orgasm

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.
sensation
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,[40] but most men agree that it is highly pleasurable.
in women
recently, researchers from the university medical center of groningen, the netherlands, correlated the sensation of orgasm with muscular contractions occurring at a frequency of 8–13 hz centered in the pelvis and measured in the anus. they argue that the presence of this particular frequency of contractions can distinguish between voluntary contraction of these muscles and spontaneous involuntary contractions, and appears to more accurately correlate with orgasm as opposed to other metrics like heart rate that only measure excitation. they claim to have identified "[t]he first objective and quantitative measure that has a strong correspondence with the subjective experience that orgasm ultimately is". they note that the measure of contractions that occur at a frequency of 8–13 hz is specific to orgasm. they found that using this metric they could distinguish from rest, voluntary muscular contractions, and even unsuccessful orgasm attempts.[43]
orgasm and the brain
there have been very few studies correlating orgasm and brain activity in real time, owing to cultural barriers and technical difficulties. however a series of studies conducted by gert holstege and his colleagues at the university of groningen in the netherlands have established physiological characteristics which are unique to orgasm, including brain activity, as well as variation in the responses between men and women.
one study examined 12 healthy women using a positron emission tomography (pet) scanner while they were being stimulated by their partners. brain changes were observed and compared between states of rest, sexual stimulation, faked orgasm, and actual orgasm. " differences were reported on the brain changes associated with men and women during stimulation. however the same changes in brain activity were observed in both sexes in which the brain regions associated with behavioral control, fear and anxiety shut down. regarding these changes, holstege said in an interview with the london times, "what this means is that deactivation, letting go of all fear and anxiety, might be the most important thing, even necessary, to have an orgasm."[44]
during stroking of the clitoris, the parts of the female brain responsible for processing fear, anxiety and behavioral control start to relax and reduce in activity. this reaches a peak at orgasm when the female brain’s emotion centers are effectively closed down to produce an almost trance-like state. holstege is quoted as saying, at the 2005 meeting of the european society for human reproduction and development: "at the moment of orgasm, women do not have any emotional feelings." [45]
initial reports indicated it was difficult to observe the effects of orgasm on men using pet scan, because the duration of male orgasm was much shorter. however, a subsequent report by rudie kortekaas, et. al. noted, “gender commonalities were most evident during orgasm… from these results, we conclude that during the sexual act, differential brain responses across genders are principally related to the stimulatory (plateau) phase and not to the orgasmic phase itself.” [3]
orgasm and health
orgasm, and indeed sex as a whole, are physical activities that can require exertion of many major bodily systems. a 1997 study in the british medical journal[46] based upon 918 men age 45-59 found that after a ten year follow-up, men who had fewer orgasms were twice as likely to die of any cause as those having two or more orgasms a week. a follow-up in 2001 which focused more specifically on cardiovascular health found that having sex three or more times a week was associated with a 50% reduction in the risk of heart attack or stroke. (note that as a rule, correlation does not imply causation).
orgasmic dysfunction
the inability to have orgasm is called anorgasmia, ejaculatory anhedonia, or inorgasmia. if a male experiences erection and ejaculation but no orgasm, he is said to have sexual anhedonia.
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.[citation needed]
specifically in relation to simultaneous orgasm and similar practices, many sexologists claim that the problem of premature ejaculation[47] 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.
drugs and orgasm
certain drugs have been reported to have enhancing effects on orgasm. nitrite inhalants are used by both men and women to enhance orgasm. ghb, gbl and 1,4 butanediol are commonly used to enhance orgasms. cocaine also increases sexual desire while delaying orgasm.[48] both male and female users of stimulants, such as 3,4-mdma (ecstasy), amphetamines, and psychedelics like lsd, psilocybin-containing mushrooms, and marihuana sometimes report heightened sexual pleasure. throughout history, recreational drugs have been used to enhance orgasm[49] but, due to lack of research (or government-mandated research restrictions), may be unreliable or have hazardous side effects. anecdotal evidence suggests that women have enhanced orgasms with sildenafil (commercially known as viagra).[citation needed]
in tantric sex

neotantra is the ancient indian spiritual tradition of sexual practices. it attributes a different value to orgasm than traditional cultural approaches to sexuality. some practitioners of tantric sex aim to eliminate orgasm from sexual intercourse by remaining for a long time in the pre-orgasmic and non-emission state. advocates of this, such as rajneesh, claim that it eventually causes orgasmic feelings to spread out to all of one's conscious experience.[50][51]
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.[52]
these practices should not be confused with buddhist tantra (vajrayana).
in other animals

see also: animal sexuality
the mechanics of male orgasm are similar in most mammals. females of some mammal and some non-mammal species such as alligators[53] 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.[54]
in literature

jupiter and juno, by annibale carracci.
the orgasm has been widely represented in the literature over the centuries. in antiquity, latin literature addressed the subject as much as the greek literature: ovid's metamorphoses tells in book iii a discussion between jove and juno, in which the first of two states: "the sense of pleasure in the male is farmore dull and dead, than what you females share."[55] juno refuses this idea; both, therefore, agree investigate the opinion of tiresias ("who had known venus/love in both ways").[56] by giving reason to the words of jove, tiresias is punished by juno that hurt, blinded the eyes of the prophet of aonia.[57] preterite, in the didact ars amatoria, ovid advises male to advance on its object of seduction and adds that there is nothing better than a man and a woman lying finish and dull next to each other, having