Neurotransmitters are chemicals that the brain produces.
Each neurotransmitter is responsible for different aspects from muscle control to memory to allergic reactions. In his Psychology Today article “What Science Tells Us about Being in Love,” science and technical author David DeSilvo notes that when a person is falling in love, two main neurotransmitters are affected. Dopamine, referred to as the “pleasure chemical,” increases, providing a feeling similar to the high of narcotics, which can make you feel almost addicted to the person. Serotonin, which protects against anxiety, drops, making you feel more unsure and unstable. This insecurity and lack of control may lead to a fixation on things that you feel are outside of your control, resulting in a type of obsession with the person.
Hormones play a large part in emotional and behavioral response.
Norepinephrine, a stress hormone, increases when you are crushing on someone; this makes your heart race, your blood pressure increase and your hands sweat when you are near her. Oxytocin, called the “bonding hormone” or the “love hormone," responsible for bonding and monogamy, increases. Oxytocin makes you want to be only with her – and makes you want her want to be only be with you.
Different parts of the brain become more or less active while dating, writes neurologist Sultan Tarlaci in his "NeuroQuantology" research article "The Brain in Love: Has Neuroscience Stolen the Secret of Love?" The prefrontal cortex, the part of the brain responsible for logical reasoning, decreases in activity.
The amygdala, responsible for fear and threat responses, also shows decreased activity. Decreases in these two regions result in more impulsive, risk-taking behavior.
Hutchens, author of “Brain Brilliant Dating,” believes that dating has to do with the three levels of the brain. The most primitive level of the brain, the reptilian part, is responsible for basic survival. In dating, it creates curiosity and lust. The mammalian level of the brain is responsible for emotions. The mammalian level controls feelings of confidence and security in being with another person. The highest level is the neocortex – of which the prefrontal cortex is a part – which creates intellectual interests and allows for communication. Hutchens notes that when all three levels of the brain are stimulated simultaneously, you experience a "mental orgasm" -- an excellent connection with the other person.