8 Things That Happen To Your Body During Sex

The racing heart, the flushed skin, the complete calm (or the urge to nap, immediately) in the afterglow. Sex changes a person… at least for a few minutes. And not just because you're caught in the throes of passion, but because the whole process—from the inklings of desire to an orgasmic climax and beyond—is full of physiological reactions from your head to your toes (well, at least through your thighs). (If an orgasmic climax seems as likely as your laundry doing itself, this 4 in 1 pressure sensitive massager from Rodale's is here for you.)

Knowing these inner workings of your sex life may not seem like it matters much if you're happy with your habits between the sheets. But when something's off, that knowledge might help you pinpoint the problem. "There are so many organs and systems involved in sexual function, and you need every single one to be in working order for everything to go well," says Lauren Streicher, MD, clinical associate professor of obstetrics and gynecology at the Feinberg School of Medicine and author of Sex Rx. "It's not just all about hormones." Here's what else is going on while you're getting it on.

Brain chemicals and hormones get busy.

"Libido starts in the brain," Streicher says. What you might call "being in the mood," scientists might call the right balance of neurotransmitters, like serotonin and dopamine, to facilitate desire. While the brain doesn't produce estrogen or testosterone, receptors for those crucial hormones are activated in the brain, Streicher says. "Women's excitement phase is above the shoulders, versus below the waist for men," says ob-gyn Sherry A. Ross, MD, author of She-ology: The Definitive Guide to Women’s Intimate Health. Period. Which is why racing thoughts, depression, stress, or even just thinking about your to-do list are pretty instant mood-killers.

As sexual excitement builds, adrenaline starts pumping, as do all three sex hormones, Ross says. That's right, it's not only estrogen that accounts for your sex drive (if it were, Streicher adds, menopausal women would be in trouble) but testosterone and progesterone, too.

During and after sex, endorphins surge, leading to feelings of euphoria, deep relaxation, and sometimes even less pain, says Johannes Hinrich von Borstel, author of Heart: The inside Story of Our Body’s More Heroic Organ. Plus, there’s that famed oxytocin, the so-called "cuddle hormone," triggered by all that affectionate physical contact, von Borstel says, which leads to feelings of lovingness, lower blood pressure, and less stress

Your heart flutters.

You're excited, you're physically active, and you need blood to get to the areas of main attraction, so your heartbeat picks up to pump blood around the body, with a specific focus on the genitals. Your breathing rate will increase too, to help your heart maintain this quickened pace, Ross says. (Try these 5 best sex positions to help you orgasm.) In this way, sex is almost like a workout, von Borstel says, "and it's much more fun than struggling outside on a bicycle or running in the rain."

Blood vessels dilate.

As your heart rate picks up, your blood vessels dilate or expand, which allows more blood to flow to those erogenous zones. "More blood flow to the genitals is why a guy gets an erection and a woman starts to lubricate," Streicher explains.

Skin flushes.

Dilated blood vessels also mean more blood gets to the skin, too. That's what behind any flushing, blushing, or warmth to the skin.

Muscles contract.

Especially those in the pelvic floor, and nearby ab and leg muscles, Ross says, in preparation for climax. "Your body tenses up before the relaxation of an orgasm," she says. (These 6 exercises will strengthen your pelvic floor and help you orgasm.)

The vagina lubricates.

Blood flow down below stimulates not just lubrication in the vagina, but swelling of the labia and clitoris, Ross says. This effect can be amplified with direct physical stimulation to the area, she says.