What contributes to sexual desire?
It is noted that, scientifically, its pretty hard to adequately define sexual arousal, although it can be looked at through both an objective portion (empirical changes in body heat, breathing rates, increased sensitivity of the genitalia) and subjective portion (self-report) whereas orgasm is defined a bit more accurately as a transient, intense, peak of pleasure and euphoria and altered state of consciousness, usually paired with an induction of well-being and contentment.
Although context is important for female arousal there are also neurotransmitters and hormones that mediate or are responsive to this process. Like men, female arousal seems to be mediated by hypothalamic dopamine and androgens like testostereone, insofar that a case study has noted lack of sexual desire in a woman suffering from a deficiency of a certain androgen.
Externally, the scent of the desired gender appears to influence libido as smelling androgens seems to stimulate heterosexual females and smelling estrogens seems to stimulate both heterosexual men and lesbians, even going as far to increase testosterone in men. That being said, the study of human pheromones is young and needs more research.
What happens in my body when I orgasm?
Various brain regions are important for female arousal and orgasm.
Can I take anything to enhance orgasm?
At the moment, no compound has a large body of evidence behind it suggesting enhancement of female orgasm; merely promising routes that await more research. Most research to this date has been in preventing a decline in sexual desire that is induced by anti-depressant medication, the results of which may not apply to healthy women.
Frequent orgasms are highly correlated with an increased quality of life, yet this correlation is positive for sex and negative for non-sexual forms of orgasm and anal. Although not necessarily causative, numerous studies have found similar results.
Sex appears to be good for health, not necessarily orgasm.
There have been differences noted between primate and non-primate sexual control, so it is questionable as to whether mice and rats (rodent models) are an accurate model for humans in this regard.
Additionally, one of the main research techniques to induce sexual arousal (showing pictures and videos of the sex(s) that the subject reports to enjoy) seems to be more effective in males relative to females. Context appears to be important as well, with videos labelled 'erotic' eliciting more excitement than videos labelled 'documentaries'.