tied to increasing fertility.
Other biologists surmise that the orgasm simply serves to motivate sex, thus increasing the rate of reproduction, which would be selected for during evolution. Since males typically reach orgasms faster than females, it potentially encourages a female's desire to engage in intercourse more frequently, increasing the likelihood of conception.
Science writer Natalie Angier has criticized this hypothesis as understating the psychosocial value of female orgasm. Catherine Blackledge in The Story of V, citing studies that indicate a possible connection between orgasm and successful conception, has criticized the hypothesis as ignoring the ongoing evolutionary advantages that result from successful conception. The anthropologist and primatologist Sarah Blaffer Hrdy has also criticized the argument that female orgasm as vestigial, writing that the idea smacked of sexism.
Evolutionary biologist Robin Baker argues in Sperm Wars that occurrence and timing of orgasms are all a part of the female body's unconscious strategy to collect and retain sperm from more evolutionarily fit men. An orgasm during intercourse functions as a bypass button to a woman's natural cervical filter against sperm and pathogens. An orgasm before functions to strengthen the filter.
Normally, as a man ages, the amount of semen he ejaculates diminishes, and so does the duration of orgasms. This does not normally affect the intensity of pleasure, but merely shortens the duration.
After ejaculation, a refractory period usually occurs, during which a man cannot achieve another orgasm. This can last anywhere from less than a minute to several hours, depending on age and other individual factors.
During orgasm, semen is usually ejaculated and may continue to be ejaculated for a few seconds after the euphoric sensation gradually tapers off. It is believed that the exact feeling of "orgasm" varies from one man to another, but most male human beings agree that it is highly pleasurable.
For a variety of reasons, some people choose to fake an orgasm. A recent Redbook survey shows that 52% of women regularly fake orgasms. Only 17% are likely to have an orgasm during sexual intercourse, because the clitoris often is not stimulated enough by intercourse alone. 43% of women report “some kind of sexual problem,” such as inability to achieve orgasm, boredom with sex, or total lack of interest in sex.
If orgasm is desired, anorgasmia is mainly attributed to an inability to relax, or "let go." It seems to be closely associated with performance pressure and an unwillingness to pursue pleasure, as separate from the other person's satisfaction. Often, women worry so much about the pleasure of their partner that they become anxious, which manifests as impatience with the delay of orgasm for them. This delay can lead to frustration of not reaching orgasmic sexual satisfaction. Psychoanalyst Wilhelm Reich, in his 1927 book The Function of the Orgasm was the first to make orgasm central to the concept of mental health, and defined neurosis in terms of blocks to having full orgasm. Although orgasm dysfunction can have psychological components, physiological factors often play a role. For instance, delayed orgasm or the inability to achieve orgasm is a common side effect of many medications.
Specifically in relation to simultaneous orgasm and similar practices, many sexologists claim that the problem of premature ejaculation is closely related to the idea encouraged by a scientific approach in early 20th century when mutual orgasm was overly emphasized as an objective and a sign of true sexual satisfaction in intimate relationships. A focus that is brought to the subject of simultaneous orgasm raises the problem that a man becomes too concerned with delaying ejaculation, which in fact deprives the intercourse from the necessary spontaneity and thus only making simultaneous orgasm even more difficult to reach. When partners become preoccupied with controlling and synchronizing their actions instead of enjoying the process, this may lead to sexual disturbance.
Some advocates of tantric and neotantric sex claim that Western culture focuses too much on the goal of climactic orgasm, which reduces our ability to have intense pleasure during other moments of the sexual experience. Eliminating this enables a richer, fuller and more intense connection.
These practices should not be confused with Buddhist tantra (Vajrayana).
The mechanics of male orgasm are similar in most mammals. Females of some mammal and some non-mammal species such as alligators have clitorises.
There has been ongoing research about the sexuality and orgasms of dolphins, a species which apparently engages in sexual intercourse for reasons other than procreation.
See Animal sexuality.