Fun fact: an Orgasm can raise a person's pain threshold to as much as twice its usual capacity.
Sofie Roos, a licensed sexologist, relationship therapist and author at Passionerad, walked HuffPost UK through what happens during orgasm inside the body and brain. She describes a "cocktail of feel-good hormones" released in "a very short period of time."
"The brain's reward system [gets activated], and chemicals produced by our body, such as dopamine and oxytocin, [are] released into the bloodstream," Roos said.
Oxytocin, Roos said, makes us feel relaxed and close to a partner.
The same essay, by Barry R. Komisaruk, Carlos Beyer and Beverly Whipple, says serotonin works more like a brake: antidepressants that raise serotonin levels tend to produce anorgasmia, the inability to orgasm. How neurons produce the pleasurable feeling itself is still open. "We do not know," the authors write.
Roos said the body's natural pain-relief system is also activated during climax. HuffPost reports that the paraventricular nucleus has been shown to release oxytocin, which can help relieve pain, during both childbirth and vaginal sex. The Psychologist essay cites a 1985 study by Whipple and Komisaruk showing that pain thresholds in women more than doubled during orgasm.
Roos said to expect a "higher pulse, higher blood pressure and more intense breathing" when aroused. HuffPost reports that blood pressure doesn't seem to peak at orgasm, but heart rate does, and both get back to normal about 10 minutes afterward.
Orgasm leads to "rhythmic contractions in the muscles around our genitals," Roos said. HuffPost says these are usually just under a second apart and last for several seconds. It adds that women who have more orgasms seem to have stronger pelvic floor muscles and lower odds of urinary incontinence.
Detailed brain scans show the brain becoming far more active during orgasm, not less, despite earlier beliefs.
Afterward, Roos said, people can "feel sleepy, relaxed, and dozy." HuffPost says that may come from the physical exertion of sex, the release of chemicals like prolactin, vasopressin and oxytocin, or both. It also reports that orgasms from partnered sex seem to lead to up to four times as much prolactin as those from masturbation, for reasons researchers don't yet understand.
"I'd also like to point out that all people's orgasms are very individual... what happens in your body and how you're feeling afterward is different to everyone, and can also shift from time to time," Roos said.