"Sex is a part of nature. I go along with nature.” - Marilyn Monroe

(pls make sure you read this carefully)

Sex can be a pretty mysterious experience — and just as your question implies, there are a lot of physiological and psychological components at play that may result in what can be very pleasurable outcomes. So why exactly does sex, sexual touch, sexual thoughts, orgasm, and other sexy exchanges trigger good feelings? Let’s take a closer look.
Sexual arousal and orgasm are largely a result of environmental and psychological stimuli (anything that you see or think about that turns you on!) coupled with neurochemical mechanisms (the response your brain has to erotic imagery, thoughts, or other types of stimulation). Neurotransmitters (responsible for sending signals from your brain cells to other areas of the body) and hormones present during sexual excitement, orgasm, and post-orgasm can tell us a lot about the biological mechanisms of sex and pleasure. Here are a few key players:

Dopamine — Correlated with increased sexual arousal and interest, this neurotransmitter has been found to be secreted during sexual excitement. Dopamine agonists (drugs that act like dopamine when ingested) have been used to treat sexual dysfunction.

Prolactin — This hormone is known to surge immediately following orgasm. This may explain the refractory period, when it is sometimes more difficult to immediately orgasm a second or third time, and may also be related to a feeling of “coming down” or sexual satiety after climax. Studies on rats with chronically elevated levels of prolactin (also known as
hyperprolactinemia , a condition that can also occur in humans) have been linked with decreased sexual interest, sexual arousal, and sexual response.

Oxytocin — Sometimes referred to as the “bonding hormone”, oxytocin is believed to contribute to feelings of intimacy, closeness, and trust, and is released in combination with prolactin post orgasm.

Serotonin — A neurotransmitter present during sexual arousal that is understood to contribute to feelings of happiness and well-being.

Norepinephrine — This neurotransmitter acts to constrict or dilate blood vessels in the genitals and other areas of the body during sexual stimulation, making these areas more sensitive to touch.

The combination and flow of these hormones and neurotransmitters during the sexual response cycle can help contextualize why sexual stimulation from any number of visual, physical, or other sources elicit a multitude of positive feelings. In addition, studies of the brain during orgasm show surprisingly little activity, perhaps suggesting that during climax, you can be in a somewhat transcendent state, allowing pleasure to override any worries or commotion from daily life.

From a very primitive, reproductive perspective, the pleasure of sex is certainly helpful with species survival! But mating for offspring definitely is not the only reason people enjoy sex. Sexual pleasure and exploration can lend itself to bonding with others, self-expression, stress reduction, and a wide variety of other enjoyable outcomes.

We certainly don’t know all there is to understands about sexual pleasure — and everyone’s sexual experiences vary in unique ways.