Sparks fly, Stomach jumps, Heart thumps, Palms sweat and Nerves jitter, Y? y? y?

When sparks fly between two people, we're quick to say they have "chemistry." Not everyone realizes that such couples literally have do have chemistry--it's what's behind those sweaty palms, the jumpy stomach, thumping heart, and nervous jitters. Chemistry also contributes to that warm, comfortable feeling you get from being with a longtime partner.

In the mid-1960's, psychologist Dorothy Tennov surveyed 400 people about what it's like to be in love. Many of her respondents talked about fear, shaking, flushing, weakness, and stammering. Indeed, when human beings are attracted to one another, it sets off quite a chain reaction in the body and brain. But there's a perfectly logical explanation to those intense feelings.

The most well-known love-related chemical is phenylethylamine -- or "PEA" -- a naturally occurring trace ammine in the brain. PEA is a natural amphetamine, like the drug, and can cause similar stimulation. This natural upper contributes to that kick-up-your-heels, on-top-of-the-world feeling that attraction can bring, and gives you the energy to stay up all night talking to a new love. Sometimes this energy translates into the triple-espresso jitters; other times it simply keeps you wide-eyed and alert long past the time when you'd usually be yawning. "I always get excited about somebody who can keep me up late at night," says Elan Freydenson of New Jersey. "I really value my sleep."

The Feeling

You can also get a non-romantic dose of PEA from high-intensity activities like skydiving, or by eating chocolate. According to Chocolate.org, chocolate contains small amounts of our love drug, PEA. That might be why some people use chocolate as "comfort food," getting the same warm, relaxed feeling from chocolate as others do from Mom's chicken soup.

One of the substances released by PEA is the neurochemical dopamine. A recent study done at Emory University shows that female voles (small rodents) choose their mates in response to dopamine being released in their brains. When injected with dopamine in a male vole's presence, the female will pick him out of a crowd later. Our love food, chocolate, also elevates levels of dopamine in the brain.

In turn, Dopamine stimulates the production of oxytocin, sometimes known as "the cuddle chemical." Oxytocin is best known for its role in mothering, stimulating contractions during labor and aiding with breast feeding. According to BirthPsychology.com scientists now think that both genders release this nurturing hormone when touching and cuddling, with the oxytocin level peaking during orgasm.

Another euphoria-inducing chemical in your brain, norepinephrine, stimulates the production of adrenaline and makes your blood pressure soar when near the person you're attracted to. That's why you might experience a pounding heart or sweaty palms when you see someone you've got the hots for. 

What The Brain Tells the Body

How do our emotions get translated into physical sensations? A U.S. News and World Report article explains the importance of the vagus, a nerve that threads through your whole body. It transports signals from your brain to your organs, "setting the heart pounding, making the stomach do flip-flops, and of course, lighting the loins on fire." Everyone knows that jumpy, sort of sick feeling in your stomach. Some people call it a "hollow" feeling, while Elan Freydenson describes it this way: "That weird feeling falls somewhere between my belly button and my heart. It feels like tension building, yet it feels great and I want to have that feeling more often."

Tennov's group also reported "intrusive thinking," where it seems like your brain is fixated on the object of your affection. When your heart rules your head, there's actually one part of your brain running the other: the cortex is the area of your brain that controls logical thinking, while emotions are processed by the limbic system. When too many happy chemicals like PEA and dopamine flood your brain, they head straight for the limbic system.

The Four years Itch

Some scientists believe that after a certain period, from 18 months to 4 years, one's body gets used to these love stimulants. After building up a tolerance to uppers like PEA, passionate romances can cool into what Helen Fisher, author of "Anatomy of Love" calls "attachment." In this phase of the relationship, your brain produces endorphins, brain opiates more like morphine than speed. "Unlike PEA," says Fisher, "they calm the mind, kill pain, and reduce anxiety." So what some people call "separation anxiety" might actually be a form of drug withdrawal.

The idea that the "honeymoon period" of a relationship is fueled by different brain chemistry than what is present during the mellower years that come later might explain why some people can't seem to hold long-term relationships: they prefer the revving-up affects of brain amphetamines to the pain-killing effects of endorphins.

"Divorce rates peak around the fourth year of marriage," says Charles Panati in his book "Sexy Origins and Intimate Things." "The initial 'highs' of love have lost their chemical underpinnings Marilyn Monroe's classic film "The Seven Year Itch" should be retitled 'The Four Year Itch." 

Lynn Harris, co-creator of BreakupGirl.com wonders if it's the other way around. "Relationships take work. They just do. And people get lazy after a while," she says. "So do they get lazy because they're getting immune to the chemicals, or do they get lazy because they just do...which triggers a decline in the chemicals?"

In the end, even hard-core scientists agree that chemistry isn't everything. Culture, circumstances, personality, and scores of other variables help decide who turns your head and who leaves you cold. So don't try to reproduce that lovin' feeling in a basement chemistry lab--but do try your best to enjoy the natural highs that life gives you.

The Chemistry of =L-O-V-E=

Chemistry of Love

There are a lot of chemicals racing around your brain and body when you're in love. Researchers are gradually learning more and more about the roles they play both when we are falling in love and when we're in long-term relationships. Of course, estrogen and testosterone play a role in the sex drive area, without them, we might never venture into the "real love" arena.

