By Professor BB
[Professor BB has worked in the field of sexuality research and education for the past 8 years. She has numerous publications and been invited to speak at professional meetings across the U.S. and in Europe. Professor BB is a popular lecturer of sexuality and human anatomy and physiology in her home state of New Jersey.]
Having an orgasm is no doubt one of the most pleasurable sensations known to humankind. For many individuals the ultimate goal of a sexual experience, whether it be alone or with a partner, is to have an orgasm. Although orgasms are a paramount part of many sexual experiences, relativity little is known about the underlying physiological mechanisms that control orgasmic responses.
The word "orgasm" is derived from the Greek word orgasmos, which means "to swell" or "to be lustful." There is no one universally accepted definition for orgasm, and we don't know why humans evolved the capability to have orgasms. In both males and females, an orgasm brings about numerous physiological and neurochemical changes in the body. The intense feelings of pleasure associated with orgasm are the result of the release of built-up neuromuscular tension known as myotonia.
by both males and females are very similar.
Based on direct laboratory observation of more than 10,000 episodes of sexual activity in over 600 men and women, two sexuality-research pioneers, William Masters and Virginia Johnson, concluded that the human sexual response cycle consists of four distinct stages. These four stages are excitement, plateau, orgasm, and resolution. The orgasmic stage is the shortest but most intense of the four. There are striking similarities in the physiological events that occur in both the male and female body during orgasm. Studies have also shown that during orgasm the feelings experienced by both males and females are very similar. One study showed that even "sex experts" could not even reliably distinguish between written accounts of male and female orgasms.
Sexual responses may be either psychogenic or reflexogenic in nature. When erection occurs as the result of direct physical stimulation, it is known as a reflexogenic erection. When an erection results from erotic thoughts or viewing erotic material, it is known as a psychogenic erection. Sexual arousal in the female may also be either psychogenic or reflexogenic in nature and is typically associated with an increase in vaginal lubrication.
In the male, direct genital stimulation usually causes an erection within a few seconds. An erection is the result of an increase in blood flow to the penile blood vessels and tissue. In addition to erection, the excitement stage in the male is characterized by the testicles being pulled closer to the body and a tensing and thickening of the skin of the scrotum. The muscles of the body also begin to tense up, and the heart rate, breathing rate, and blood pressure begin to increase. Some males may also experience nipple erection and a reddening of the skin of their face, chest, and neck during the excitement phase. The reddening of the skin, which is similar in appearance to a measles rash, is known as a sex flush and is usually more predominate in females.
In the female, the excitement stage of sexual arousal is characterized by the onset of vaginal lubrication, clitoral erection, changes in the size and shape of the labia, nipple erection, and swelling of the breasts. Women also experience the buildup of muscle tension and an increase in the heart rate, breathing rate, and blood pressure.
In both the male and female, the plateau stage is associated with further increases in muscle tension, heart rate, breathing rate, and blood pressure, as well as an increase in the intensity of the sex flush. In the male, the glans (head) of the penis turns a deeper red or purplish color, and a few drops of slippery fluid (often referred to as "pre-cum" or "love drops") may be released from the urethra. In the female during the plateau phase the labia appear darker in color, the clitoris retracts, and small glands outside the vaginal opening secrete a mucus-like fluid.
For the male, orgasm almost always includes ejaculation, which occurs in two distinct stages: emission and expulsion. Emission occurs when semen collects in an upper part of the urethra known as the urethral bulb. As more semen collects in the urethral bulb, he develops the feeling he is about to ejaculate. This feeling is known as ejaculatory inevitability and usually lasts for 2 to 3 seconds. This is the "point of no return" – the man cannot be stopped from having the orgasm at this point. Expulsion, the second stage, involves rhythmic contractions of the muscles around the base of the penis and anus. These muscular contractions cause the semen to be propelled down the urethra and out of the body. There are normally 4 to 5 rhythmic contractions that occur at 0.8-second intervals, with the first ones being the strongest and most intense. During orgasm in both males and females the heart rate, blood pressure, and breathing rate all reach peak levels. Both males and females also release a hormone known as oxytocin from their posterior pituitary glands. This hormone is believed to help strengthen the pelvic-muscle contractions associated with orgasm.
The average male ejaculates 3 to 5 ml of semen at a time. Semen contains sperm as well as secretions produced by the seminal vesicles, prostate gland, and Cowper's glands. In a healthy fertile male, each one ml of ejaculate contains an average of 50 to 100 million sperm. Although this may seem like a very large number, sperm actually account for only 5% of the overall ejaculate volume. As a male ages or if he ejaculates repeatedly with only a short duration between ejaculations, the semen volume may be reduced. A "dry" orgasm occurs when there is no ejaculation. These "dry" orgasms are common in prepubescent boys and can also occur in some men who have prostate disease, certain neurological impairments, or spinal cord injuries.
Orgasm in women involves rhythmic contractions of the uterus and the muscles that surround the vagina. Women normally experience 3 to 10 very strong contractions that occur at 0.8-second intervals. These initial contractions may be followed by 3 to 6 slower and weaker contractions. Some women also release a small gush of fluid. Many women find it necessary to have direct stimulation of the clitoris in order to have an orgasm. For this reason, many women can reach orgasm much easier and faster through masturbation than through intercourse.
Orgasm intensity and its associated feelings can both vary greatly. Sometimes a person experiences an orgasm that makes them feel like their entire body is going to explode, while at other times they might just experience a pleasant feeling of muscle relaxation. Influencing factors include a persons mood, psychological state, level of desire, relation to partner, drug or alcohol use, expectations, physical condition, and time since the last orgasm.
After orgasm in the male, there is usually a complete loss of the erection within a few minutes. During this resolution stage the entire body returns to an unaroused state. Most men experience a refractory period, during which no type of stimulation is able to bring about another erection. The length of the refractory period can vary dramatically between men; age, mood, drug use, and stimulation type can all be factors. The typical refractory period for a male in his teens or 20s is just a few minutes, whereas in the older male it may be a few hours or even a day.
Women do not display a refractory period and are therefore capable of experiencing multiple orgasms. However, a recent laboratory study did document a case of a male who was able to have multiple ejaculatory orgasms without any refractory period between them.