Human sexual behavior

The human sexual response: excitement, plateau, orgasm, satiety.

Excitement can be measured in terms of physiologic measures that include genital vasocongestion (retention of fluids that results in enlargement of the sexual skin), but there are also psychological components that are not as easy to measure.

The plateau stage is the intemediate period between excitement and the culmination of the epidsode with orgasm

Orgasm is described by Kinsey as "the explosive discharge of muscular tensions at the peak of the sexual response... some if not most persons may become momentarily unconscious at the moment of orgasm"..."Sexual arousal and orgasm involvethe whole nervous system and, therefore, all parts of the body. Orgasm in the female matches the female in all regards except for the fact that it occurs without ejaculation" and that difference has been questioned by some investigators.

We generally believe that the sexual experience in other mammals is similar to man, but the lack of ability to demonstrate the presence of orgasm in other animals makes it impossible to study all aspects of sexual behavior in other animals. There are many aspects of the behavior that are similar across species, that are easily studied (particularly in males) like erection and ejaculation and refractory period (where human males also tend to have a longer refractory period than do women), but there has been considerable difficulty in studying orgasm in non-human animals. Do physiological responses = orgasm??

Hormonal Influences on Human Male Sexual Behavior

In many species - domestic species in particular- castration is used to decrease aggression and mating behavior. In humans, castration - or removal of the testes- has been used as punishment or as a consequence of triumph in war where the victors enslave a population and castrated the males. Nevertheless, the successfulness of castration to curb all aggressive behaviors or even sexual behavior is questionable.

Eunuchs (castrated men) were traditionally used as harem guards, and even Scheherezade talked about daliances with the eunuchs that was a way of life in the harem. Modern attempts to control behavior with castration have been similarly unsuccessful. In fact, it probably a good idea to reassess the work done with non-human animals in this regard. If one does, what you see is that even though castration is largely successful at reducing sexual behavior, the success rate is not 100%.

Depending on the extent of sexual experience, and on the strain of rat, 5-20% of rats do not stop copulating following castration.

Geldings (castrated male horses) have been reported to masturbate, as have fixed dogs and cats.

Thus, even though castration is 100% successful at preventing an individual from fertilizing a female, it does not prevent sexual activity in all males of most species that have been studied.

DEVELOPMENT AND AGING

Infant and prepubertal males can experience nocturnal erections indicating that erections are not dependent on homonal factors to insure potency. Similarly, prepubertal females have been observed to masturbate to apparent orgasm. Overt sexual behavior in children is infrequent. The role of prepubertal hormonal secetions on these behaviors is not well understood.

In males, with aging there is a decrease in testicular size and corresponding decrease in testosterone levels, with the most marked decreases occurring after the age of 60. Nevertheless, even men in their 80's have been reported to be sexually active and potent (as indicated by their ability to father children). Are there age related decreases in sexual behavior? Perhaps, but dissociating this effect from the decreased general activity and physical well being associated with aging is difficult to do.

-> In men as in other species correlations between absolute levels of testosterone and the degree of sexual behavior are very weak. The presence of the testosterone is, for most men, permissive - if it is required at all.

Do the studies with castration really prove that androgens are not required for sexual activity in males?

Remember that the adrenal gland also makes androgens - although these androgens are not as potent as testosterone. The prostate gland can make DHT. Fat (adipose tissue) further more, is a major depository for steroids and can even synthesize androgens, including DHT. Therefore, the residual sexual behavior seen in some males may reflect individual differences in alternative sources of andogens.

KALLMAN'S SYNDROME (hypogonadal)

lack of GnRH neurons (what would this cause to happen in an individual?)

-development during fetal stages: normal because mom makes GnRH and LH

- fail to develop male secondary sex characteristics unless treated.

Behavior: disinterest in sexual behavior, low levels of sexual activity, mild depression.

LH or testostosterone increase virilization. Report increased interest in sexual acts with hormone treatment, although behavior does not increase. WHY might this be the case?

Motivation vs performance

Are hypogonadal men less ABLE to respond with erections than normal men? No, strong erotic stimuli can stimulate an erection in these men - so they are not unable to have an erection. However, spontaneous erection occur infrwequently, increasing in frequency with hormone therapy.

DRUGS AND MALE SEXUAL BEHAVIOR

Alcohol: directly inhibits the ability to ejaculate

Chronic alcohol and Marijuana: gradual decline insexual ability. May result in damage to the nervous system and may inhibit steroid hormone production. May also result in infertility and impotence (especially true for alcohol).

Barbiturate, opiates (heroin, morphine), antianxiety drugs (valium), antidepressants (prozac), antihypertensives and anticonvulsants usually reduce male sexual behvior. This of course is in spite of the widespread anecdotal - based belief that these drugs may enhance sexual ability.

Conversely, acute use of stimulants such as amphetamine and cocaine may temporarily stimulate some components of male sexual behavior. Chronic use of these dugs, however, results insexual dysfunction. Addicted individuals also tend to become disinterested in sexual behavior (and more interested in obtaining drugs).

Anabolic steroids - these drugs are synthetic forms of testosterone - whaat do you think they do?

Women and Sexual Behavior

Desire varies with the menstrual cycle, but ability does not.

Estrogen- may enhance sexual motivation and by increasing vaginal lubrication sexual ability indirectly.

Progesterone - the most consistent effect of progesterone on female sexual behavior is to inhibit sexual activity. Is this because progesterone decreases female attractiveness? Or does it inhibit sexual motivation? Reports from women taking progesterone-based contraceptives ae difficult to interpret.

Androgens - there has been a suggestion that androgens in women are the primary hormone inducing sexual motivation, however, since androgens that are administered to women can be converted to estrogen - the results of most studies are difficult to interpret.

Oxytocin - This hormone has been studied recently for its role in sexual and affiliative behaviors for a number of reasons. First, it is released during orgasm in both men and women. It is also produced and released during ejaculation by the prostate in men. Physical stimulation can induce oxytocin release in women. It is associated both with sexual satiety and with the formation of social bonds. Species that form monogamous pairs tend to have a higher release of oxytocin during sexual behavior and more widespread occurrance of oxytocin receptors in the brain. However, oxytocin is also associated with sexual satiety, so some hypothesize that oxytocin induces the refractory state following orgasm.