Orgasm

# Overview
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.
After orgasm, humans often feel tired and a need to rest. This is attributed to the release of prolactin. Prolactin is a typical neuroendocrine response in depressed mood and irritation.
Ongoing research at the University Medical Center of Groningen, the Netherlands, studies brain events that accompany orgasm in men and women. Techniques used involve Positron Emission Tomography (PET) and fMRI. Male and female brains act almost the same during orgasm. Brain scans showed that large parts of the cerebral cortex temporarily reduced their activity.

# From the erectile organ
Orgasm is achieved after direct stimulation of the penis or clitoris for a period of time. This stimulation can be caused by sexual intercourse, manual masturbation, anal sex, oral sex, non-penetrative sex, a sensual vibrator, or an erotic electrostimulation. Any sexual stimulation of the penis or clitoris may eventually result in an orgasm; it may also be achieved by stimulation of other erogenous zones, in the absence of physical stimulation through psychological arousal and as a nocturnal emission or "wet dream".

## Multiple orgasms
In some cases, women either do not have a refractory period or have a very short one and thus can experience a second orgasm, and perhaps further ones, soon after the first. After the first, subsequent climaxes may be stronger or more pleasurable as the stimulation accumulates. For some women, their clitoris and nipples are very sensitive after climax, making additional stimulation initially painful.
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.

## Spontaneous orgasms
Orgasms can be spontaneous, seeming to occur with no direct stimulation. Occasionally, orgasms can occur during sexual dreams.
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.

# From the prostatic structure
Some people are able to achieve orgasm through stimulation of the prostatic structure, which in men is the prostate and in women is Skene's glands; in women the location of Skenes's glands is often known as the g-spot, or Grafenberg Spot, after the physician who first identified the spot as having orgasmic potential. The stimulation can come from receptive intercourse, fingering, fisting, or penetration with a dildo.
Orgasms of this kind can cause male orgasm and ejaculation. Women do not have prostate glands, therefore can not have a prostatic orgasm. 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 prostatic structure produces a secretion that forms one of the components of ejaculate; in males sperm are transmitted up the vas deferens from the testicles, into the prostate gland as well as through the seminal vesicles to produce what we know as semen.  Semen is expelled through the base of the penis out by contractions from the sphinctre and prostate, thus causing an orgasm.
Prostatic orgasms can be very pleasurable.  It can cause numbness through out the entire body causing emphasis on the thighs, mid back, and head of penis.  After a prostatic orgasm the body is very sensitive to touch and stimulation and may cause sleepiness.

# Other known categorizations of orgasm
Certain types and categorization of orgasm have become widely enough acknowledged to be discussed as distinctive forms of orgasm.

## Vaginal orgasm
The female body can achieve orgasm from stimulation of the clitoris and from stimulation of the G-spot. The Grafenberg 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. Many scientists believe that only certain women possess a G-spot. The G-spot orgasm is sometimes referred to as "vaginal," because it results from stimulation inside the vagina, including during sexual intercourse. However, only stimulation of the G-spot, and not other intravaginal stimulation, results in a "vaginal orgasm." The same is true for men, who are believed to have a male G-spot, through stimulation of the prostatic structure, which in men is the prostate. This leads to a different type of male orgasm than the orgasm that results from stimulation of the penis.
The "two-orgasm theory" (the belief that in females 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. Freud's claims about this and many other biological subjects, were later largely proven false or based on supposition.
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 - it extends inside the body, around the vagina - complicate or may invalidate attempts to distinguish clitoral vs. vaginal orgasms. Recent anatomical research shows that there are nerves connecting intravaginal tissues and the clitoris.  This, with the anatomical evidence that the internal part of the clitoris is a much larger organ than previously thought, 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.

## Anal orgasm
Anal orgasm is an orgasm brought on by anal stimulation, such as from anal sex, an inserted finger, or a sex toy. Some men are able to achieve an anal orgasm.
A woman may come to orgasm without stimulating the anus, by stimulation of the buttocks and anal cleft with the tongue. But typically, stimulation of the G-spot through the wall shared between the vagina and the rectum, from a sex toy, finger or a penis, may bring about an orgasm. This is often greatly facilitated through additional manual stimulation of the clitoris. Another theory on the source of anal orgasm in the female is the perineal sponge. The perineal sponge is an erectile structure located between the vagina and rectum that responds to stimulation like any other erectile tissue. Anecdotal evidence suggests that some women experience anal orgasm as qualitatively different from clitoral or vaginal orgasm, though for many others the distinction is less clear.
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. Anal orgasm has nothing to do with the prostate orgasm, although the two are often confused.

## Breast orgasm
A breast orgasm is a female orgasm that is triggered from the stimulation of a woman's breast. Not all women experience this effect when the breasts are stimulated; however, some women claim that the stimulation of the breast area during sexual intercourse and foreplay, or just the simple act of having their breasts fondled, has created mild to intense orgasms. According to one study that questioned 213 women, 29% of them had experienced a breast orgasm at one time or another, This shows that it is not common, but it is possible. An orgasm is believed to occur in part because of the hormone oxytocin, which is produced in the body during sexual excitement and arousal. It has also been shown that oxytocin is produced when an individual's nipples are stimulated and become erect.