That initial giddiness that comes when we're first falling in love includes a racing heart, flushed skin and sweaty palms. Researchers say this is due to the dopamine, norepinephrine and phenylethylamine we're releasing. Dopamine is thought to be the "pleasure chemical," producing a feeling of bliss.Norepinephrine is similar to adrenaline and produces the racing heart and excitement. According to Helen Fisher, anthropologist and well-known love researcher from Rutgers University, together these two chemicals produce elation, intense energy, sleeplessness, craving, loss of appetite and focused attention. She also says, "The human body releases the cocktail of love rapture only when certain conditions are met and ... men more readily produce it than women, because of their more visual nature."

Researchers are using functional magnetic resonance imaging (FMRI) to watch people's brains when they look at a photograph of their object of affection. According to Helen Fisher, a well-known love researcher and an anthropologist at Rutgers University, what they see in those scans during that "crazed, can't-think-of-anything-but stage of romance" -- the attraction stage -- is the biological drive to focus on one person. The scans showed increased blood flow in areas of the brain with high concentrations of receptors for dopamine -- associated with states of euphoria, craving and addiction. High levels of dopamine are also associated with norepinephrine, which heightens attention, short-term memory, hyperactivity, sleeplessness and goal-oriented behavior. In other words, couples in this stage of love focus intently on the relationship and often on little else.

Another possible explanation for the intense focus and idealizing view that occurs in the attraction stage comes from researchers at University College London. They discovered that people in love have lower levels of serotonin and also that neural circuits associated with the way we assess others are suppressed. These lower serotonin levels are the same as those found in people with obsessive-compulsive disorders, possibly explaining why those in love "obsess" about their partner.

Chemical Bonding

In romantic love, when two people have sex,oxytocin is released, which helps bond the relationship. According to researchers at the University of California, San Francisco, the hormone oxytocin has been shown to be "associated with the ability to maintain healthy interpersonal relationships and healthy psychological boundaries with other people." When it is released during orgasm, it begins creating an emotional bond -- the more sex, the greater the bond. Oxytocin is also associated with mother/infant bonding, uterine contractions during labor in childbirth and the "let down" reflex necessary for breastfeeding.

Vasopressin, an antidiuretic hormone, is another chemical that has been associated with the formation of long-term, monogamous relationships. Dr. Fisher believes that oxytocin and vasopressin interfere with the dopamine and norepinephrine pathways, which might explain why passionate love fades as attachment grows.

Endorphins, the body's natural painkillers, also play a key role in long-term relationships. They produce a general sense of well-being, including feeling soothed, peaceful and secure. Like dopamine and norepinephrine, endorphins are released during sex; they are also released during physical contact,exercise and other activities. According to Michel Odent of London's Primal Health Research Center, endorphins induce a "drug-like dependency."

The Long Haul?????

What about when that euphoric feeling is gone? According to Ted Huston at the University of Texas, the speed at which courtship progresses often determines the ultimate success of the relationship. What they found was that the longer the courtship, the stronger the long-term relationship.

The feelings of passionate love, however, do lose their strength over time. Studies have shown that passionate love fades quickly and is nearly gone after two or three years. The chemicals responsible for "that lovin' feeling" (adrenaline, dopamine, norepinephrine, phenylethylamine, etc.) dwindle. Suddenly your lover has faults. Why has he or she changed, you may wonder. Actually, your partner probably hasn't changed at all; it's just that you're now able to see him or her rationally, rather than through the blinding hormones of infatuation and passionate love. At this stage, the relationship is either strong enough to endure, or the relationship ends. I

f the relationship can advance, then other chemicals kick in. Endorphins, for example, are still providing a sense of well-being and security. Additionally, oxytocin is still released when you're having sex, producing feelings of satisfaction and attachment. Vasopressin also continues to play a role in attachment.

Are humans alone in Love???

Only three percent of mammals (aside from the human species) form "family" relationships like we do. The prairie vole is one such animal. This vole mates for life and prefers spending time with its mate over spending time with any other voles. Voles even go to the extreme of avoiding voles of the opposite sex.

When they have offspring, the couple works together to care for them. They spend hours grooming each other and just hanging out together. Studies have been done to try to determine the chemical makeup that might explain why the prairie vole forms this lifelong, monogamous relationship when its very close relative, the montane vole, does not.

According to studies by Larry Young, a social attachment researcher at Emory University, what happens is that when the prairie vole mates, like humans, the hormones oxytocin and vasopressin are released. Because the prairie vole has the needed receptors in its brain for these hormones in the regions responsible for reward and reinforcement, it forms a bond with its mate. That bond is for that particular vole based on its smell -- sort of like an imprint. As further reinforcement, dopamine is also released in the brain's reward center when they have sex, making the experience enjoyable and ensuring that they want to do it again. And because of the oxytocin and vasopressin, they want to have sex with the same vole.

Because the montane vole does not have receptors for oxytocin or vasopressin in its brain, those chemicals have no effect, and they continue with their one-night stands. Other than those receptors, the two vole species are almost entirely the same in their physical make up.