What are the chemicals involved in physical attraction? How do they effect the nervous system and emotions?

Answer 1

Below are references (1,2) to quite extensive and recent reviews on the subject (the first and more recent one isn't in open access, alas).

The bottomline is that for humans, research on pheromones' effect on behaviour is still in its quite early days and much of the evidence is extended from animals and/or speculative. But it becomes apparent that the effect of pheromones on human behavior seems to be relatively subtle (compared to insects, for example) and it seems unlikely that external use of pheromones can drive anyone completely 'head over heels'.

BEHAVIOR

Two placebo-controlled studies on pheromones' effect on human behavior 'in natural environment' have been carried out so far. One of them involved males applying pheromones with their aftershave lotion for 2 weeks (3) and the other one featured females applying pheromones for 2 weeks with their perfume (4). Pheromone-applying males reported a significant increase in ‘sexual intercourse’ and ‘sleeping next to a romantic partner’ as compared to the group that had placebo in their aftershave instead. As for females, an increase in ‘sexual intercourse’ and ‘formal dating' was reported. However, the authors of the review (1) argue that these studies did not properly control for attractiveness and social status of pheromone v. placebo-applying groups. If so, the researchers might even have "subconsciously" allocated more sexually attractive subjects to the 'pheromone' group.

However, these relatively unconvincing results might also mean that people already excrete 'saturating' concentrations of pheromones and this is why external application of additional amounts does not make much difference. This seems to be more or less likely, as humans are clearly attracted to the smell of the opposite sex and smell definitely plays a role in sexual rituals, such as oral sex and perhaps even kissing.

BIOCHEMISTRY

Animals sense pheromones by a special region in their noses called vomeronasal organ (5). In humans, this organ regresses during embryonic development. However, recent research suggests that it is still active in adults. It is more or less clear that pheromones (and olfactory information in general) do play a role in human sexual behaviour. At the neurochemical level, pheromones activate the secretion of gonadotropin releasing hormone (GnRH) from the hypotalamus. At least one of the effects of GnRH is that it triggers the secretion of gonadotropins from the pituitary gland, which, in turn, promote follicle maturation in the ovaries in females, testosterone and sperm production in males.

Answer 2

They are called pheromones. There is too much to tell you on here. It would probably take 3-4 days to include everything. Enter pheromones in to a search engine like google.

Answer 3

Pheromones. More info at link below.

Aloha

Answer 4

Musk