What happens to your body and brain during sex

Dopamine is released, oxytocin goes wild, and a whole lot more

Text: Jo

couple kissing in dimly lit room before intercourse, black and white

We see sex everywhere: from fashion to food, social media to Singapore Zoo. But while we all know what intercourse looks like from the outside (realistic or not!), what’s taking place with the chemicals inside our bodies and brains is a bit harder to grasp. “Huge changes occur both physically and mentally during sex,” explains Maria Ludeke, Director, Counsellor, Psychotherapist & Executive Coach at Aspire Counselling. “Basically, your brain and body go through a myriad of different chemical reactions, such as the release of dopamine and oxytocin, which are all triggered by your individual sex response cycle.”

The first sexual response cycle was a four-stage model of desire originally created in 1966 and referred to the sexual phases of excitement, plateau, orgasm and resolution. The most recent sexual response cycle, however, is the Nonlinear Model of Sexual Response by Rosemary Bassem, which is a more fluid reaction-response-reaction cycle, particularly for women who can orgasm, then experience arousal and orgasm again in one sexual experience (go girls!).

“While men and women experience the same four sex cycle stages, they’re not necessarily linear, nor do they experience them in the same way at the same time,” explains Maria. “Everyone’s body is different, so as long is the sex is enjoyable and consensual for both parties, anything within the sex response spectrum is considered ‘normal’.”

What is consistent is that, no matter where you are on the sexual response cycle, you'll be reaping the health benefits of your body’s chemical balance — and understanding this has the potential to make sex amazing.

Here’s what else you need to know.

Sexual response phase 1: Desire

There are situations where just thinking about intercourse can prime your body for it, and if that’s you, welcome to the first stage of your sex response cycle (so be careful where your mind goes while in the queue in Huber’s).

The Cleveland Clinic lists desire as the official start, with MRI studies showing increased activity in your brain’s limbic system, which causes large releases of the feel good chemicals dopamine, norepnephrine and serotonin (the same chemicals that are released at the start of a relationship). Oxytocin — or the cuddle hormone — also kicks off, and this is the reason why people want to snuggle after sex, due to the increased desire for security and connection.  

 “During the desire phase, sexual activity is at a survival level for procreation and the continuation of our species,” Maria explains. “Our brains release feel-good chemicals, so we want to keep doing it.”

Meanwhile, physical changes in the body include:

  • Muscle tension increases

  • Your heart rate quickens, and breathing is accelerated

  • Skin may become flushed (blotches of redness appear on the chest and back)

  • Nipples become hardened or erect

  • Blood flow increases to the genitals, resulting in swelling of the woman’s clitoris and labia minora (inner lips), and erection of the man’s penis

  • Vaginal lubrication begins

  • The woman’s breasts become fuller and the vaginal walls swell

  • The man’s testicles swell, his scrotum tightens, and he begins secreting a lubricating liquid

Fireworks signifying an explosive orgasm

Sexual response phase 2: Plateau

Now’s the time to ramp up the action.

Surprisingly, sex doesn’t burn off as many calories per session as you might think, with researchers finding a total of 101 calories burned for men and just 69 calories burned from women, averaging 3.6 calories per minute. No matter, because “by now, there will be a multitude of physiological responses occurring in the body, although not necessarily at the same time,” says Maria.

  • The woman’s clitoris becomes highly sensitive (even painful to touch)

  • The man’s testicles withdraw up into the scrotum

  • Breathing, heart rate and blood pressure increase

  • Muscle spasms can begin in your feet, face and hands

  • Tension in the muscles increases

  • The vagina continues to swell from increased blood flow, and the vaginal walls turn a dark purple

  • Dopamine, norepinephrine and serotonin continue to rise

You may also feel like you’ve entered something of a meditative state, which would be about right as studies have shown that intercourse and meditation light up similar areas in the brain. “Both help you to you feel more blissed out, at one with yourself and with the world,” confirms Maria. “They create a sense of limitless physical boundary and a reduction of pain which is part of how we scientifically define pleasure.”

Sexual response phase 3: Orgasm

While you don't need to have an orgasm to find sex pleasurable or to reap all of the health benefits, it's definitely a bonus. Indeed, research has found that during orgasm, the part of the brain responsible for reason, decision making and judgments temporarily shuts down and fear and anxiety decreases.

Physically, it’s all going on:

  • In women, the muscles of the vagina contract and the uterus undergoes rhythmic contractions

  • In men, rhythmic contractions of the muscles at the base of the penis result in the ejaculation

  • A rash or ‘sex flush’ may appear over the entire body.

  • Involuntary muscle contractions begin

  • Blood pressure, heart rate and breathing are at their highest, and there is a rapid intake of oxygen

  • There’s a sudden release of sexual tension

couple kissing tendering before intercourse, benefits of sex

Sexual response phase 4: Resolution

Post-sex, everything from your heart rate to your breasts to your chemical levels of dopamine slowly return back to their regular size and state.

Says Maria; “While laying post-coital, take a moment to consider how you’ve just given your immune system a boost, strengthened your heart with a cardiovascular workout, increased collagen due to the release of estrogen and reduced stress and lifted your mood thanks to all the positive hormone production. Also, you’ve protected yourself against Alzheimer’s and osteoporosis.”

And, as men who have intercourse twice a week regularly have less heart attacks than those who don’t have regular sex, you don’t have any excuses not to get into bed for round two.

Yay, sex!


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