Human Sexuality

Body Area Excitement Phase Orgasm Phase Resolution Phase 

Penis Vasocongestion, penile erection Ejaculation Detumescence 

Scrotum Tightening and lifting No change Decrease to baseline size 

Breasts Nipple erection No change Return to baseline 

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It is known that the brain is one of the most sensitive sites of action of steroids in utero, and recently there have been suggestions that EDs may affect normal brain development and behaviour. For example, it has been alleged that in utero exposure to polychlorinated biphenyl compounds (PCBs) resulted in adverse effects on neurologic and intellectual function (memory and attention) in young children born to women who had eaten PCB contaminated fish in the USA." It has also been speculated that exposure to environmental pollutants with steroidal activity may be infinencing human sexual development and sexually controlled behavioiir." ... 

Testosterone, the principal male sex steroid hormone, is synthesized in five steps from cholesterol, as shown below. In the last step, five isozymes catalyze the 17/3-hydroxysteroid dehydrogenase reactions that interconvert 4-androstenedione and testosterone. Defects in the synthesis or action of testosterone can impair the development of the male phenotype during embryogenesis and cause the disorders of human sexuality termed male pseudohermaphroditism. Specifically, mutations in isozyme 3 of the 17/3-hydroxysteroid dehydrogenase in the fetal testis impair the for-... 

Boyer EW, Quang L, Woolf A, et al Use of physostigmine in the management of gamma-hydroxybutyrate overdose (letter). Ann Emerg Med 38 346, 2001 Buffiim J, Moser C MDMA and human sexual dysfunction. J Psychoactive Drugs 18 355-359, 1986... 

Metabolic differences betw een humans and other animals may account for some of the interspecies differences in specific organ toxicity of trichloroethylene (see below). Among humans, sexual differences due mainly to the effects of body fat content on trichloroethylene absorption are expected based on PBPK modeling (see Section 2.3.5). 

Benton, D. and Wasted, V. (1986) Effects of androstenol on human sexual arousal. Biol. Psychol. 22, 141-147. 

Rahman, Q. and Wilson, G.D. (2003a) Bom gay The psychobiology of human sexual orientation. Pers. Indiv. Differ. 34, 1337-1382. 

Following Smith (1984) I have argued that the risk of sperm warfare has helped to shape the evolution of just about every aspect of human sexuality - from testis size to penis shape, and from the wet sheet phenomenon to masturbation and the female orgasm (Baker and Beilis 1995 Baker 1996). 

The main theme of this rather multi-faceted paper is that the importance of sperm competition to human sexuality varies not only from person to person but also from one stage of sexual ontogeny to another. 

A major feature of human sexual ontogeny is that a man eventually settles into a (relatively) long-term relationship with a woman, most often as a prelude to reproduction. 

As Sperm Competition Theory is applied to more and more organisms, its early promise as a paradigm for the understanding of sexual behaviour has been maintained. I suggest that human sexuality is no exception. As I hope this paper continues to show, there are few aspects of human copulation, masturbation and infidelity that have not been shaped during evolution, at least in part, by the threat of sperm competition. 

Gangestad, S. W. and Thornhill, R. (In Press). Human sexual selection and developmental stability. In Evolutionary Social Psychology (ed. J. A. Simpson and D. T. Kenrick). Hillsdale, New Jersey Lawrence Erlbaum. 

Thornhill, R. and Gangestad, S. W. (1994). Fluctuating asymmetry and human sexual behaviour. Psychological Science 5, 297-302. 

Human sexual function and fertility disorders include, e.g., spontaneous abortions, impaired spermatogenesis, menstrual disorders, impotence, and early menopause. 

Beach FA (1979) Animal models for human sexuality. In Sex, hormones, and behavior. London, Elsevier/North-Holland, pp 113-143 (Ciba Foundation Symposium No. 62). 

From a simple psychopharmacological perspective, the human sexual response can be divided into three phases, each with distinct and relatively nonoverlapping neurotransmitter functions, namely, libido, arousal, and orgasm. 

FIGURE 14—2. Psychopharmacology of the human sexual response, part 2. Sexual arousal in peripheral genitalia is accompanied by erections in men and lubrication and swelling in women. Both nitric oxide and acetylcholine mediate these actions. 

In summary, there are three major psychopharmacological stages of the human sexual response (Fig. 14—7). Multiple neurotransmitters mediate these stages, but only some of them are understood. Libido (stage 1) has dopaminergic dimensions to its pharmacology. The mechanism of arousal (stage 2), which is characterized by... 

FIGURE 14—6. Psychopharmacology of the human sexual response, part 3. Orgasm is the third stage of the human sexual response, accompanied by ejaculation in men. Serotonin exerts an inhibitory action on orgasm and norepinephrine an excitatory or facilitatory action. 

FIGURE 14-30. Psychopharmacology is beginning to identify new therapies that are sex-specific and related to sexual functioning. These include treatments for the human sexual response, especially for erectile dysfunction in men, as well as a better appreciation of the role of hormones in managing mood and cognitive disorders in women. 

In this chapter, issues in psychopharmacology related to sex and sexuality were discussed. This included an overview of the neurotransmitter mechanisms involved in the three psychopharmacological stages of the human sexual response, namely libido, arousal, and orgasm. Neurotransmitters that mediate each of these three stages were discussed, as well as drugs that facilitate and inhibit these stages. A specific introduction to the nitric oxide neurotransmitter system was outlined. 

To explore the psychopharmacology of the human sexual response, including libido, arousal and orgasm. 

My general knowledge about the role of neurotransmitters in the human sexual response was enhanced. ... 

Masters, W.H., and V.E. Johnson. 1966. Human sexual response. Boston Little, Brown. 

Sensuality and Sexuality. MDMA, often called a "hug drug," has a deserved reputation in this arena. It increases intimacy, but in most instances tends to reduce genital sexuality. The standard finding about this substance was expressed by John Buffum and Charles Moser in the October 1985 Journal of Psychoactive Drugs when they reported on the first survey of MDMA s effects on human sexuality. "It appears that MDMA does not increase sexual excitation or sexual desire in a majority of individuals," they wrote,... 

Masters, W. Johnson, V. Human Sexual Response Little Brown, and Co. Boston, 1966, Ch. 6. 

For the last 500 years Shakespeare probably has been the author most frequently cited on the acute effects of alcohol on human sexual response. The specific reference is from Macbeth, Act 2, Scene 2 It [alcohol] provokes and unprovokes it provokes the desire, but it takes away from the performance. It turns out that the results of experimental studies are in part consistent with Shakespeare s observations. 

Efforts have been made to systematically study human sexual response to a dose of alcohol, but only in the past 30 years or so has it been possible to do well-controlled research on this topic. The significant breakthroughs have been the invention of the penile strain gauge to measure penile erectile response and the photoplethysmograph to measure vaginal blood volume and pressure. These advances paved the way for experimental study of human. sexual response and alcohol. 

Hyde, J. S., 8c DeLsimater, J. O. (2006). Understanding human sexuality (9th cd.). New York McGraw-Hill. 

Kohl, J.V., Francoeur, R.T. 1995. The Scent of Eros Mysteries of Odour in Human Sexuality, Continuum, New York. 

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