The phases of human sexual response are sexual desire, arousal (excitement), orgasm and resolution (Table Female sexual response cycle).

Table Female sexual response cycle

Parameter Excitement phase Orgasm ic phase Resolution phase
Time interval Several minutes to several hours 3-25 s 10-15 min if orgasm; if no orgasm 0.5 h to 1 day
Skin Inconsistent sexual flush: maculopapular rash may appear on abdomen, anterior chest, neck, face Well-developed flush Flush disappears. Inconsistent perspiration on palms and soles
Breasts Nipple erection in two-thirds of women; areola enlargement. Breast size increases by 25% Breasts may become tremulous Return to normal size within an hour
Clitoris Enlargement in diameter of glans and shaft No changes Detumescence in 5-30 min; if no orgasm, several hours
Labia majora Congestion and edema. Eversion No change Return to normal size in 1-15 min
Labia minora Congestion, size increases 2-3 times. Eversion. Color change to deep red Contraction of proximal labia minora Return to normal within 5 min
Bartholin’s glands Secretion
Vagina Color: dark purple. Lubrication, ballooning of upper third, constriction of lower third prior to orgasm. 3-15 contractions of the lower third Congestion disappears in seconds. If no orgasm, in 20-30 min
Uterus Elevation in the pelvis Contractions throughout orgasm Return to normal position
Rectum Rhythmic contractions of anal sphincter
Others Myotonia Loss of voluntary muscle control Return to baseline

Desire

This phase is characterized by sexual fantasies and the desire to have sexual activity. It is distinct from other phases because it is psychological and reflects motivations, drives and personality.

Arousal (excitement)

The physiologic purpose of sexual arousal is two-fold: (1) to facilitate the painless penetration of the vagina by the penis and to reduce the risk of discomfort and trauma during sexual intercourse; and (2) to induce a pleasure response which will motivate an individual to seek sexual activity on another occasion. Sexual arousal is dependent on sexual stimuli, of which there are two types: those dependent on the brain (psychic), such as sight (visual), sound (auditory), smell (olfactory) and sexual fantasies, and those dependent on touch (reflexive). The latter can be effective independent of the brain, e.g., following spinal cord transection. The most powerful of these stimuli is touch, especially of the erogenous areas of the body. There is a wide variability between persons and within the same person in sensitivity to sexual stimuli, which may be under biochemical, hormonal, circadian or social influence.

Sexual stimulation leads to central and peripheral arousal and genital response. Central arousal is the state of alertness that focuses the attention on sexual stimulation. Peripheral arousal is increased sensitivity to touch. In the female, genital responses include local vasocongestion, vaginal lubrication, clitoral erection, uterine elevation and increased muscle tone. Local vasocongestion leads to eversion of labia majora and minora, thereby facilitating penile penetration. As a result of increased tone of the pubococcygeal muscle, the lower third of the vagina ‘narrows’ and the upper third widens and elongates. The uterus occupies a higher position in the pelvis and the moisture of the secretions facilitates penile entry and thrusting. The neural pathways controlling these changes are via the parasympathetic sacral outflow of S2-S4 via the nervi erigentes. In addition, there is involvement in the sympathetic nervous system leading to increased alertness, rise of pulse and blood pressure.

Orgasm and resolution

It is difficult to define orgasm but two such attempts described it as an ‘explosive discharge of neuromuscular tension’ or simply as ‘piercing sexual pleasure’. In the female, a few seconds after the start of orgasm, there is a spasm of the muscles surrounding the lower third of the vagina, known as the orgasmic platform, followed by between five and eight rhythmic contractions. In some women, anal and uterine contractions are also observed. Orgasm is a sympathetic reflex, and during orgasm there is a rise in pulse rate (up to 160 beats per minute), blood pressure (both systolic and diastolic: by 20-40 mmHg), respiration rate and pupillary dilation. Orgasm lasts between 3 and 25 s and may be associated with a slight clouding of consciousness. After the orgasm, a period of calm follows which is termed resolution. Various surveys suggest that 30-50% of women experience orgasm from coitus, a larger number from clitoral stimulation, and 10-20% do not experience orgasm in spite of being highly aroused sexually. It appears that orgasm in women is not a purely reflexive event as in men but is more of a learned ability. The number of women able to experience orgasm increases with age. In adolescence only 50% of women experience orgasm; this increases to 95% by age 35. In women, the refractory period is not very well defined and some even question its existence. Kinsey reports that 14% of women are capable of experiencing multiple orgasms. The time course of sexual responses in the female is longer than in the male. A summary of the body changes during the sexual response cycle is provided in Table Female sexual response cycle.

The sexual response is a unique blend of psychologic and physiologic experiences. Psychosexual development, attitudes toward sexuality and the sexual partner are directly involved with, and affect, the nature of human sexual response (Table Some factors affecting sexual response).

Table Some factors affecting sexual response

Stress
Age
Relationship with partner
Physical and mental health
Sexual knowledge/education
Self-image and confidence
Sexual experiences
Sexual attitudes/values
Parental influence/attitude
Sexual novelty/boredom
Drug/alcohol addiction

Stress is a pervasive cause of sexual problems. Difficulties at work, unemployment, money concerns, worries over children and interpersonal conflicts all contribute to sexual problems. The presence of relationship problems is one of the most damaging types of stress as the source of the stress and the sexual partner are the same person. An example of relationship problems is excessive politeness and consideration, presenting with a low level of sexual activity, vaginismus or impotence. Another example is when the couple has different sexual attitudes or different sexual desires. In some couples, there is a protective realtionship problem. It happens when one of the partners who does not enjoy sex at the best of times is protecting the sicker partner from the stresses of sex on spurious medical grounds. We should not forget extramarital affairs, which may lead to a lack of desire in the partner who feels betrayed.

Most psychiatric conditions can lead to sexual problems. It is amply documented that depression leads to decreased motivation and sex drive. In anxiety states sexual problems are common. In schizophrenia the libido may be preserved, but interpersonal relationship problems inhibit sexual activity.

Poor general health, notably peripheral vascular disease and diabetes, through decreased vascular response and sensitivity, may lead to an insufficient sexual response. For some, the rigor of sex may be too much a demand for the rest of the body, even if there is a desire and genital response.

Excess alcohol may cause (1) low levels of testosterone; (2) neuropathy and decreased genital sensitivity; (3) hypertension; (4) depression; and (5) jealousy and partnership problems. In addition, the intoxicated partner may be clumsy, smelly or demanding. In drug addiction, the sphere of interest can be so narrow as to exclude everything else but drugs. Aversion to sex is well documented in people who have experienced sexual abuse in childhood or rape.

An excessively rigid and cold upbringing can be particularly destructive for a person’s sex life. On the one hand, it may lead to promiscuity, where the person seeks substitutes for love and affection and reassurance; on the other hand, it may lead to decreased desire and arousal and the view that sex is dirty.

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