Science of Sex: Physiology of Orgasm

Welcome to the eleventh! installment in a feature on Of Sex and Love: Science of Sex. In this monthly segment, I discuss the science of sexuality in an easy-to-digest format that’s accessible to the casual reader. I will also follow up with some extended reading material for people who want to know more about the subject of each post.

It’s hard to follow up last month’s Science of Sex post, in which I lauded over a dozen women who have worked to study sex and educate the world about sexuality, But the second Saturday of this month has already passed. I had better get on it!

So I thought I’d discuss some of the physiological changes that occur during and after orgasm, changes that researchers have used to determine whether orgasm has occurred and help to explain some of the benefits of orgasm from sex or masturbation. This will more or less be a list of the changes in the body and brain due to orgasm.

Enjoy!

Physiology of Orgasm

Much of the research into orgasm and physiological changes has focused on women, perhaps because ejaculation makes it easier to determine when a man has had an orgasm. Researchers compare measurements with self-reports of orgasm.

Traditionally, heart rate has been measured to determine if orgasm has occurred, and both vaginal and clitoral orgasms increase heart rate. More intense orgasms may lead to greater increases in heart rate.

Although many of these studies focus on women, few of them have involves fMRIs. One study did look at the female brain during orgasm, finding that activity increased in several areas: sensory, motor, reward, frontal cortical, and brainstem regions. Another test found that men experience increased blood flow in several brain areas after orgasm: the visual cortex, ventral tegmental area (VTA), and ventrolateral thalamus. Blood flow decreased to the prefrontal cortex, however. In patients with epilepsy, the temporal lobe becomes essential for achieving orgasm.

EEGs have previously been used to look at brain activity during orgasm. In one study, participants masturbated to orgasm, and EEG results showed changes in brain laterality. Typically, activity increased significantly in the right hemisphere with smaller increases in the left hemisphere. Interestingly, one left-handed participant exhibited the opposite change in laterality.

Contraction of the PC muscles is another method of determining orgasm, and research has found that rectal pressure is a reliable indicator of orgasm in healthy women. Anal contractions also indicate orgasm in men.

Various chemicals and hormones increase after orgasm. Catecholamines, which include epinephrine, (adrenaline) norepinephrine, and dopamine increase in the body. Prolactin, the protein that helps female mammals breastfeed, increases because of orgasm, even in men. This may help regular sex drive after orgasm.

Men who experienced orgasm after a period of orgasmic inactivity may see an increase in testosterone in their systems after resuming masturbation.

Researchers have found that endocannabinoid levels, specifically endocannabinoid 2-AG, increase in both men and women after orgasm. You may be more familiar with endocannabinoids as they relate to marijuana. Because pot contains a chemical similar to endocannabinoid, THC, it activates the endocannabinoid system. Endocannabinoids help to regulate mood, sleep, pain, and pleasure/rewards, among other functions. Increased endocannabinoids 2-AG after orgasm may help to explain boost to mood, improved sleep and decreased pain perception.

Finally, orgasm can produce behaviors and experiences that you wouldn’t typically consider to be related to sexuality, several of which I have experienced myself. One study combined the phenomena from various case studies, cataloging the following phenomena;

cataplexy (weakness), crying, dysorgasmia, dysphoria, facial and/or ear pain, foot pain, headache, pruritus [itching of the skin], laughter, panic attack, post-orgasm illness syndrome, seizures, and sneezing.

With the profound effect that orgasm has on a person’s physiology, the vast array of effects aren’t really so surprising.

Further Reading

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