# Other definitions of "Orgasm"
There is some debate whether certain types of sexual sensation should be accurately classified as 'orgasm', including female orgasms caused by G-spot stimulation alone, and the demonstration of extended or continuous orgasms lasting several minutes or even an hour. The question centers around clinical definition of orgasm.
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.

# Evolutionary function of orgasms
Most male orgasms expel sperm from the body during vaginal intercourse, which can result in conception. Evolutionary biologists have several hypotheses about the role, if any, of the female orgasm in the reproductive process. In 1967, Desmond Morris first suggested in his popular-science book The Naked Ape that female orgasm evolved to encourage physical intimacy with a male partner and help reinforce the pair bond. Morris suggested that the relative difficulty in achieving female orgasm, in comparison to the male's, might be favorable in Darwinian evolution by leading the female to select mates who bear qualities like patience, care, imagination, intelligence, as opposed to qualities like size and aggression, which pertain to mate selection in other primates. Such advantageous qualities thereby become accentuated within the species, driven by the differences between male and female orgasm. If males were motivated by, and taken to the point of, orgasm in the same way as females, those advantageous qualities would not be needed, since self-interest would be enough.
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 1997 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 dipped into a pool of semen in the vagina 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.

## Female orgasm as vestigial
The clitoris is homologous to the penis; that is, they both develop from the same embryonic structure. Stephen Jay Gould and other researchers have claimed that the clitoris is vestigial in females, and that female orgasm serves no particular evolutionary function. Proponents of this hypothesis, such as Dr. Elisabeth Lloyd, point to the relative difficulty of achieving female orgasm through vaginal sex, the limited evidence for increased fertility after orgasm and the lack of statistical correlation between the capacity of a woman to orgasm and the likelihood that she will engage in intercourse.
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.

## Genetic basis of individual variation
A 2005 twin study found that one in three women reported never or seldom achieving orgasm during intercourse, and only one in ten always orgasmed. This variation in ability to orgasm, generally thought to be psychosocial, was found to be 34% to 45% genetic. The study, examining 4000 women, was published in Biology letters, a Royal Society journal. Dr. Elisabeth Lloyd has cited this as evidence for her Fantastic Bonus Theory.

# Medical aspects of orgasm

## Physiological responses

### In male humans
During orgasm, a human male experiences rapid, rhythmic contractions of the anal sphincter, the prostate, and the muscles of the penis. These contractions typically cause ejaculation -- they force stored semen to be expelled through the penis's urethral opening. The process takes from three to ten seconds, and is generally considered to be highly pleasurable
As a man ages, normally the amount of semen he ejaculates diminishes, and so does the duration of orgasms. This does not normally affect the pleasurable feeling, but merely shortens its duration.
After ejaculation, a refractory period usually occurs during which a man cannot achieve another orgasm. This can be anywhere from less than a minute to several hours, depending on age and other individual factors.
As a man nears orgasm during stimulation of the penis, he feels an intense and highly pleasurable pulsating sensation of neuromuscular euphoria. These pulses begin with a throb of the anal sphincter and travel to the tip of the penis. They eventually increase in speed and intensity as the orgasm approaches, until a final "plateau" of pleasure sustained for several seconds, the orgasm.
During orgasm, semen is 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 agree that it is highly pleasurable.

### In female humans
A human female orgasm lasts much longer than that of the male. It is preceded by erection of the clitoris and moistening of the vaginal opening. Some women exhibit a sex flush, a reddening of the skin over much of the body due to increased blood flow to the skin. As a woman nears orgasm, the clitoral glans moves inward under the clitoral hood, and the labia minora (inner lips) become darker. As orgasm becomes imminent, the outer third of the vagina tightens and narrows, while overall the vagina lengthens and dilates and also becomes congested from engorged soft tissue. The uterus then experiences muscular contractions. A woman experiences full orgasm when her uterus, vagina, anus, and pelvic muscles undergo a series of rhythmic contractions. Most women find these contractions very pleasurable. Recently, researchers from the University Medical Center of Groningen, the Netherlands, showed that it is possible to objectively recognize orgasms just by the specific frequencies of these contractions (abstract). After orgasm, the clitoris re-emerges from under the clitoral hood, and returns to its normal size, typically within ten minutes.

## 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 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.
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.

## 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. Marijuana enhances both male and female orgasms, while at the same time delaying ejaculation. GHB, GBL and 1,4 Butanediol are commonly used to enhance orgasms. Both male and female users of stimulants, such as 3,4-MDMA (ecstasy), and psychedelics like LSD and psilocybin-containing mushrooms sometimes report heightened sexual pleasure. Throughout history, recreational drugs have been used to enhance orgasm 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).

# In tantric sex
Tantric sex 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.
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).

# In other animals
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. Dolphin orgasms have also been witnessed during sexual intercourse with humans, a practice which some humans have indulged in with pleasure. 
See Animal sexuality.

# Books
- Gabriele Frobose, Rolf Frobose, Michael Gross (Translator): Lust and Love: Is it more than Chemistry? Publisher: Royal Society of Chemistry, ISBN 0-85404-867-7, (2006).
- Komisaruk, Barry R.; Beyer-Flores, Carlos; Whipple, Beverly. The Science of Orgasm. Baltimore, MD; London: The Johns Hopkins University Press, 2006 (hardcover, ISBN 0-8018-8490-X).

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