Elevation of the cervix and uterus Tenting , i. Physical or psychological stimulation, or both, leads to vasodilation and the increased blood flow engorges the three spongy areas that run along the length of the penis the two corpora cavernosa and the corpus spongiosum. The penis grows enlarged and firm, the skin of the scrotum is pulled tighter, and the testes are pulled up against the body.
After their mid-forties, some men report that they do not always have an erection when they are sexually aroused. Once erect, his penis may gain enough stimulation from contact with the inside of his clothing to maintain and encourage it for some time.
As the testicles continue to rise, a feeling of warmth may develop around them and the perineum. With further sexual stimulation, the heart rate increases, blood pressure rises and breathing becomes quicker.
Once this has started, it is likely that the man will continue to ejaculate and orgasm fully, with or without further stimulation. Equally, if sexual stimulation stops before orgasm, the physical effects of the stimulation, including the vasocongestion , will subside in a short time.
Repeated or prolonged stimulation without orgasm and ejaculation can lead to discomfort in the testes corresponding to the slang term " blue balls " . After orgasm and ejaculation, men usually experience a refractory period characterised by loss of erection, a subsidence in any sex flush, less interest in sex, and a feeling of relaxation that can be attributed to the neurohormones oxytocin and prolactin.
It can be as long as a few hours or days in mid-life and older men. Further changes to the internal organs also occur including to the internal shape of the vagina and to the position of the uterus within the pelvis. If sexual stimulation continues, then sexual arousal may peak into orgasm. After orgasm, some women do not want any further stimulation and the sexual arousal quickly dissipates.
Suggestions have been published for continuing the sexual excitement and moving from one orgasm into further stimulation and maintaining or regaining a state of sexual arousal that can lead to second and subsequent orgasms.
While young women may become sexually aroused quite easily, and reach orgasm relatively quickly with the right stimulation in the right circumstances, there are physiological and psychological changes to women's sexual arousal and responses as they age. Older women produce less vaginal lubrication and studies have investigated changes to degrees of satisfaction, frequency of sexual activity, to desire, sexual thoughts and fantasies , sexual arousal, beliefs about and attitudes to sex, pain, and the ability to reach orgasm in women in their 40s and after menopause.
Other factors have also been studied including socio-demographic variables, health, psychological variables, partner variables such as their partner's health or sexual problems, and lifestyle variables.
It appears that these other factors often have a greater impact on women's sexual functioning than their menopausal status. It is therefore seen as important always to understand the "context of women's lives" when studying their sexuality. In older women, decreased pelvic muscle tone may mean that it takes longer for arousal to lead to orgasm, may diminish the intensity of orgasms, and then cause more rapid resolution.
The uterus typically contracts during orgasm and, with advancing age, those contractions may actually become painful. Libido Psychological sexual arousal involves appraisal and evaluation of a stimulus, categorization of a stimulus as sexual, and an affective response. The cognitive aspects of sexual arousal in men are not completely known, but it does involve the appraisal and evaluation of the stimulus, categorization of the stimulus as sexual, and an affective response.
Specifically, while watching heterosexual erotic videos , men are more influenced by the sex of the actors portrayed in the stimulus, and men may be more likely than women to objectify the actors. This suggests the amygdala plays a critical role in the processing of sexually arousing visual stimuli in men. Psychological sexual arousal also has an effect on physiological mechanisms; Goldey and van Anders  showed that sexual cognitions impact hormone levels in women, such that sexual thoughts result in a rapid increase in testosterone in women who were not using hormonal contraception.
In terms of brain activation, researchers have suggested that amygdala responses are not solely determined by level of self-reported sexual arousal; Hamann and colleagues  found that women self-reported higher sexual arousal than men, but experienced lower levels of amygdala responses.
Models of human sexual response[ edit ] Human sexual response cycle[ edit ] Main article: Human sexual response cycle During the late s and early s, William H. Masters and Virginia E. Johnson conducted many important studies into human sexuality. In , they released Human Sexual Response, detailing four stages of physiological changes in humans during sexual stimulation: The first stage, aesthetic response, is an emotional reaction to noticing an attractive face or figure.
This emotional reaction produces an increase in attention toward the object of attraction, typically involving head and eye movements toward the attractive object. The second stage, approach response, progresses from the first and involves bodily movements towards the object. The final genital response stage recognizes that with both attention and closer proximity, physical reactions result in genital tumescence. Singer also stated that there is an array of other autonomic responses, but acknowledges that the research literature suggests that the genital response is the most reliable and convenient to measure in males.
The cycle results in an enhanced feeling of intimacy. Basson emphasizes the idea that a lack of spontaneous desire should not be taken as an indication of female sexual dysfunction ; many women experience sexual arousal and responsive desire simultaneously when they are engaged in sexual activity.
The basic incentive-motivation model of sex suggests that incentive cues in the environment invade the nervous system, which results in sexual motivation. Positive sexual experiences enhance motivation, while negative experiences reduce it.
Motivation and behaviour are organized hierarchically ; each are controlled by a combination direct external stimuli and indirect internal cognitions factors. Excitation and inhibition of behavior act at various levels of this hierarchical structure. For instance, an external stimulus may directly excite sexual arousal and motivation below a conscious level of awareness, while an internal cognition can elicit the same effects indirectly, through the conscious representation of a sexual image.
In the case of inhibition, sexual behavior can be active or conscious e. Toates emphasizes the importance considering cognitive representations in addition to external stimuli; he suggests that mental representations of incentives are interchangeable with excitatory external stimuli for eliciting sexual arousal and motivation.
They postulate that this variability depends on the interaction between an individual's sexual excitation system SES and sexual inhibition system SIS. These inhibition factors were interpreted as SIS1 inhibition due to the threat of performance failure and SIS2 inhibition due to the threat of performance consequences. A factor analysis of this questionnaire revealed only two factors: One lower order factor in the SESII-W labeled Arousal Contingency was particularly relevant; this factor explains the easy disruption of sexual arousal.
Regardless of the difference in these two questionnaires, both surveys' scores show normal distribution verifying the hypothesis that there is a normal individual variation in sexual arousal and inhibition.
On average, males score higher on sexual excitation and lower than females on both facets of sexual inhibition. As of yet, the differences in scores between genders have not been explained beyond the theoretical level.
The source of individual variability on the sexual excitation and inhibition systems is not known definitively. Even less is known about how these systems develop in individuals. Age of first masturbation has been used as a measure to assess sexual development. Age of masturbatory onset is much more variable in girls than boys, whose tend to be close to puberty. One twin-study has found evidence for the heritability of both factors of SIS, but research suggests that SES variability is down to environmental factors.
Assessment of genital arousal[ edit ] See also: Psychophysiology One way to study sexual arousal in women and men is to conduct sexual psychophysiological research in a laboratory setting. This field of research looks at physical sexual responses in addition to mental and emotional experiences of sexual arousal. Ivan Tarkhanov showed, in experiments on cutting and artificial emptying of the seminal vesicles , that the latter played the crucial role in the generation of sexual excitement in frogs.
Proceeding from these experimental results, Tarkhanov put forward a hypothesis that filling and evacuation of the seminal vesicles were the main biological cause which led to sexual arousal and its disappearance in mammals and humans. No generalisation has yet appeared, however. Unambiguous experimental evidence for the existence of the Tarkhanov regularity in human sexual behaviour has never been obtained.
If the level of this tension reaches threshold, sexual arousal occurs as the expression of necessity to let off steam. Kelly Clarkson University describes this model as follows: For centuries, the assumption was made that the longing for sexual interaction was innate, and an inner drive model was used to explain it.
It has been suggested that this model was much like a metaphor for a steam boiler. This view also assumed that there was some adverse physical consequence of not releasing the pressure. The instinct causes tensions within the central nervous system which spread out over the whole being; it is urgent and irresistible in nature and constantly repeats itself. An erection, for example, is pleasurable and painful at the same time. With an increase of sexual excitation, the tension increases and becomes wholly unpleasurable.
This condition becomes so unbearable that the individual is forced to seek release from these tensions and liberation from the painful feelings. The pain of tension which accompanies the increase in the intensity of the instinctual drives changes, with the discharge, into the pleasure of relaxation. Such an approach assumes sexual arousal to be a spontaneous desire that appears periodically like sensations of hunger and thirst. Drawing a parallel between these sensations and sexual excitation is widely accepted now: In this sense sex is a necessity of life, just as air, food, and warmth.
Sensations of hunger and thirst occur due to certain states of physiological insufficiency. The feeling of hunger results from the lack of glucose, fats and amino acids in blood. The feeling of thirst occurs in response to reduction of the water content of tissues. None of similar states of physiological deficiency responsible for the periodical appearance of sexual arousal has been revealed in human sexuality.
Penile plethysmograph and Thermography medical The most obvious response involved with sexual behaviour in males is penile erection. The use of the volume or circumference change during penile erection as a convenient measure of sexual arousal was first developed by Kurt Freund.
This is commonly measured using a strain gauge, a simple mercury strain gauge encompassed in a ring of rubber. The ring surrounds the penis , but does not constrict or cause discomfort. Studies have found temperature change specific to the genitals during sexual arousal, which supports the validity of this measure.
Vaginal photoplethysmograph Sexual arousal in women is characterized by vasocongestion of the genital tissues, including internal and external areas e. There are a variety of methods used to assess genital sexual arousal in women.
Vaginal photoplethysmography VPG can measure changes in vaginal blood volume or phasic changes in vasocongestion associated with each heartbeat. Clitoral photoplethysmography functions in a similar way to VPG, but measures changes in clitoral blood volume, rather than vaginal vasocongestion.
Thermography provides a direct measure of genital sexual arousal by measuring changes in temperature associated with increased blood flow to the external genital tissues.
Similarly, labial thermistor clips measure changes in temperature associated with genital engorgement; this method directly measures changes in temperature of the labia. More recently, laser doppler imaging LDI has been used as a direct measure of genital sexual arousal in women. LDI functions by measuring superficial changes in blood flow in the vulvar tissues. Category-specificity[ edit ] Category-specificity refers to a person showing sexual arousal to the categories of people they prefer to have sex with.
Sexual arousal studies involving category-specificity look at genital responses physiological changes , as well as subjective responses what people report their arousal levels to be.